assignment for blood

18.1 An Overview of Blood

Learning objectives.

By the end of this section, you will be able to:

Identify the primary functions of blood in transportation, defense, and maintenance of homeostasis
Name the fluid component of blood and the three major types of formed elements, and identify their relative proportions in a blood sample
Discuss the unique physical characteristics of blood
Identify the composition of blood plasma, including its most important solutes and plasma proteins

Recall that blood is a connective tissue. Like all connective tissues, it is made up of cellular elements and an extracellular matrix. The cellular elements—referred to as the formed elements —include red blood cells (RBCs) , white blood cells (WBCs) , and cell fragments called platelets . The extracellular matrix, called plasma , makes blood unique among connective tissues because it is fluid. This fluid, which is mostly water, perpetually suspends the formed elements and enables them to circulate throughout the body within the cardiovascular system.

Functions of Blood

The primary function of blood is to deliver oxygen and nutrients to and remove wastes from body cells, but that is only the beginning of the story. The specific functions of blood also include defense, distribution of heat, and maintenance of homeostasis.

Transportation

Nutrients from the foods you eat are absorbed in the digestive tract. Most of these travel in the bloodstream directly to the liver, where they are processed and released back into the bloodstream for delivery to body cells. Oxygen from the air you breathe diffuses into the blood, which moves from the lungs to the heart, which then pumps it out to the rest of the body. Moreover, endocrine glands scattered throughout the body release their products, called hormones, into the bloodstream, which carries them to distant target cells. Blood also picks up cellular wastes and byproducts, and transports them to various organs for removal. For instance, blood moves carbon dioxide to the lungs for exhalation from the body, and various waste products are transported to the kidneys and liver for excretion from the body in the form of urine or bile.

Many types of WBCs protect the body from external threats, such as disease-causing bacteria that have entered the bloodstream in a wound. Other WBCs seek out and destroy internal threats, such as cells with mutated DNA that could multiply to become cancerous, or body cells infected with viruses.

When damage to the vessels results in bleeding, blood platelets and certain proteins dissolved in the plasma, the fluid portion of the blood, interact to block the ruptured areas of the blood vessels involved. This protects the body from further blood loss.

Maintenance of Homeostasis

Recall that body temperature is regulated via a classic negative-feedback loop. If you were exercising on a warm day, your rising core body temperature would trigger several homeostatic mechanisms, including increased transport of blood from your core to your body periphery, which is typically cooler. As blood passes through the vessels of the skin, heat would be dissipated to the environment, and the blood returning to your body core would be cooler. In contrast, on a cold day, blood is diverted away from the skin to maintain a warmer body core. In extreme cases, this may result in frostbite.

Blood also helps to maintain the chemical balance of the body. Proteins and other compounds in blood act as buffers, which thereby help to regulate the pH of body tissues. Blood also helps to regulate the water content of body cells.

Composition of Blood

You have probably had blood drawn from a superficial vein in your arm, which was then sent to a lab for analysis. Some of the most common blood tests—for instance, those measuring lipid or glucose levels in plasma—determine which substances are present within blood and in what quantities. Other blood tests check for the composition of the blood itself, including the quantities and types of formed elements.

One such test, called a hematocrit , measures the percentage of RBCs, clinically known as erythrocytes, in a blood sample. It is performed by spinning the blood sample in a specialized centrifuge, a process that causes the heavier elements suspended within the blood sample to separate from the lightweight, liquid plasma ( Figure 18.2 ). Because the heaviest elements in blood are the erythrocytes, these settle at the very bottom of the hematocrit tube. Located above the erythrocytes is a pale, thin layer composed of the remaining formed elements of blood. These are the WBCs, clinically known as leukocytes, and the platelets, cell fragments also called thrombocytes. This layer is referred to as the buffy coat because of its color; it normally constitutes less than 1 percent of a blood sample. Above the buffy coat is the blood plasma, normally a pale, straw-colored fluid, which constitutes the remainder of the sample.

The volume of erythrocytes after centrifugation is also commonly referred to as packed cell volume (PCV) . In normal blood, about 45 percent of a sample is erythrocytes. The hematocrit of any one sample can vary significantly, however, about 36–50 percent, according to gender and other factors. Normal hematocrit values for females range from 37 to 47, with a mean value of 41; for males, hematocrit ranges from 42 to 52, with a mean of 47. The percentage of other formed elements, the WBCs and platelets, is extremely small so it is not normally considered with the hematocrit. So the mean plasma percentage is the percent of blood that is not erythrocytes: for females, it is approximately 59 (or 100 minus 41), and for males, it is approximately 53 (or 100 minus 47).

Characteristics of Blood

When you think about blood, the first characteristic that probably comes to mind is its color. Blood that has just taken up oxygen in the lungs is bright red, and blood that has released oxygen in the tissues is a more dusky red. This is because hemoglobin is a pigment that changes color, depending upon the degree of oxygen saturation.

Blood is viscous and somewhat sticky to the touch. It has a viscosity approximately five times greater than water. Viscosity is a measure of a fluid’s thickness or resistance to flow, and is influenced by the presence of the plasma proteins and formed elements within the blood. The viscosity of blood has a dramatic impact on blood pressure and flow. Consider the difference in flow between water and honey. The more viscous honey would demonstrate a greater resistance to flow than the less viscous water. The same principle applies to blood.

The normal temperature of blood is slightly higher than normal body temperature—about 38 °C (or 100.4 °F), compared to 37 °C (or 98.6 °F) for an internal body temperature reading, although daily variations of 0.5 °C are normal. Although the surface of blood vessels is relatively smooth, as blood flows through them, it experiences some friction and resistance, especially as vessels age and lose their elasticity, thereby producing heat. This accounts for its slightly higher temperature.

The pH of blood averages about 7.4; however, it can range from 7.35 to 7.45 in a healthy person. Blood is therefore somewhat more basic (alkaline) on a chemical scale than pure water, which has a pH of 7.0. Blood contains numerous buffers that actually help to regulate pH.

Blood constitutes approximately 8 percent of adult body weight. Adult males typically average about 5 to 6 liters of blood. Females average 4–5 liters.

Blood Plasma

Like other fluids in the body, plasma is composed primarily of water: In fact, it is about 92 percent water. Dissolved or suspended within this water is a mixture of substances, most of which are proteins. There are literally hundreds of substances dissolved or suspended in the plasma, although many of them are found only in very small quantities.

Interactive Link

Visit this site for a list of normal levels established for many of the substances found in a sample of blood. Serum, one of the specimen types included, refers to a sample of plasma after clotting factors have been removed. What types of measurements are given for levels of glucose in the blood?

Plasma Proteins

About 7 percent of the volume of plasma—nearly all that is not water—is made of proteins. These include several plasma proteins (proteins that are unique to the plasma), plus a much smaller number of regulatory proteins, including enzymes and some hormones. The major components of plasma are summarized in Figure 18.3 .

The three major groups of plasma proteins are as follows:

Albumin is the most abundant of the plasma proteins. Manufactured by the liver, albumin molecules serve as binding proteins—transport vehicles for fatty acids and steroid hormones. Recall that lipids are hydrophobic; however, their binding to albumin enables their transport in the watery plasma. Albumin is also the most significant contributor to the osmotic pressure of blood; that is, its presence holds water inside the blood vessels and draws water from the tissues, across blood vessel walls, and into the bloodstream. This in turn helps to maintain both blood volume and blood pressure. Albumin normally accounts for approximately 54 percent of the total plasma protein content, in clinical levels of 3.5–5.0 g/dL blood.
The second most common plasma proteins are the globulins . A heterogeneous group, there are three main subgroups known as alpha, beta, and gamma globulins. The alpha and beta globulins transport iron, lipids, and the fat-soluble vitamins A, D, E, and K to the cells; like albumin, they also contribute to osmotic pressure. The gamma globulins are proteins involved in immunity and are better known as antibodies or immunoglobulins . Although other plasma proteins are produced by the liver, immunoglobulins are produced by specialized leukocytes known as plasma cells. (Seek additional content for more information about immunoglobulins.) Globulins make up approximately 38 percent of the total plasma protein volume, in clinical levels of 1.0–1.5 g/dL blood.
Fibrinogen is the third of the three major groups of plasma proteins. Like albumin and the alpha and beta globulins, fibrinogen is produced by the liver. It is essential for blood clotting, a process described later in this chapter. Fibrinogen accounts for about 7 percent of the total plasma protein volume, in clinical levels of 0.2–0.45 g/dL blood.

Other Plasma Solutes

In addition to proteins, plasma contains a wide variety of other substances. These include various electrolytes, such as sodium, potassium, and calcium ions; dissolved gases, such as oxygen, carbon dioxide, and nitrogen; various organic nutrients, such as vitamins, lipids, glucose, and amino acids; and metabolic wastes. All of these nonprotein solutes combined contribute approximately 1 percent to the total volume of plasma.

Career Connection

Phlebotomy and medical lab technology.

Phlebotomists are professionals trained to draw blood (phleb- = “a blood vessel”; -tomy = “to cut”). When more than a few drops of blood are required, phlebotomists perform a venipuncture, typically of a surface vein in the arm. They perform a capillary stick on a finger, an earlobe, or the heel of an infant when only a small quantity of blood is required. An arterial stick is collected from an artery and used to analyze blood gases. After collection, the blood may be analyzed by medical laboratories or perhaps used for transfusions, donations, or research. While many allied health professionals practice phlebotomy, the American Society of Phlebotomy Technicians issues certificates to individuals passing a national examination, and some large labs and hospitals hire individuals expressly for their skill in phlebotomy.

Medical or clinical laboratories employ a variety of individuals in technical positions:

Medical technologists (MT), also known as clinical laboratory technologists (CLT), typically hold a bachelor’s degree and certification from an accredited training program. They perform a wide variety of tests on various body fluids, including blood. The information they provide is essential to the primary care providers in determining a diagnosis and in monitoring the course of a disease and response to treatment.
Medical laboratory technicians (MLT) typically have an associate’s degree but may perform duties similar to those of an MT.
Medical laboratory assistants (MLA) spend the majority of their time processing samples and carrying out routine assignments within the lab. Clinical training is required, but a degree may not be essential to obtaining a position.

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Authors: J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix
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Blood Anatomy and Physiology

Dive into the life-giving essence of blood anatomy and physiology. Nursing students, here’s your roadmap to understanding the vital river that courses through us, carrying both life and messages.

Functions of the blood, physical characteristics and volume, erythrocytes, hematopoiesis, formation of red blood cells, formation of white blood cells and platelets, human blood groups, blood typing.

Blood is unique; it is the only fluid tissue in the body.

1. Carrier of gases, nutrients, and waste products. Oxygen enters blood in the lungs and is transported to cells. Carbon dioxide, produced by cells, is transported in the blood to the lungs, from which it is expelled. Ingested nutrients, ions, and water are carried by the blood from the digestive tract to cells, and the waste products of the cells are moved to the kidneys for elimination. 2. Clot formation. Clotting proteins help stem blood loss when a blood vessel is injured. 3. Transport of processed molecules. Most substances are produced in one part of the body and transported in the blood to another part. 4. Protection against foreign substances. Antibodies help protect the body from pathogens. 5. Transport of regulatory molecules. Various hormones and enzymes that regulate body processes are carried from one part of the body to another within the blood. 6. Maintenance of body temperature. Warm blood is transported from the inside to the surface of the body, where heat is released from the blood. 7. pH and osmosis regulation. Albumin is also an important blood buffer and contributes to the osmotic pressure of blood, which acts to keep water in the blood stream.

