Chapter 18: BLOOD

Discuss the most common malignancies involving leukocytes.

Leukemia is a cancer involving an abundance of leukocytes. It may involve only one specific type of leukocyte from either the myeloid line (myelocytic leukemia) or the lymphoid line (lymphocytic leukemia). In chronic leukemia, mature leukocytes accumulate and fail to die. In acute leukemia, there is an overproduction of young, immature leukocytes. In both conditions the cells do not function properly. Lymphoma is a form of cancer in which masses of malignant T and/or B lymphocytes collect in lymph nodes, the spleen, the liver, and other tissues. As in leukemia, the malignant leukocytes do not function properly, and the patient is vulnerable to infection. Some forms of lymphoma tend to progress slowly and respond well to treatment. Others tend to progress quickly and require aggressive treatment, without which they are rapidly fatal.

Name the fluid component of blood and the three major types of formed elements, and identify their relative proportions in a blood sample.

hematocrit measures the percentage of RBCs clinically known as eryhtocytes in a blood sample. leukocytes and platelets and thrombocytes are referred to as the buffy coat and it is less than 1% of the blood sample. 45% is erythrocytes, hematocrit is 36-50%

Discuss the role of hemopoietic growth factors in promoting the production of formed elements.

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Explain how the extrinsic and intrinsic coagulation pathways lead to the common pathway, and the coagulation factors involved in each.

Both the intrinsic and extrinsic pathways lead to the common pathway, in which fibrin is produced to seal off the vessel. Once factor X has been activated by either the intrinsic or extrinsic pathway, the enzyme prothrombinase converts factor II, the inactive enzyme prothrombin, into the active enzyme thrombin. Then, thrombin converts factor I, the soluble fibrinogen, into the insoluble fibrin protein strands. Factor XIII then stabilizes the fibrin clot.

Identify which blood groups may be safely transfused into patients with different ABO types.

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.

Discuss the various steps in the life cycle of erythrocytes.

1. Hemopoiesis of erythrocytes begins in the hemopoietic bone marrow. 2. Reticulocytes are released into the bloodstream, where they mature into erythrocytes which they circulate for an average of 120 days 3. Old and damaged erythrocytes are phagocytized by macrophages in the bone marrow, liver, and spleen. 4. The globin (protein) portion of hemoglobin is metabolized into amino acids which are reused for protein synthesis. 5. The heme portion is broken down into biliverdin for transport in the blood. The iron ions bind to the blood protein transferrin for transport. 6. Unused heme groups can be recycled and used in hemopoiesis or can be converted into bilirubin and used to make bile in the liver. Iron ions can also be transferred to the protein ferritin for storage in the liver.

Identify the lineage and function of platelets.

A platelet is not a cell but rather a fragment of the cytoplasm of a cell called a megakaryocyte that is surrounded by a plasma membrane. typically 150,000-160,000 per µL of blood. After entering the circulation, approximately one-third migrate to the spleen for storage for later release in response to any rupture in a blood vessel. They then become activated to perform their primary function, which is to limit blood loss. Platelets remain only about 10 days, then are phagocytized by macrophages.

Discuss disorders affecting hemostasis.

Either an insufficient or an excessive production of platelets can lead to severe disease or death. As discussed earlier, an insufficient number of platelets, called thrombocytopenia, typically results in the inability of blood to form clots. This can lead to excessive bleeding, even from minor wounds. Thrombophilia, also called hypercoagulation, is a condition in which there is a tendency to form thrombosis. This may be familial (genetic) or acquired. Acquired forms include the autoimmune disease lupus, immune reactions to heparin, polycythemia vera, thrombocytosis, sickle cell disease, pregnancy, and even obesity. A thrombus can seriously impede blood flow to or from a region and will cause a local increase in blood pressure. If flow is to be maintained, the heart will need to generate a greater pressure to overcome the resistance.

Describe the basic physiological consequences of transfusion of incompatible blood.

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.

Discuss the pathophysiology of hemolytic disease of the newborn.

Hemolytic disease of the newborn is a risk during a subsequent pregnancy in which a RH- mother is carrying a second RH+ fetus

Classify leukocytes according to their