Components of Blood

Essentially, blood is a complex connective tissue in which living blood cells, the formed elements, are suspended.

Blood is a sticky, opaque fluid with a characteristic metallic taste .

Color. Depending on the amount of oxygen it is carrying, the color of blood varies from scarlet (oxygen-rich) to a dull red (oxygen-poor).
Weight. Blood is heavier than water and about five times thicker, or more viscous, largely because of its formed elements.
pH. Blood is slightly alkaline, with a pH between 7.35 and 7.45 .
Temperature. Its temperature ( 38 degrees Celsius , or 100.4 degrees Fahrenhei t) is always slightly higher than body temperature.

Plasma, which is approximately 90 percent water, is the liquid part of the blood.

Dissolved substances. Examples of dissolved substances include nutrients, salts ( electrolytes ), respiratory gases, hormones, plasma proteins, and various wastes and products of cell metabolism.
Plasma proteins. Plasma proteins are the most abundant solutes in plasma; except for antibodies and protein-based hormones, most plasma proteins are made by the liver .
Composition. The composition of plasma varies continuously as cells remove or add substances to the blood; assuming a healthy diet, however, the composition of plasma is kept relatively constant by various homeostatic mechanisms of the body.

Formed Elements

If you observe a stained smear of human blood under a light microscope, you will see disc-shaped red blood cells, a variety of gaudily stained spherical white blood cells, and some scattered platelets that look like debris.

Erythrocytes, or red blood cells, function primarily to ferry oxygen in blood to all cells of the body.

Anucleate. RBCs differ from other blood cells because they are anucleate, that is, they lack a nucleus; they also contain a very few organelles.
Hemoglobin. Hemoglobin, an iron bearing protein, transports the bulk of oxygen that is carried in the blood.
Microscopic appearance. Erythrocytes are small, flexible cells shaped like biconcave discs- flattened discs with depressed centers on both sides; they look like miniature doughnuts when viewed with a microscope.
Number of RBCs. There are normally about 5 million cells per cubic millimeter of blood; RBCs outnumber WBCs by about 1000 to 1 and are the major factor contributing to blood viscosity.
Normal blood. Clinically, normal blood contains 12-18 grams of hemoglobin per 100 milliliters (ml); the hemoglobin content is slightly higher in men (13-18 g/dl) than in women (12-16 g/dl).

Although leukocytes, or white blood cells, are far less numerous than red blood cells, they are crucial to body defense against disease.

Number of WBCs. On average, there are 4,000 to 11,000 WBC/mm3 , and they account for less than 1 percent of total body volume.
Body defense. Leukocytes form a protective, movable army that helps defend the body against damage by bacteria, viruses, parasites, and tumor cells.
Diapedesis. White blood cells are able to slip into and out of the blood vessels- a process called diapedesis.
Positive chemotaxis. In addition, WBCs can locate areas of tissue damage and infection in the body by responding to certain chemicals that diffuse from the damaged cells; this capability is called positive chemotaxis.
Ameboid motion. Once they have “caught the scent”, the WBCs move through the tissue spaces by ameboid motion (they form flowing cytoplasmic extensions that help move them along).
Leukocytosis. A total WBC count above 11, 000 cells/mm3 is referred to as leukocytosis.
Leukopenia. The opposite condition, leukopenia, is an abnormally low WBC count.
Granulocytes. Granulocytes are granule-containing WBCs; they have lobed nuclei, which typically consist of several rounded nuclear areas connected by thin strands of nuclear material, and includes neutrophils , eosinophils , and basophils .
Neutrophils. Neutrophil are the most numerous of the WBCs; they have a multilobed granules and very fine granules that respond to acidic and basic stains; neutrophils are avid phagocytes at sites of acute infection, and are particularly partial to bacteria and fungi .
Eosinophils. Eosinophils have blue red nucleus that resembles an old-fashioned telephone receiver and sport coarse, lysosome-like, brick-red cytoplasmic granules; their number increases rapidly during allergies and infections by parasitic worms or entering via the skin.
Basophils. Basophils, the rarest of the WBCs, contain large, histamine-containing granules that stain dark blue; histamine is an inflammatory chemical that makes blood vessels leaky and attracts other WBCs to the inflammatory site.
Agranulocytes. The second group of WBCs, the agranulocytes, lack visible cytoplasmic granules; their nuclei are closer to the norm- that is, they are spherical; they are spherical, oval, or kidney -shaped; and they include lymphocytes and monocytes .
Lymphocytes . Lymphocytes have a large, dark purple nucleus that occupies most of the cell volume; they tend to take up residence in lymphatic tissues, where they play an important role in the immune response.
Monocytes. Monocytes are the largest of the WBCs; when they migrate into the tissues, they transform into macrophages with huge appetites; macrophages are very important in fighting chronic infections.
Platelets. Platelets are not cells in the strict sense; they are fragments of bizarre multinucleate cells called megakaryocytes , which pinch off thousands of anucleate platelet “pieces” that quickly seal themselves off from surrounding fluids; platelets are needed for the clotting process that occurs in plasma when blood vessels are ruptured or broken.

Blood cell formation, or hematopoiesis, occurs in red bone marrow, or myeloid tissue.

Hemocytoblast. All the formed elements arise from a common type of stem cell, the hemocytoblast.
Descendants of hemocytoblasts. The hemocytoblast forms two types of descendants- the lymphoid stem cell , which produces lymphocytes, and the myeloid stem cell , which can produce all other classes of formed elements.

Because they are anucleate, RBCs are unable to synthesize proteins, grow, or divide.

Life span. As they age, RBCs become more rigid and begin to fragment, or fall apart, in 100 to 120 days .
Lost RBCs. Lost cells are replaced more or less continuously by the division of hemocytoblasts in the red bone marrow.
Immature RBCs. Developing RBCs divide many times and then begin synthesizing huge amounts of hemoglobin.
Reticulocyte. Suddenly, when enough hemoglobin has been accumulated, the nucleus and most organelles are ejected and the cell collapses inward; the result is the young RBC, called a reticulocyte because it still contains some rough endoplasmic reticulum (ER).
Mature erythrocytes. Within 2 days of release, they have rejected the remaining ER and have become fully functioning erythrocytes; the entire developmental process from hemocytoblast to mature RBC takes 3 to 5 days .
Erythropoietin. The rate of erythrocyte production is controlled by a hormone called erythropoietin ; normally a small amount of erythropoietin circulates in the blood at all times, and red blood cells are formed at a fairly constant rate.
Control of RBC production. An important point to remember is that it is not the relative number of RBCS in the blood that controls RBC production; control is based on their ability to transport enough oxygen to meet the body’s demands.

Like erythrocyte production, the formation of leukocytes and platelets is stimulated by hormones.

Colony stimulating factors and interleukins . These colony stimulating factors and interleukins not only prompt red bone marrow to turn out leukocytes, but also marshal up an army of WBCs to ward off attacks by enhancing the ability of mature leukocytes to protect the body.
Thrombopoietin. The hormone thrombopoietin accelerates the production of platelets, but little is known about how that process is regulated.

The multistep process of hemostasis begins when a blood vessel is damaged and connective tissue in the vessel wall is exposed to blood.

Vascular spasms occur. The immediate response to blood vessel injury is vasoconstriction, which causes that blood vessel to go into spasms; the spasms narrow the blood vessel, decreasing blood loss until clotting can occur.
Platelet plug forms. Injury to the lining of vessels exposes collage fibers; platelets adhere to the damaged site and platelet plug forms.
Coagulation events occur. At the same time, the injured tissues are releasing tissue factor (TF) , a substance that plays an important role in clotting; PF3 , a phospholipid that coats the surfaces of the platelets, interacts with TF, vitamin K, and other blood clotting factors; this prothrombin activator converts prothrombin , present in the plasma, to thrombin , an enzyme; thrombin then joins soluble fibrinogen proteins into long, hairlike molecules of insoluble fibrin , which forms the meshwork that traps RBCs and forms the basis of the clot; within the hour, the clot begins to retract, squeezing serum from the mass and pulling the ruptured edges of the blood vessel closer together.

Blood Groups and Transfusions

As we have seen, blood is vital for transporting substances through the body; when blood is lost, the blood vessels constrict and the bone marrow steps up blood cell formation in an attempt to keep the circulation going.

Although whole blood transfusions can save lives, people have different blood groups, and transfusing incompatible or mismatched blood can be fatal.

Antigen. An antigen is a substance that the body recognizes as foreign; it stimulates the immune system to release antibodies or use other means to mount a defense against it.
Antibodies. One person’s RBC proteins will be recognized as foreign if transfused into another person with different RBC antigens; the “recognizers” are antibodies present in the plasma that attach to RBCs bearing surface antigens different from those on the patient’s (blood recipient’s) RBCs.
Agglutination. Binding of the antibodies causes the foreign RBCs to clump, a phenomenon called agglutination, which leads to the clogging of small blood vessels throughout the body.
ABO blood groups. The ABO blood groups are based on which of two antigens, type A or type B, a person inherits; absence of both antigens results in type O blood , presence of both antigens leads to type AB , and the presence of either A or B antigen yields type A or B blood .
Rh blood groups. The Rh blood groups are so named because one of the eight Rh antigens ( agglutinogen D ) was originally identified in Rh esus monkeys; later the same antigen was discovered in human beings; most Americans are Rh+ (Rh positive), meaning that their RBCs carry the Rh antigen.
Anti-Rh antibodies. Unlike the antibodies of the ABO system, anti-Rh antibodies are not automatically formed and present in the blood of Rh- (Rh-negative) individuals.
Hemolysis. Hemolysis (rupture of RBCs) does not occur with the first transfusion because it takes time for the body to react and start making antibodies.

The importance of determining the blood group of both the donor and the recipient before blood is transfused is glaringly obvious.

Blood typing of ABO blood groups. When serum containing anti-A or anti-B antibodies is added to a blood sample diluted with saline, agglutination will occur between the antibody and the corresponding antigen.
Cross matching. Cross matching involves testing for agglutination of donor RBCs by the recipient’s serum and of the recipient’s RBCs by the donor serum;
Blood typing for Rh factors. Typing for the Rh factors is done in the same manner as ABO blood typing.

Craving more insights? Dive into these related materials to enhance your study journey!

Anatomy and Physiology Nursing Test Banks . This nursing test bank includes questions about Anatomy and Physiology and its related concepts such as: structure and functions of the human body, nursing care management of patients with conditions related to the different body systems.

8 thoughts on “Blood Anatomy and Physiology”

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Recent News

blood , fluid that transports oxygen and nutrients to the cells and carries away carbon dioxide and other waste products. Technically, blood is a transport liquid pumped by the heart (or an equivalent structure) to all parts of the body, after which it is returned to the heart to repeat the process. Blood is both a tissue and a fluid. It is a tissue because it is a collection of similar specialized cells that serve particular functions. These cells are suspended in a liquid matrix ( plasma ), which makes the blood a fluid. If blood flow ceases, death will occur within minutes because of the effects of an unfavourable environment on highly susceptible cells.

Observe how a red blood cell travels from the heart to the lungs and other body tissues to exchange oxygen and carbon dioxide

The constancy of the composition of the blood is made possible by the circulation , which conveys blood through the organs that regulate the concentrations of its components. In the lungs , blood acquires oxygen and releases carbon dioxide transported from the tissues. The kidneys remove excess water and dissolved waste products. Nutrient substances derived from food reach the bloodstream after absorption by the gastrointestinal tract . Glands of the endocrine system release their secretions into the blood, which transports these hormones to the tissues in which they exert their effects. Many substances are recycled through the blood; for example, iron released during the destruction of old red cells is conveyed by the plasma to sites of new red cell production where it is reused. Each of the numerous components of the blood is kept within appropriate concentration limits by an effective regulatory mechanism. In many instances, feedback control systems are operative; thus, a declining level of blood sugar ( glucose ) leads to accelerated release of glucose into the blood so that a potentially hazardous depletion of glucose does not occur.

Unicellular organisms, primitive multicellular animals, and the early embryos of higher forms of life lack a circulatory system . Because of their small size, these organisms can absorb oxygen and nutrients and can discharge wastes directly into their surrounding medium by simple diffusion . Sponges and coelenterates (e.g., jellyfish and hydras ) also lack a blood system; the means to transport foodstuffs and oxygen to all the cells of these larger multicellular animals is provided by water, sea or fresh, pumped through spaces inside the organisms. In larger and more-complex animals, transport of adequate amounts of oxygen and other substances requires some type of blood circulation. In most such animals the blood passes through a respiratory exchange membrane , which lies in the gills , lungs, or even the skin. There the blood picks up oxygen and disposes of carbon dioxide.

The cellular composition of blood varies from group to group in the animal kingdom. Most invertebrates have various large blood cells capable of amoeboid movement. Some of these aid in transporting substances; other are capable of surrounding and digesting foreign particles or debris ( phagocytosis ). Compared with vertebrate blood, however, that of the invertebrates has relatively few cells. Among the vertebrates, there are several classes of amoeboid cells (white blood cells, or leukocytes ) and cells that help stop bleeding ( platelets , or thrombocytes).

Oxygen requirements have played a major role in determining both the composition of blood and the architecture of the circulatory system. In some simple animals, including small worms and mollusks , transported oxygen is merely dissolved in the plasma. Larger and more-complex animals, which have greater oxygen needs, have pigments capable of transporting relatively large amounts of oxygen. The red pigment hemoglobin , which contains iron, is found in all vertebrates and in some invertebrates. In almost all vertebrates, including humans, hemoglobin is contained exclusively within the red cells ( erythrocytes ). The red cells of the lower vertebrates (e.g., birds) have a nucleus , whereas mammalian red cells lack a nucleus. Red cells vary markedly in size among mammals; those of the goat are much smaller than those of humans, but the goat compensates by having many more red cells per unit volume of blood. The concentration of hemoglobin inside the red cell varies little between species. Hemocyanin , a copper -containing protein chemically unlike hemoglobin, is found in some crustaceans . Hemocyanin is blue in colour when oxygenated and colourless when oxygen is removed. Some annelids have the iron-containing green pigment chlorocruorin, others the iron-containing red pigment hemerythrin. In many invertebrates the respiratory pigments are carried in solution in the plasma, but in higher animals, including all vertebrates, the pigments are enclosed in cells; if the pigments were freely in solution, the pigment concentrations required would cause the blood to be so viscous as to impede circulation.

This article focuses on the main components and functions of human blood. For full treatment of blood groups, see the article blood group . For information on the organ system that conveys blood to all organs of the body, see cardiovascular system . For additional information on blood in general and comparison of the blood and lymph of diverse organisms, see circulation .

Blood components

In humans, blood is an opaque red fluid, freely flowing but denser and more viscous than water. The characteristic colour is imparted by hemoglobin , a unique iron-containing protein. Hemoglobin brightens in colour when saturated with oxygen (oxyhemoglobin) and darkens when oxygen is removed (deoxyhemoglobin). For this reason, the partially deoxygenated blood from a vein is darker than oxygenated blood from an artery . The red blood cells ( erythrocytes ) constitute about 45 percent of the volume of the blood, and the remaining cells (white blood cells, or leukocytes , and platelets , or thrombocytes) less than 1 percent. The fluid portion, plasma , is a clear, slightly sticky, yellowish liquid. After a fatty meal, plasma transiently appears turbid. Within the body the blood is permanently fluid, and turbulent flow assures that cells and plasma are fairly homogeneously mixed.

The total amount of blood in humans varies with age, sex, weight, body type, and other factors, but a rough average figure for adults is about 60 millilitres per kilogram of body weight. An average young male has a plasma volume of about 35 millilitres and a red cell volume of about 30 millilitres per kilogram of body weight. There is little variation in the blood volume of a healthy person over long periods, although each component of the blood is in a continuous state of flux. In particular, water rapidly moves in and out of the bloodstream, achieving a balance with the extravascular fluids (those outside the blood vessels) within minutes. The normal volume of blood provides such an adequate reserve that appreciable blood loss is well tolerated. Withdrawal of 500 millilitres (about a pint) of blood from normal blood donors is a harmless procedure. Blood volume is rapidly replaced after blood loss; within hours, plasma volume is restored by movement of extravascular fluid into the circulation. Replacement of red cells is completed within several weeks. The vast area of capillary membrane, through which water passes freely, would permit instantaneous loss of the plasma from the circulation were it not for the plasma proteins—in particular, serum albumin . Capillary membranes are impermeable to serum albumin, the smallest in weight and highest in concentration of the plasma proteins. The osmotic effect of serum albumin retains fluid within the circulation, opposing the hydrostatic forces that tend to drive the fluid outward into the tissues.

Biology Article

Blood is one of the most important components of life. Almost any animal that possesses a circulatory system has blood. From an evolutionary perspective, blood was speculated to have risen from a type of cell that was responsible for phagocytosis and nutrition. Billions of years later, blood and the circulatory system have drastically helped the evolution of more complex lifeforms.


Blood is a fluid connective tissue that consists of plasma, blood cells and platelets. It circulates throughout our body delivering oxygen and nutrients to various cells and tissues. It makes up 8% of our body weight. An average adult possesses around 5-6 litres of blood.

Types of Blood Cells

We have seen blood consist of cells known as formed elements of blood. These cells have their own functions and roles to play in the body. The blood cells which circulate all around the body are as follows:

Red blood cells (Erythrocytes)

RBCs are biconcave cells without nucleus in humans; also known as erythrocytes. RBCs contain the iron-rich protein called haemoglobin; give blood its red colour. RBCs are the most copious blood cells produced in bone marrows. Their main function is to transport oxygen from and to various tissues and organs.

White blood cells (Leucocytes)

Leucocytes are colourless blood cells. They are colourless because it is devoid of haemoglobin. They are further classified as granulocytes and agranulocytes. WBCs mainly contribute to immunity and defence mechanism.

Red Blood Cells are red due to Hemoglobin , which is a transport molecule and also a pigment. As a result, blood is red.

Types of White Blood Cells

There are five different types of White blood cells and are classified mainly based on the presence and absence of granules.

Granulocytes

Agranulocytes.

There are five types of white blood cells present in the blood

They are leukocytes, with the presence of granules in their cytoplasm. The granulated cells include- eosinophil, basophil, and neutrophil.

Eosinophils

They are the cells of leukocytes, which are present in the immune system.

These cells are responsible for combating infections in parasites of vertebrates and for controlling mechanisms associated with allergy and asthma .

Eosinophil cells are small granulocyte, which are produced in the bone marrow and makes 2 to 3 per cent of whole WBCs. These cells are present in high concentrations in the digestive tract.

They are the least common of the granulocytes, ranging from 0.5 to 1 per cent of WBCs.

They contain large cytoplasmic granules, which play a vital role in mounting a non-specific immune response to pathogens, and allergic reactions by releasing histamine and dilating the blood vessels.

These white blood cells have the ability to be stained when exposed to basic dyes, hence referred to as basophil.

These cells are best known for their role in asthma and their result in inflammation and bronchoconstriction in the airways.

They secrete serotonin, histamine and heparin.

Neutrophils

They are normally found in the bloodstream.

They are predominant cells, which are present in pus.

Around 60 to 65 per cent of WBCs are neutrophils with a diameter of 10 to 12 micrometres.

The nucleus is 2 to 5 lobed and the cytoplasm has very fine granules.

Neutrophil helps in the destruction of bacteria with lysosomes, and it acts as a strong oxidant.

Neutrophils are stained only using neutral dyes. Hence, they are called so.

Neutrophils are also the first cells of the immune system to respond to an invader such as a bacteria or a virus.

The lifespan of these WBCs extends for up to eight hours and is produced every day in the bone marrow.

They are leukocytes, with the absence of granules in their cytoplasm. Agranulocytes are further classified into monocytes and lymphocytes.

These cells usually have a large bilobed nucleus, with a diameter of 12 to 20 micrometres.

The nucleus is generally half-moon shaped or kidney-shaped and it occupies 6 to 8 per cent of WBCs.

They are the garbage trucks of the immune system.

The most important functions of monocytes are to migrate into tissues and clean up dead cells, protect against bloodborne pathogens and move very quickly to the sites of infections in the tissues .

These white blood cells have a single bean-shaped nucleus, hence referred to as Monocytes.

Lymphocytes

They play a vital role in producing antibodies.

Their size ranges from 8 to 10 micrometres.

They are commonly known as natural killer cells.

They play an important role in body defence.

These white blood cells are colourless cells formed in lymphoid tissue, hence referred to as lymphocytes.

There are two main types of lymphocytes – B lymphocytes and T lymphocytes.

These cells are very important in the immune systems and are responsible for humoral and cell-mediated immunity.

Platelets (Thrombocytes)

Thrombocytes are specialized blood cells produced from bone marrow.

Platelets come into play when there is bleeding or haemorrhage.

They help in clotting and coagulation of blood. Platelets help in coagulation during a cut or wound.

Composition of Blood: Plasma, RBCs, WBCs and platelets

Components Of Blood

There are many cellular structures in the composition of blood. When a sample of blood is spun in a centrifuge machine, they separate into the following constituents: Plasma, buffy coat and erythrocytes. Thus blood contains RBC, WBC, platelets and plasma.

The liquid state of blood can be contributed to plasma as it makes up ~55% of blood. It is pale yellow in colour and when separated. Blood plasma consists of salts, nutrients, water and enzymes. Blood plasma also contains important proteins and other components necessary for overall health. Hence, blood plasma transfusions are given to patients with liver failure and life-threatening injuries.

Components of Blood Plasma

Blood plasma has several protein components. Proteins in blood plasma are:

Serum globulin
Serum albumin

The serum contains only globulin and albumin. Fibrinogen is absent in serum because it is converted into fibrin during blood clotting.

Red Blood Cells (RBC)

Red blood cells consist of Haemoglobin, a protein. They are produced by the bone marrow to primarily carry oxygen to the body and carbon dioxide away from it.

White Blood Cells (WBC)

White blood cells are responsible for fighting foreign pathogens (such as bacteria, viruses, and fungi) that enter our body. They circulate throughout our body and originate from the bone marrow.

Tiny disc-shaped cells that help regulate blood flow when any part of the body is damaged, thereby aiding in fast recovery through clotting of blood.

The above-stated elements form the composition of blood in humans. The only vertebrate without haemoglobin is the crocodile icefish. It derives its oxygen requirement directly from the cold, oxygen-rich water where it lives.

Also Read: Difference between Plasma and Serum

Blood Vessels

There are different types of blood vessels in our body each carrying out specialized functions.

Blood vessels are categorized into arteries, veins and capillaries

Types of Blood Vessels

Three types of blood vessels are:

Capillaries

Arteries are strong tubes and muscular in nature. These blood vessels carry oxygen-rich blood from the heart to all the tissues of the body. Aorta is one of the main arteries that arise from the heart and branches further.

Veins are elastic blood vessels which carry deoxygenated blood from all parts of the body to the heart. An exception is the umbilical and pulmonary veins. The Pulmonary vein carries oxygenated blood to the heart from the lungs and the umbilical vein carries oxygenated blood from the placenta to the foetus.

On reaching tissues, arteries branch further into extremely thin tubes called capillaries. Capillaries bring about the exchange of substances between blood and tissues.

Sinusoids are a special type of wider capillaries present in bone marrow, liver, lymph nodes, spleen and some endocrine glands. They may be continuous, discontinuous or fenestrated.

Layers of Blood Vessels

Both arteries and veins consist of three layers.

Tunica Intima : It is one of the innermost and thinnest layers of arteries and veins. It comprises endothelial cells. They are in direct contact with the flow of blood.

Tunica Media : It is the middle layer of an artery or vein. Tunica media is made up of smooth muscle cells.

Tunica Externa: It surrounds tunica media. It is made up of collagen and is also supported by the elastic lamina in arteries.

Functions of Blood

Blood is responsible for the following body functions:

Fluid Connective Tissue

Blood is a fluid connective tissue composed of 55% plasma and 45% formed elements including WBCs, RBCs, and platelets. Since these living cells are suspended in plasma, blood is known as a fluid connective tissue and not just fluid.

Provides oxygen to the cells

Blood absorbs oxygen from the lungs and transports it to different cells of the body. The waste carbon dioxide moves from the blood to the lungs and is exhaled.

Transports Hormones and Nutrients

The digested nutrients such as glucose, vitamins, minerals, and proteins are absorbed into the blood through the capillaries in the villi lining the small intestine.

The hormones secreted by the endocrine glands are also transported by the blood to different organs and tissues.

Homeostasis

Blood helps to maintain the internal body temperature by absorbing or releasing heat.

Blood Clotting at Site of Injury

The platelets help in the clotting of blood at the site of injury. Platelets along with the fibrin form clot at the wound site

Transport of waste to the Kidney and Liver

Blood enters the kidney where it is filtered to remove nitrogenous waste out of the blood plasma. The toxins from the blood are also removed by the liver.

Protection of the body against pathogens

The White Blood Cells fight against infections. They multiply rapidly during infections.

To know more about blood, its types, blood vessels, and composition of blood, please register at BYJU’S or download the BYJU’S app for further reference.

More to Explore:

Difference Between Blood and Lymph
Blood Groups

Frequently Asked Questions

1. what is blood, 2. state the types of blood cells found in human blood..

Blood cells are classified into the following types:

Erythrocytes or red blood cells
Leucocytes or white blood cells

3. State the different types of white blood cells found in the blood.

White blood cells can be classified as follows:

lymphocytes
neutrophils
eosinophils

4. What are granulocytes?

Granulocytes are leukocytes with granule-like structures, that contain enzymes capable of digesting microorganisms. Granulocytes are further classified into eosinophils, basophils, and neutrophils.

5. What are agranulocytes?

Agranulocytes are a type of white blood cell that has no distinct granules in their cytoplasm. However, they form an important part of the body’s immune system. They are further classified into monocytes and lymphocytes.

6. Name the various components of blood.

Blood is primarily broken down into the following components:

7. What are the various types of blood vessels present in our body?

Blood vessels are classified as follows:

8. What are sinusoids?

Sinusoids are very small vessels predominantly located inside the bone marrow, liver and spleen. Sinusoids are usually a little larger than capillaries.

9. Name the various layers of blood vessels.

Tunica Intima
Tunica Media
Tunica Adventitia or Externa

10. Name the major functions of blood.

Helps in homeostasis
Transports hormones and nutrients
Help in the clotting process

11. What gives blood its red colour?

12. does plasma contain haemoglobin.

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18.1 Functions of Blood

Learning objectives.

By the end of this section, you will be able to:

Identify the primary functions of blood, its fluid and cellular components, and its characteristics

Identify the primary functions of blood in transportation, defense, and maintenance of homeostasis
Identify the primary proteins and other solutes present in blood plasma
Name the fluid component of blood and the three major types of formed elements, and identify their relative proportions in a blood sample

Recall that blood is a connective tissue. Like all connective tissues, it is made up of cellular elements and an extracellular matrix. The cellular elements—referred to as the formed elements —include red blood cells (RBCs) , white blood cells (WBCs) , and cell fragments called platelets . The extracellular matrix, called plasma , makes blood unique among connective tissues because it is fluid. This fluid, which is mostly water, suspends the formed elements and enables them to circulate throughout the body within the cardiovascular system.

Functions of Blood

The primary function of blood is to deliver oxygen and nutrients to, and remove wastes from, the body cells; but that is only the beginning of the story. The specific functions of blood also include defense, and maintenance of homeostasis, such as distributing heat where it is needed.

Transportation

Nutrients from the foods you eat are absorbed in the digestive tract. Most of these travel in the bloodstream directly to the liver, where they are processed and released back into the bloodstream for delivery to body cells. Oxygen from the air you breathe diffuses into the blood, which moves from the lungs to the heart, which then pumps it to the rest of the body. Moreover, endocrine glands scattered throughout the body release hormones into the bloodstream, which carries them to distant target cells. Blood also picks up cellular wastes and byproducts, and transports them to various organs for removal. For instance, blood moves carbon dioxide to the lungs for exhalation from the body, and various waste products are transported to the kidneys and liver for excretion from the body in the form of urine or bile.

When damage to the vessels results in bleeding, blood platelets and certain proteins dissolved in the plasma, interact to create clots which block the ruptured areas of the blood vessels involved. This protects the body from further blood loss.

Maintenance of Homeostasis

Recall that body temperature is regulated via a negative-feedback loop. If you were exercising on a warm day, your rising core body temperature would trigger several homeostatic mechanisms, including increased transport of blood from your core to your body periphery, which is typically cooler. As blood passes through the vessels of the skin, heat would be dissipated to the environment, and the blood returning to your body core would be cooler. In contrast, on a cold day, blood is diverted away from the skin to maintain a warmer body core. In extreme cases, this may result in frostbite.

Blood also helps to maintain the chemical balance of the body. Proteins and other compounds in blood act as buffers, which help to regulate the pH of body tissues. Blood also helps to regulate the water content of body cells because it has large proteins that exert osmotic pressure, which resist excessive fluid loss from the blood.

Composition of Blood

If you have had a blood test, it was likely drawn from a superficial vein in your arm, which was then sent to a lab for analysis. Some of the most common blood tests—for instance, those measuring lipid or glucose levels in plasma—determine which substances are present within blood and in what quantities. Other blood tests check for the composition of the blood itself, including the quantities and types of formed elements.

One such test examines hematocrit, which measures the percentage of RBCs (erythrocytes) in a blood sample. It is performed by spinning the blood sample in a specialized centrifuge, a process that causes the heavier elements suspended within the blood sample to separate from the lightweight, liquid plasma ( Figure 18.1.1 ). Because the densest elements in blood are the erythrocytes, these settle at the bottom of the hematocrit tube. Located above the erythrocytes is a pale, thin layer composed of the remaining formed elements of blood. These are the WBCs (leukocytes) and the platelets (thrombocytes). This layer is referred to as the buffy coat, and it normally constitutes less than 1 percent of a blood sample. Above the buffy coat is the blood plasma, normally a pale, straw-colored fluid, which constitutes the remainder of the sample.

The volume of erythrocytes after centrifugation is also commonly referred to as packed cell volume . Typically, blood contains about 45 percent erythrocytes, however, samples can vary significantly from about 36–50 percent. Normal hematocrit values for females range from 37 to 47%, with a mean value of 41%; for males, hematocrit ranges from 42 to 52%, with a mean of 47%. The percentage of other formed elements, the WBCs and platelets, is extremely small so it is not normally considered with the hematocrit. Therefore, the mean plasma percentage is the percent of blood that is not erythrocytes: for females, approximately 59% (or 100 minus 41), and for males, approximately 53% (or 100 minus 47).

This figure shows three test tubes with a red and yellow liquid in them. The left panel shows normal blood, the center panel shows anemic blood and the right panel shows polycythemic blood.

Characteristics of Blood

When you think about blood, the first characteristic that probably comes to mind is its color. Blood that has just taken up oxygen in the lungs is bright red, and blood that has released oxygen in the tissues is a darker red. This is because hemoglobin is a pigment that changes color, depending upon the degree of oxygen saturation.

Blood is viscous, with a viscosity approximately five times greater than water. Viscosity is a measure of a fluid’s thickness or resistance to flow, and is influenced by the presence of the plasma proteins and formed elements within the blood. The viscosity of blood has a dramatic impact on blood pressure and flow. Consider the difference in flow between water and honey. The more viscous honey would demonstrate a greater resistance to flow than the less viscous water. The same principle applies to blood. Blood viscosity is inversely proportional to hydration; the more hydrated you are, the less viscous your blood becomes. In severely dehydrated individuals, blood can become excessively viscous sometimes resulting in infarction or other cardiovascular events.

The normal temperature of blood is slightly higher than normal body temperature—about 38 °C (or 100.4 °F), compared to 37 °C (or 98.6 °F) for an internal body temperature reading. Although the surface of a blood vessel is relatively smooth, blood experiences friction and resistance to its flow. This produces heat, accounting for the slightly higher temperature of blood.

Blood constitutes approximately 8 percent of adult body weight. Adult males typically average about 5-6 liters of blood, and females average 4–5 liters.

Blood Plasma

Plasma is 92% water. Dissolved or suspended within this water is a mixture of substances, most of which are proteins. There are hundreds of substances dissolved in the plasma, although many of them are found only in very small quantities.

External Website

Plasma Proteins

Approximately 7 percent of the plasma is made of proteins. These include several plasma proteins (proteins that are unique to the plasma), plus a much smaller number of regulatory proteins, including enzymes and hormones. The major components of plasma are summarized in Figure 18.1.2 .

The three major groups of plasma proteins are as follows:

Albumin is the most abundant of the plasma proteins. Manufactured by the liver, albumin molecules serve as binding proteins—transport vehicles for fatty acids and steroid hormones. Recall that lipids are hydrophobic; however, binding to albumin enables their transport in the watery plasma. Albumin is also the most significant contributor to the osmotic pressure of blood; that is, its presence holds water inside the blood vessels and draws water from the tissues, across blood vessel walls, and into the bloodstream. This in turn helps to maintain both blood volume and blood pressure. Albumin normally accounts for approximately 54 percent of the total plasma protein content, or 3.5–5.0 g/dL of blood.
The second most common plasma proteins are the globulins . A heterogeneous group, there are three main subgroups known as alpha, beta, and gamma globulins. The alpha and beta globulins transport iron, lipids, and the fat-soluble vitamins A, D, E, and K to the cells; like albumin, they also contribute to osmotic pressure. The gamma globulins are proteins involved in immunity and are better known as an antibodies or immunoglobulins . Unlike alpha and beta globulins, which are produced in the liver, immunoglobulins are produced by specialized leukocytes known as plasma cells. Globulins make up approximately 38 percent of the total plasma protein volume, or 1.0–1.5 g/dL of blood.
The least abundant plasma protein is fibrinogen . Like albumin and the alpha and beta globulins, fibrinogen is produced by the liver. It is essential for blood clotting, a process described later in this chapter. Fibrinogen accounts for about 7 percent of the total plasma protein volume, or 0.2–0.45 g/dL of blood.

Other Plasma Solutes

In addition to proteins, plasma contains a wide variety of other substances. These include various electrolytes, such as sodium, potassium, and calcium ions; dissolved gases, such as oxygen, carbon dioxide, and nitrogen; various organic nutrients, such as vitamins, lipids, glucose, and amino acids; and metabolic wastes. All of these non-protein solutes combined contribute approximately 1 percent to the total volume of plasma.

This table lists the components of blood, the percentage of each component, their site of production, and their major functions.

Career Connection – Phlebotomy and Medical Lab Technology:

Medical or clinical laboratories employ a variety of individuals in technical positions:

Medical technologists (MT), also known as clinical laboratory technologists (CLT), typically hold a bachelor’s degree and certification from an accredited training program. They perform a wide variety of tests on various body fluids, including blood. The information they provide is essential to the primary care providers in determining a diagnosis and in monitoring the course of a disease and response to treatment.
Medical laboratory technicians (MLT) typically have an associate’s degree but may perform duties similar to those of an MT.
Medical laboratory assistants (MLA) spend the majority of their time processing samples and carrying out routine assignments within the lab. Clinical training is required, but a degree may not be essential to obtaining a position.

Chapter Review

Blood is a fluid connective tissue critical to the transportation of nutrients, gases, and wastes throughout the body; to defend the body against infection and other threats; and to the homeostatic regulation of pH, temperature, and other internal conditions. Blood is composed of formed elements—erythrocytes, leukocytes, and cell fragments called platelets—and a fluid extracellular matrix called plasma. More than 90 percent of plasma is water. The remainder is mostly plasma proteins—mainly albumin, globulins, and fibrinogen—and other dissolved solutes such as glucose, lipids, electrolytes, and dissolved gases. Because of the formed elements and the plasma proteins and other solutes, blood is more viscous than water. It is also slightly alkaline, and its temperature is slightly higher than normal body temperature.

Interactive Link Questions

There are values given for percent saturation, tension, and blood gas, and there are listings for different types of hemoglobin.

Review Questions

Critical thinking questions.

1. A patient’s hematocrit is 42 percent. Approximately what percentage of the patient’s blood is plasma?

2. Why would it be incorrect to refer to the formed elements as cells?

3. True or false: The buffy coat is the portion of a blood sample that is made up of its proteins.

Answers for Critical Thinking Questions

The patient’s blood is approximately 58 percent plasma (since the buffy coat is less than 1 percent).
The formed elements include erythrocytes and leukocytes, which are cells (although mature erythrocytes do not have a nucleus); however, the formed elements also include platelets, which are not true cells but cell fragments.
False. The buffy coat is the portion of blood that is made up of its leukocytes and platelets.

This work, Anatomy & Physiology, is adapted from Anatomy & Physiology by OpenStax , licensed under CC BY . This edition, with revised content and artwork, is licensed under CC BY-SA except where otherwise noted.

Images, from Anatomy & Physiology by OpenStax , are licensed under CC BY except where otherwise noted.

Access the original for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction .

Anatomy & Physiology Copyright © 2019 by Lindsay M. Biga, Staci Bronson, Sierra Dawson, Amy Harwell, Robin Hopkins, Joel Kaufmann, Mike LeMaster, Philip Matern, Katie Morrison-Graham, Kristen Oja, Devon Quick, Jon Runyeon, OSU OERU, and OpenStax is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License , except where otherwise noted.

Module 2: The Cardiovascular System: Blood

Blood typing, learning objectives.

By the end of this section, you will be able to:

Describe the two basic physiological consequences of transfusion of incompatible blood
Compare and contrast ABO and Rh blood groups
Identify which blood groups may be safely transfused into patients with different ABO types
Discuss the pathophysiology of hemolytic disease of the newborn

Blood transfusions in humans were risky procedures until the discovery of the major human blood groups by Karl Landsteiner, an Austrian biologist and physician, in 1900. Until that point, physicians did not understand that death sometimes followed blood transfusions, when the type of donor blood infused into the patient was incompatible with the patient’s own blood. Blood groups are determined by the presence or absence of specific marker molecules on the plasma membranes of erythrocytes. With their discovery, it became possible for the first time to match patient-donor blood types and prevent transfusion reactions and deaths.

Antigens, Antibodies, and Transfusion Reactions

Antigens are substances that the body does not recognize as belonging to the “self” and that therefore trigger a defensive response from the leukocytes of the immune system. (Seek more content for additional information on immunity.) Here, we will focus on the role of immunity in blood transfusion reactions. With RBCs in particular, you may see the antigens referred to as isoantigens or agglutinogens (surface antigens) and the antibodies referred to as isoantibodies or agglutinins. In this chapter, we will use the more common terms antigens and antibodies.

Antigens are generally large proteins, but may include other classes of organic molecules, including carbohydrates, lipids, and nucleic acids. Following an infusion of incompatible blood, erythrocytes with foreign antigens appear in the bloodstream and trigger an immune response. Proteins called antibodies (immunoglobulins), which are produced by certain B lymphocytes called plasma cells, attach to the antigens on the plasma membranes of the infused erythrocytes and cause them to adhere to one another.

Because the arms of the Y-shaped antibodies attach randomly to more than one nonself erythrocyte surface, they form clumps of erythrocytes. This process is called agglutination .
The clumps of erythrocytes block small blood vessels throughout the body, depriving tissues of oxygen and nutrients.
As the erythrocyte clumps are degraded, in a process called hemolysis , their hemoglobin is released into the bloodstream. This hemoglobin travels to the kidneys, which are responsible for filtration of the blood. However, the load of hemoglobin released can easily overwhelm the kidney’s capacity to clear it, and the patient can quickly develop kidney failure.

More than 50 antigens have been identified on erythrocyte membranes, but the most significant in terms of their potential harm to patients are classified in two groups: the ABO blood group and the Rh blood group.

The ABO Blood Group

Although the ABO blood group name consists of three letters, ABO blood typing designates the presence or absence of just two antigens, A and B. Both are glycoproteins. People whose erythrocytes have A antigens on their erythrocyte membrane surfaces are designated blood type A, and those whose erythrocytes have B antigens are blood type B. People can also have both A and B antigens on their erythrocytes, in which case they are blood type AB. People with neither A nor B antigens are designated blood type O. ABO blood types are genetically determined.

Normally the body must be exposed to a foreign antigen before an antibody can be produced. This is not the case for the ABO blood group. Individuals with type A blood—without any prior exposure to incompatible blood—have preformed antibodies to the B antigen circulating in their blood plasma. These antibodies, referred to as anti-B antibodies, will cause agglutination and hemolysis if they ever encounter erythrocytes with B antigens. Similarly, an individual with type B blood has pre-formed anti-A antibodies. Individuals with type AB blood, which has both antigens, do not have preformed antibodies to either of these. People with type O blood lack antigens A and B on their erythrocytes, but both anti-A and anti-B antibodies circulate in their blood plasma.

Rh Blood Groups

The Rh blood group is classified according to the presence or absence of a second erythrocyte antigen identified as Rh. (It was first discovered in a type of primate known as a rhesus macaque, which is often used in research, because its blood is similar to that of humans.) Although dozens of Rh antigens have been identified, only one, designated D, is clinically important. Those who have the Rh D antigen present on their erythrocytes—about 85 percent of Americans—are described as Rh positive (Rh + ) and those who lack it are Rh negative (Rh − ). Note that the Rh group is distinct from the ABO group, so any individual, no matter their ABO blood type, may have or lack this Rh antigen. When identifying a patient’s blood type, the Rh group is designated by adding the word positive or negative to the ABO type. For example, A positive (A + ) means ABO group A blood with the Rh antigen present, and AB negative (AB − ) means ABO group AB blood without the Rh antigen.

The following chart summarizes the distribution of the ABO and Rh blood types within the United States.

Table 1. Summary of ABO and Rh Blood Types within the United States
Blood Type	African-Americans	Asian-Americans	Caucasian-Americans	Latino/Latina-Americans
A	24	27	33	29
A	2	0.5	7	2
B	18	25	9	9
B	1	0.4	2	1
AB	4	7	3	2
AB	0.3	0.1	1	0.2
O	47	39	37	53
O	4	1	8	4

In contrast to the ABO group antibodies, which are preformed, antibodies to the Rh antigen are produced only in Rh − individuals after exposure to the antigen. This process, called sensitization, occurs following a transfusion with Rh-incompatible blood or, more commonly, with the birth of an Rh + baby to an Rh − mother. Problems are rare in a first pregnancy, since the baby’s Rh + cells rarely cross the placenta (the organ of gas and nutrient exchange between the baby and the mother). However, during or immediately after birth, the Rh − mother can be exposed to the baby’s Rh + cells (Figure 1). Research has shown that this occurs in about 13−14 percent of such pregnancies. After exposure, the mother’s immune system begins to generate anti-Rh antibodies. If the mother should then conceive another Rh + baby, the Rh antibodies she has produced can cross the placenta into the fetal bloodstream and destroy the fetal RBCs. This condition, known as hemolytic disease of the newborn (HDN) or erythroblastosis fetalis, may cause anemia in mild cases, but the agglutination and hemolysis can be so severe that without treatment the fetus may die in the womb or shortly after birth.

This figure shows an umbilical artery and vein passing through the placenta on the top left. The top right panel shows the first exposure to Rh+ antibodies in the mother. The bottom right panel shows the response when the second exposure in the form of another fetus takes place. Textboxes detail the steps in each process.

Figure 1. The first exposure of an Rh − mother to Rh + erythrocytes during pregnancy induces sensitization. Anti-Rh antibodies begin to circulate in the mother’s bloodstream. A second exposure occurs with a subsequent pregnancy with an Rh + fetus in the uterus. Maternal anti-Rh antibodies may cross the placenta and enter the fetal bloodstream, causing agglutination and hemolysis of fetal erythrocytes.

A drug known as RhoGAM, short for Rh immune globulin, can temporarily prevent the development of Rh antibodies in the Rh − mother, thereby averting this potentially serious disease for the fetus. RhoGAM antibodies destroy any fetal Rh + erythrocytes that may cross the placental barrier. RhoGAM is normally administered to Rh − mothers during weeks 26−28 of pregnancy and within 72 hours following birth. It has proven remarkably effective in decreasing the incidence of HDN. Earlier we noted that the incidence of HDN in an Rh + subsequent pregnancy to an Rh − mother is about 13–14 percent without preventive treatment. Since the introduction of RhoGAM in 1968, the incidence has dropped to about 0.1 percent in the United States.

Determining ABO Blood Types

Clinicians are able to determine a patient’s blood type quickly and easily using commercially prepared antibodies. An unknown blood sample is allocated into separate wells. Into one well a small amount of anti-A antibody is added, and to another a small amount of anti-B antibody. If the antigen is present, the antibodies will cause visible agglutination of the cells (Figure 2). The blood should also be tested for Rh antibodies.

This figure shows three different red blood cells with different blood types.

Figure 2. This sample of a commercially produced “bedside” card enables quick typing of both a recipient’s and donor’s blood before transfusion. The card contains three reaction sites or wells. One is coated with an anti-A antibody, one with an anti-B antibody, and one with an anti-D antibody (tests for the presence of Rh factor D). Mixing a drop of blood and saline into each well enables the blood to interact with a preparation of type-specific antibodies, also called anti-seras. Agglutination of RBCs in a given site indicates a positive identification of the blood antigens, in this case A and Rh antigens for blood type A + . For the purpose of transfusion, the donor’s and recipient’s blood types must match.

ABO Transfusion Protocols

To avoid transfusion reactions, it is best to transfuse only matching blood types; that is, a type B + recipient should ideally receive blood only from a type B + donor and so on. That said, in emergency situations, when acute hemorrhage threatens the patient’s life, there may not be time for cross matching to identify blood type. In these cases, blood from a universal donor —an individual with type O − blood—may be transfused. Recall that type O erythrocytes do not display A or B antigens. Thus, anti-A or anti-B antibodies that might be circulating in the patient’s blood plasma will not encounter any erythrocyte surface antigens on the donated blood and therefore will not be provoked into a response. One problem with this designation of universal donor is if the O − individual had prior exposure to Rh antigen, Rh antibodies may be present in the donated blood. Also, introducing type O blood into an individual with type A, B, or AB blood will nevertheless introduce antibodies against both A and B antigens, as these are always circulating in the type O blood plasma. This may cause problems for the recipient, but because the volume of blood transfused is much lower than the volume of the patient’s own blood, the adverse effects of the relatively few infused plasma antibodies are typically limited. Rh factor also plays a role. If Rh − individuals receiving blood have had prior exposure to Rh antigen, antibodies for this antigen may be present in the blood and trigger agglutination to some degree. Although it is always preferable to cross match a patient’s blood before transfusing, in a true life-threatening emergency situation, this is not always possible, and these procedures may be implemented.

A patient with blood type AB + is known as the universal recipient . This patient can theoretically receive any type of blood, because the patient’s own blood—having both A and B antigens on the erythrocyte surface—does not produce anti-A or anti-B antibodies. In addition, an Rh + patient can receive both Rh + and Rh − blood. However, keep in mind that the donor’s blood will contain circulating antibodies, again with possible negative implications. Figure 3 summarizes the blood types and compatibilities.

At the scene of multiple-vehicle accidents, military engagements, and natural or human-caused disasters, many victims may suffer simultaneously from acute hemorrhage, yet type O blood may not be immediately available. In these circumstances, medics may at least try to replace some of the volume of blood that has been lost. This is done by intravenous administration of a saline solution that provides fluids and electrolytes in proportions equivalent to those of normal blood plasma. Research is ongoing to develop a safe and effective artificial blood that would carry out the oxygen-carrying function of blood without the RBCs, enabling transfusions in the field without concern for incompatibility. These blood substitutes normally contain hemoglobin- as well as perfluorocarbon-based oxygen carriers.

This table shows the different blood types, the antibodies in plasma, the antigens in the red blood cell, and the blood compatible blood types in an emergency.

Figure 3. This chart summarizes the characteristics of the blood types in the ABO blood group. See the text for more on the concept of a universal donor or recipient.

Chapter Review

Antigens are nonself molecules, usually large proteins, which provoke an immune response. In transfusion reactions, antibodies attach to antigens on the surfaces of erythrocytes and cause agglutination and hemolysis. ABO blood group antigens are designated A and B. People with type A blood have A antigens on their erythrocytes, whereas those with type B blood have B antigens. Those with AB blood have both A and B antigens, and those with type O blood have neither A nor B antigens. The blood plasma contains preformed antibodies against the antigens not present on a person’s erythrocytes.

A second group of blood antigens is the Rh group, the most important of which is Rh D. People with Rh − blood do not have this antigen on their erythrocytes, whereas those who are Rh + do. About 85 percent of Americans are Rh + . When a woman who is Rh − becomes pregnant with an Rh + fetus, her body may begin to produce anti-Rh antibodies. If she subsequently becomes pregnant with a second Rh + fetus and is not treated preventively with RhoGAM, the fetus will be at risk for an antigen-antibody reaction, including agglutination and hemolysis. This is known as hemolytic disease of the newborn.

Cross matching to determine blood type is necessary before transfusing blood, unless the patient is experiencing hemorrhage that is an immediate threat to life, in which case type O − blood may be transfused.

Critical Thinking Questions

Following a motor vehicle accident, a patient is rushed to the emergency department with multiple traumatic injuries, causing severe bleeding. The patient’s condition is critical, and there is no time for determining his blood type. What type of blood is transfused, and why?
In preparation for a scheduled surgery, a patient visits the hospital lab for a blood draw. The technician collects a blood sample and performs a test to determine its type. She places a sample of the patient’s blood in two wells. To the first well she adds anti-A antibody. To the second she adds anti-B antibody. Both samples visibly agglutinate. Has the technician made an error, or is this a normal response? If normal, what blood type does this indicate?
In emergency situations, blood type O − will be infused until cross matching can be done. Blood type O − is called the universal donor blood because the erythrocytes have neither A nor B antigens on their surface, and the Rh factor is negative.
The lab technician has not made an error. Blood type AB has both A and B surface antigens, and neither anti-A nor anti-B antibodies circulating in the plasma. When anti-A antibodies (added to the first well) contact A antigens on AB erythrocytes, they will cause agglutination. Similarly, when anti-B antibodies contact B antigens on AB erythrocytes, they will cause agglutination.

ABO blood group: blood-type classification based on the presence or absence of A and B glycoproteins on the erythrocyte membrane surface

agglutination: clustering of cells into masses linked by antibodies

cross matching: blood test for identification of blood type using antibodies and small samples of blood

hemolysis: destruction (lysis) of erythrocytes and the release of their hemoglobin into circulation

hemolytic disease of the newborn (HDN): (also, erythroblastosis fetalis) disorder causing agglutination and hemolysis in an Rh + fetus or newborn of an Rh − mother

Rh blood group: blood-type classification based on the presence or absence of the antigen Rh on the erythrocyte membrane surface

universal donor: individual with type O − blood

universal recipient: individual with type AB + blood

American Red Cross (US). Blood types [Internet]. c2013 [cited 2013 Apr 3]. Available from: http://www.redcrossblood.org/learn-about-blood/blood-types 2013.

Anatomy & Physiology. Provided by : OpenStax CNX. Located at : http://cnx.org/contents/[email protected] . License : CC BY: Attribution . License Terms : Download for free at http://cnx.org/contents/[email protected]

Eligibility Requirements

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Requirements by Donation Type

To ensure the safety of both patients and donors, these are some of the requirements donors must meet to be eligible to donate blood based on their donation type. To explore a list of eligibility information, Search by Keyword or Browse All .

Now, more people can donate blood . Learn about recent eligibility changes for those who spent time in Europe, and the elimination of questions based on gender and sexual orientation in our Eligibility FAQs . More information also on our LGBTQ+ Donors page .

Whole Blood Donation

Donation frequency: Every 56 days, up to 6 times a year*
You must be in good health and feeling well**
You must be at least 16 years old in most states
You must weigh at least 110 lbs

See additional requirements for students >>

Learn more about donating whole blood >>

Power Red Donation

Donation frequency: Every 112 days, up to 3 times/year*
Male donors + must be at least 17 years old in most states, at least 5'1" tall and weigh at least 130 lbs
Female donors + must be at least 19 years old, at least 5'3" tall and weigh at least 150 lbs

See additional requirements for student donors >>

Learn more about donating Power Red >>

Platelet Donation

Donation frequency: Every 7 days, up to 24 times/year*
You must be at least 17 years old in most states

Learn more about donating platelets >>

AB Elite Plasma Donation

Donation frequency: Every 28 days, up to 13 times/year*
You must have type AB blood
You must be at least 17 years old

Learn more about donating AB Plasma >>

Common Reasons People Can't Donate

If you don’t feel well on the day of your donation, please call to cancel. We’ll be happy to see you 24 hours after your symptoms pass.

Most medications will not disqualify you from being able to donate blood, but may require a waiting period after your final dose.

If you were unable to donate due to low iron, you may still be able to donate in the future. The Red Cross recommends taking steps to help increase your iron level.

You may be deferred from donating blood or platelets if you have lived in or traveled to a malaria-risk country in the past three years.

Other Ways to Help

This list is not complete. Specially trained technical staff are available at each blood collection center and details of each donor’s health and activities are discussed in a confidential setting prior to blood donation. The majority of donor eligibility rules are specified by the Food and Drug Administration for every collection center in the country. Other rules are determined by the medical professionals at specific blood centers, or with other regulatory bodies. Therefore, rules may differ between programs. Donor eligibility rules are intended to protect the health and safety of the donor as well as the patient who will receive the transfusion. The criteria listed are provided as guidelines to assist you in determining whether you may be eligible to be a blood donor. The final determination of eligibility is made at the time of donation. The guidelines listed below were last revised on 08/01/17. There may have been some changes to these criteria since the last revision date. The most up-to-date eligibility information can be obtained by contacting the Donor Client Support Center at 1-866-236-3276 .

*The number of allowable donations per year may be lower due to red cell and plasma loss limit guidelines. Final eligibility will be determined by the American Red Cross at the time of donation.

** Healthy means that you feel well and can perform normal activities. If you have a chronic condition such as diabetes, healthy also means that you are being treated and the condition is under control. If you are not feeling well on the day of your donation, please contact us to reschedule.

+ Please note higher requirements may apply in certain cases. Check with your donor center to confirm.

Basic Genetics

Genes and Blood Type

Blood is a complex, living tissue that contains many cell types and proteins. A transporter, regulator, and defender, blood courses through the body carrying out many important functions.

Blood Types

Distinct molecules called agglutinogens (a type of antigen) are attached to the surface of red blood cells. There are two different types of agglutinogens, type "A" and type "B". Each type has different properties. The ABO blood type classification system uses the presence or absence of these molecules to categorize blood into four types.

Another level of specificity is added to blood type by examining the presence or absence of the Rh protein. Each blood type is either positive "+" (has the Rh protein) or negative "-" (no Rh protein). For example, a person whose blood type is "A positive" (A +), has both type A and Rh proteins on the surface of their red blood cells.

Type A blood cells are covered with A agglutinogens, type B have B agglutinogens, type AB have both A and B, and type O blood have none.

Blood Type Is Determined Genetically

The A and B antigen molecules on the surface of red blood cells are made by two different enzymes. These two enzymes are encoded by different versions, or alleles, of the same gene.

The A allele codes for an enzyme that makes the A antigen, and the B allele codes for an enzyme that makes the B antigen. A third version of this gene, the O allele, codes for a protein that is not functional; it makes no surface molecules at all.

Everyone inherits two alleles of the gene, one from each parent. The combination of your two alleles determines your blood type.

The table on the left shows all of the possible combinations of blood type alleles. The blood type for each allele combination is shown on the right. For example, if you inherit a B allele from your father and an A allele from your mother, your blood type will be AB.

When Blood Types Mix

Blood plasma is packed with proteins called antibodies. The body produces a wide variety of antibodies that will recognize and attack foreign molecules that may enter from the outside world. A person's plasma does not contain any antibodies that will bind to molecules that are part of his or her own body.

When conducting a blood transfusion, it is important to carefully match the donor and recipient blood types. If the donor blood cells have surface molecules that are different from those of the recipient, antibodies in the recipient's blood recognize the donor blood as foreign. This triggers an immune response resulting in blood clotting. If the donor blood cells have surface molecules that are the same as those of the recipient, the recipient's body will not see them as foreign and will not mount an immune response.

There are two special blood types when it comes to blood transfusions. People with type O blood are universal donors because there are no molecules on the surface of the red blood cells that can trigger an immune response. People with type AB blood are universal recipients because they do not have any antibodies that will recognize type A or B surface molecules.

Note: Blood cells are covered with a variety of surface molecules. For simplicity, only type A and B surface molecules are shown here.

Funding provided by grant 51006109 from the Howard Hughes Medical Institute, Precollege Science Education Initiative for Biomedical Research.

Assignment on Blood Hematology

Introduction

Blood is a specialized fluid connective tissue in which there are liquid intercellular substances (plasma) and formed elements (RBC, WBC, Platelet) suspended in the plasma which circulates in closed system of blood vessels. it is red thick and slightly alkaline 1

The normal total circulating blood volume is about 8% of the body weight (5600 ml in a 70 kg man). About 55% of this volume is plasma and 45% is cellular element that is composed of WBC, RBC, and Platelet that suspended in the plasma.

Structurally the simplest cell in the body, volumes have been written about the lower red blood cell. The basic function of the RBC is the creation and maintenance of an environment salutary to the physical integrity and functionality of hemoglobin. In the normal state, erythrocytes are produced only in the skeleton (in adults only in the axial skeleton), but in pathologic states (especially myelofibrosis, which will be covered subsequently) almost any organ can become the site of erythropoiesis. Numerous substances are necessary for creation of erythrocytes, including metals (iron, cobalt, manganese), vitamins (B 12 , B 6 , C, E, foliate, riboflavin, pantothenic acid, thiamin), and amino acids. Regulatory substances necessary for normal erythropoiesis include erythropoietin, thyroid hormones, and androgens. Erythrocytes progress from blast precursors in the marrow over a period of five days. Then they are released into the blood as reticulocytes, distinguishable from regular erythrocytes only with special supravital

stains. The reticulocyte changes to an erythrocyte in one day and circulates for 120 days before being destroyed in the reticuloendothelial system ]

Also referred to as just “RBC,” this simply involves counting the number of RBC per unit volume of whole blood. Manual methods using the hated hemocytometer have been universally replaced by automated counting. The major source of error in the RBC count is an artificially reduced result that occurs in some conditions where RBC stick together in the sample tube, with two or more cells being counted as one. The result of the test is expressed as number of cells per unit volume, specifically cells/µL. A typical lab’s normal range is 4.2 – 5.4 x 10 6 /µL for females; for adult males it is 4.7 – 6.1 x 10 6 /µL. 3 Hemoglobin, also spelled haemoglobin and abbreviated Hb, is the iron-containing oxygen-transport metalloprotein in the red blood cells of the blood in vertebrates and other animals. In mammals the protein makes up about 97% of the red cell’s dry content, and around 35% of the total content (including water). Hemoglobin transports oxygen from the lungs or gills to the rest of the body, such as to the muscles, where it releases its load of oxygen. Hemoglobin also has a variety of other gas-transport and effect-modulation duties, which vary from species to species, and may be quite diverse in invertebrates.

The name hemoglobin is the concatenation of heme and globin, reflecting the fact that each subunit of hemoglobin is a globular protein with an embedded heme (or haem) group; each heme group contains an iron atom, and this is responsible for the binding of oxygen. The most common type of hemoglobin in mammals contains four such subunits, each with one heme group. In humans, each heme group is able to bind one oxygen molecule, and thus, one hemoglobin molecule can bind four oxygen molecules.

The normal range for hemoglobin is highly age- and sex-dependent, with men having higher values than women, and adults having higher values than children (except neonates, which have the highest values of all). For a typical clinical lab, the young adult female normal range is 12 – 16 g/dl; for adult males it is 14 – 18 g/dl.

Hemoglobin (Hb) is synthesized in a complex series of steps. The heme portion is synthesized in a series of steps which occur in the mitochondria and the cytosol of the immature red blood cell, while the globin protein portions of the molecule are synthesized by ribosomes in the cytosol [3] . Production of Hb continues in the cell throughout its early development from the proerythroblast to the reticulocyte in the bone marrow. At this point, the nucleus is lost in mammalian red blood cells, but not in birds and many other species. Even after the loss of the nucleus in mammals, residual ribosomal RNA allows further synthesis of Hb until the reticulocyte loses its RNA soon after entering the vasculature (this hemoglobin-synthetic RNA in fact gives the reticulocyte its reticulated appearance and name).

Decrease of hemoglobin, with or without an absolute decrease of red blood cells, leads to symptoms of anemia. Anemia has many different causes, although iron deficiency and its resultant iron deficiency anemia are the most common causes in the Western world. As absence of iron decreases heme synthesis, red blood cells in iron deficiency anemia are hypochromic (lacking the red hemoglobin pigment) and microcytic (smaller than normal). Other anemias are rarer. In hemolysis (accelerated breakdown of red blood cells), associated jaundice is caused by the hemoglobin metabolite bilirubin, and the circulating hemoglobin can cause renal failure Anemia is present when the hemoglobin level in the blood is below the lower extreme of normal range for the age and sex of the individual. The lower limit of normality is reduced during pregnancy.

Anemia can be caused by many things, but the three main bodily mechanism that produces it are: excessive destruction of RBC, blood loss, inadequate production of RBCs.

Clinical manifestations of anemia are symptoms like fatigue, tierdness, effort intolerance, effort dyspnoea, and palpitaions

Signs are pallor, high cardiac output state, and congestive cardiac failure.

Anemia is usually classified according to etiology, path physiology & morphology

MORPHOLOGIC CLASSIFICATION of Anaemia

MCV > 100 MCH and MCHC normal
MCV > normal MCH and MCHC normal
MCV < 80 MCH and MCHC normal
MCV < 80 MCH and MCHC decreased

Iron deficiency – absence of iron, chronic disease – iron unavailable, thalassemia – inability to produce globin chains & sideroblastic anemia- inability to produce heme

Iron deficiency anemia is the most common type of anemia, and the most common cause of anemia. Iron deficiency anemia occurs when the dietary intake or absorption of iron is

insufficient, and hemoglobin, which contains iron, cannot be formed. The principal cause of iron deficiency anemia in premenopausal women is blood lost during menses.

The hereditary disorder of hemoglobin may be classified two broad groups, the hemoglobinopathies and the thalassaemias.The hemoglobinopathies are characterized by the production of structurally defective hemoglobin due to abnormallities in the formation of the globin moiety of the moelcule.the thallasaemia are characterized by a reduced rate of production of normal hemoglobin due to absent or decreased synthesis of 1 or more types of globin polypeptide chains. The thalassaemias are wide spread with maximam prevalence arround the Mediterranean littoral and in south East Asia

Risk factors are conditions or behaviors that increase chances of developing diseases, Iron deficiency is more frequent in women who smoke, eat a diet low in iron and have heavy periods In adults the most common cause is losing blood faster than the body can replace it. A lack of iron in the diet is common in vegans and vegetarians because the main dietary source is red meat, babies can develop iron deficiency, especially if they are premature. Storing iron is not usually completed until the final stages of pregnancy, the body needs more iron when a large amount of cell divisions occur, such as in pregnancy and during periods of rapid childhood growth, loss of blood through heavy menstruation can deplete iron stores, diseases of the small intestine such as gluten intolerance (coeliac disease) and Crohn’s disease (inflammation of the intestine) can reduce its ability to absorb iron, gender discrimination, illiteracy, poor economic status.

A combination of these factors possibly contributes to the low level of awareness, treatment and control of anaemia in our country. This is a community study with descriptive nature. This was cross-sectional in pattern of time and approach to the study subjects. For this study standards were set according to the World Health Organization set criteria for research. 13

Following measures should be taken to maintain the normal level of Hb in young adults: Eat a varied, well-balanced diet that contains foods from all the food groups (protein,

carbohydrate, fat, fruit, and vegetables). Good sources of iron include liver, beef, whole meal bread, cereals, eggs and dried fruit. If you often get heavy periods, it’s a good idea to seek medical advice because you may be at risk of anaemia. If you are pregnant or planning to become pregnant, talk to your doctor about iron supplements. Hence public education to overcome such problem and promote healthy behaviors is essential and should be directed towards the individual and the community, and should start early in childhood.

Bangladesh, on the northern coast of the Bay of Bengal, is surrounded by India, with a small common border with Myanmar in the southeast. Bangladesh is a developing country of the world. Area is about 56,977 square miles and population 124 million. According to statistical year book 2001, gross national income per capita is US $ 375.Along with high birth rate and lower literacy level most of the people lies below the poverty line. So many of our young adult suffering from nutritional deficiency. Such as anemia, PEM etc. On the background of Bangladesh, the cause of nutritional deficiency mainly are poverty, lack of proper knowledge, high birth rate, unhealthy mother give birth unhealthy baby.

The normal Hb level of young adult range is Female 12-16 gm/dl & Male 14-18 gm/dl. Most of our young adults in Bangladesh are anaemic due to their Hb level in the blood is below normal range. Anemia one of the more common blood disorder, occurs when the level of healthy red blood cell in the body becomes too low. This can lead to Health problem because RBCs contain Hb, which carries Oxygen to the body’s tissues. The body needs iron, vitamin B12 and folic acid to produce more red blood cells. If there is a lack of one or more of these nutrients, anemia will develop. Iron deficiency anemia is the most common type of anemia. Anemia can cause a variety of complications, Including fatigue and stress on bodily organs. A lack of iron in the diet is common in vegans and vegetarians because the main dietary source is red meat. Babies can develop iron deficiency, especially if they are premature. Storing iron is not usually completed until the final stages of pregnancy. The body needs more iron when a large amount of cell divisions occur, such as in pregnancy and during periods of rapid childhood growth. Loss of blood through heavy menstruation can deplete iron stores. The young generation is the future of our country. They are the prime mover of development. So they should have awakened about their health & nutrition and also take precaution such as:

Iron tablet will rapidly reverse anemia, so long as any underlying cause of blood loss has been treated. The tablets can irritate the stomach and should be taken after food to prevent this. There may be a need for intramuscular iron injections to be given instead of tablets, but this is far less common. So many of them are severely malnourished and unhealthy. These conditions increase their malleability to disease and reduce child’s chance of proper nutrition and health. Good nutrition is the cornerstone for survival, health and development for current and succeeding generations. Well-nourished children perform better in school, grow into healthy adults and in turn give their children a better start in life. Well-nourished women face fewer risks during pregnancy and childbirth, and their children set off on firmer under nutrition is implicated in more than half of all child death worldwide. Under nourished children have lowered resistance to infection; they are more likely to die from common childhood ailments like diarrhoeal diseases and respiratory infections, and for those who survive, frequent illness saps their nutritional status, locking them into a vicious cycle of recurring sickness and faltering growth. Their plight is largely invisible: three quarters of the children who die from causes related to malnutrition were only mildly or moderately undernourished, showing no outward sign of their vulnerability.evelopmental paths, both physically and mentally. Malnutrition is a complex condition that can involve multiple, overlapping deficiencies of protein, energy and micronutrients — so called because they are nutrients needed by the body in only tiny amounts. A child becomes malnourished because of illness in combination with inadequate food intake. Insufficient access to food, poor health services, the lack of safe water and sanitation, and inadequate child and maternal care. Inadequate care for children and women is an underlying cause of malnutrition only recently recognized in all its harmful ramifications. Good hygiene in and around the home and in handling food reduces the risk of illness. Care also includes all interaction between parent and child that helps children develop emotionally as well as physically. Several studies have found that

malnourished children who were stimulated verbally and cognitively had higher growth rates than those who were not. UNICEF supplied a total of 2.7 billion iron/foliate tablets to 122 countries between 1993 and 1996 for distribution among pregnant women to help reduce iron deficiency anaemia and foliate deficiency. Wheat flour is being fortified with iron in a number of countries in Latin America and the Middle East. Nutrition promoters in Bangladesh are working in 1,000 community centers to help support breastfeeding and better caring practices for women and children. Breastfeeding is the foundation of good nutrition for infants, and inadequate breastfeeding can jeopardize infants’ health and for their normal growth and development of body. In Bangladesh, most of the people suffer from microcytic hypocromic anemia. This may be due to the presence of sub clinical iron deficiency. Both clinical and sub clinical iron deficiency constitute one of the most frequently encountered nutritional anemia and the prevalence of iron responsive microcytic hypocromic anemia varies from 9-70% in different population group. The incidence being higher in the less developed countries compared to the nation of the world. In the United States and Canada the prevalence of microcytic hypocromic anemia

Was reported to the range from 2.3%-27%.There are several causes of iron deficiency including many parasitic disease and other infection, consumption of highly refined food, Use of aluminum and steel cookware rather than iron utensils, lower intake of iron rich food, particularly vegetables and gastrointestinal disorder loading to impaired iron absorption. Hemoglobin level of the people depends on their socio economic condition, literacy level and awareness. There is a direct proportional relationship between higher education level of people and hemoglobin level of them. So it can be suggested that hemoglobin level can be improved by increasing literacy rate and awareness of the people, consciousness about their personal hygiene, and food habit may play an important role in this regard.

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COMMENTS

18.1 An Overview of Blood
Recall that blood is a connective tissue. Like all connective tissues, it is made up of cellular elements and an extracellular matrix. The cellular elements—referred to as the formed elements —include red blood cells (RBCs), white blood cells (WBCs), and cell fragments called platelets.The extracellular matrix, called plasma, makes blood unique among connective tissues because it is fluid.
Blood Anatomy and Physiology: Study Guide for Nurses
Blood is heavier than water and about five times thicker, or more viscous, largely because of its formed elements. pH. Blood is slightly alkaline, with a pH between 7.35 and 7.45. Temperature. Its temperature (38 degrees Celsius, or 100.4 degrees Fahrenhei t) is always slightly higher than body temperature.
Structure and Function of Blood
Red Blood Cells. Red blood cells, or erythrocytes (erythro- = "red"; -cyte = "cell"), are specialized cells that circulate through the body delivering oxygen to cells; they are formed from stem cells in the bone marrow. In mammals, red blood cells are small biconcave cells that at maturity do not contain a nucleus or mitochondria and are only 7-8 µm in size.
Blood assignment Flashcards
Blood assignment. Flashcards; Learn; Test; Match; Q-Chat; Get a hint. Plasma. liquid portion of blood. 1 / 10. 1 / 10. Flashcards; Learn; Test; Match; Q-Chat; Created by. Tcarter0294. Share. ... iron-containing protein in red blood cells that carries oxygen for delivery to cells. Leukemia. cancer of white blood cells. hematocrit. the percentage ...
PDF Biology 212: Anatomy and Physiology II Lab #2: BLOOD/HEMATOLOGY
like, or you can use one of the Histology textbooks in the lab.Part 1: Erythrocytes: By far, erythrocytes a. e the most numerous of the cells you will see on a blood smear. From your Bio 211 experience, you will remember that erythrocytes are smal. (7.5 microns in diameter), round, and have an indented center.
Blood
blood, fluid that transports oxygen and nutrients to the cells and carries away carbon dioxide and other waste products. Technically, blood is a transport liquid pumped by the heart (or an equivalent structure) to all parts of the body, after which it is returned to the heart to repeat the process. Blood is both a tissue and a fluid.
PDF CHAPTER 7
Step 1: Have students work as individuals or in pairs. Assign each student one of the following topics: blood or plasma. Step 2: Tell students they are to assume the role of a Human Body Resources Manager. It is their job to hire blood and plasma for their bodies.
Blood Assignment Flashcards
Plasma is the liquid portion of blood. Serum is the extracellular portion of blood and is a clotting factor. Serum is obtained after blood is allowed to clot and plasma is obtained after treating blood with an anticoagulation compound. What hormone is responsible for erythrocyte production, where is made, what stimulates its production?
A&P 2 Lab
Male: 42-52%. Female: 37-47%. Anemia. deficiency in the oxygen carrying capacity of the blood - decrease in RBCs and/or hemoglobin. Polcythemia. an excessive or abnormal increase in the number of red blood cells. Blood type is determined by the presence or absence of. antigens. A blood has _____ antigens.
Composition of Blood and its Functions
Blood is a fluid connective tissue which comprises RBC, WBC, platelets and plasma. The main function of blood is to deliver oxygen and nutrients to various cells and tissues of the body. 2. State the types of blood cells found in human blood. Blood cells are classified into the following types:
18.1 Functions of Blood
Recall that blood is a connective tissue. Like all connective tissues, it is made up of cellular elements and an extracellular matrix. The cellular elements—referred to as the formed elements—include red blood cells (RBCs), white blood cells (WBCs), and cell fragments called platelets.The extracellular matrix, called plasma, makes blood unique among connective tissues because it is fluid.
Blood Typing
When identifying a patient's blood type, the Rh group is designated by adding the word positive or negative to the ABO type. For example, A positive (A +) means ABO group A blood with the Rh antigen present, and AB negative (AB −) means ABO group AB blood without the Rh antigen. The following chart summarizes the distribution of the ABO and ...
Eligibility Requirements
Donation frequency: Every 112 days, up to 3 times/year*. You must be in good health and feeling well**. Male donors+ must be at least 17 years old in most states, at least 5'1" tall and weigh at least 130 lbs. Female donors+ must be at least 19 years old, at least 5'3" tall and weigh at least 150 lbs. See additional requirements for student ...
Genes and Blood Type
Blood Type Is Determined Genetically. The A and B antigen molecules on the surface of red blood cells are made by two different enzymes. These two enzymes are encoded by different versions, or alleles, of the same gene. The A allele codes for an enzyme that makes the A antigen, and the B allele codes for an enzyme that makes the B antigen.
Unit 20: Learning Aim, A: Composition of Human Blood
Blood type O does not have any antigens on the RBC; however, the blood plasma has Anti-A and Anti-B antibodies, including the other two blood types which have antibodies against the other antigen. Rh typing also looks for an antigen on the red blood cells, if it is present then the individual is Rh positive, if not they are negative.
Assignment on Blood Hematology
Assignment. Introduction. Blood is a specialized fluid connective tissue in which there are liquid intercellular substances (plasma) and formed elements (RBC, WBC, Platelet) suspended in the plasma which circulates in closed system of blood vessels. it is red thick and slightly alkaline 1. The normal total circulating blood volume is about 8% ...
NCLEX: Prioritizing Flashcards
4. A client with a white blood cell count of 14,000 mm3 (14.0 × 109/L) and a temperature of 101°F (38.4°C) Rationale: The nurse should plan to care for the client who has an elevated white blood cell count and a fever first because this client's needs are the priority. The client who is ambulatory with steady gait and the client scheduled for physical therapy for a crutch-walking session do ...
Prioritization Practice Test Flashcards
Study with Quizlet and memorize flashcards containing terms like The nurse just finished receiving the client assignment for the day. Which client would the nurse see first? The client requesting to speak to the charge nurse The client slumped down in bed with an oxygen saturation of 94% The client requesting medications before breakfast The client who is agitated following surgery, The nurse ...

18.1 An Overview of Blood

Functions of Blood

Transportation

Maintenance of Homeostasis

Composition of Blood

Characteristics of Blood

Blood Plasma

Interactive Link

Plasma Proteins

Other Plasma Solutes

Career Connection

Blood Anatomy and Physiology

Table of Contents

Components of Blood

Formed Elements

Blood Groups and Transfusions

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Blood components

Types of Blood Cells

Red blood cells (Erythrocytes)

White blood cells (Leucocytes)

Types of White Blood Cells

Granulocytes

Eosinophils

Neutrophils

Lymphocytes

Platelets (Thrombocytes)

Components Of Blood

Red Blood Cells (RBC)

White Blood Cells (WBC)

Blood Vessels

Recommended Video:

Types of Blood Vessels

Layers of Blood Vessels

Functions of Blood

Fluid Connective Tissue

Transports Hormones and Nutrients

Homeostasis

Blood Clotting at Site of Injury

Transport of waste to the Kidney and Liver

Protection of the body against pathogens

Frequently Asked Questions

3. State the different types of white blood cells found in the blood.

4. What are granulocytes?

5. What are agranulocytes?

6. Name the various components of blood.

7. What are the various types of blood vessels present in our body?

8. What are sinusoids?

9. Name the various layers of blood vessels.

10. Name the major functions of blood.

11. What gives blood its red colour?

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18.1 Functions of Blood

Functions of Blood

Transportation

Maintenance of Homeostasis

Composition of Blood

Characteristics of Blood

Blood Plasma

External Website

Plasma Proteins

Other Plasma Solutes

Career Connection – Phlebotomy and Medical Lab Technology:

Chapter Review

Interactive Link Questions

Review Questions

Module 2: The Cardiovascular System: Blood

Antigens, Antibodies, and Transfusion Reactions

The ABO Blood Group

Rh Blood Groups

Determining ABO Blood Types

ABO Transfusion Protocols

Chapter Review

Critical Thinking Questions

Eligibility Requirements

Requirements by Donation Type

Whole Blood Donation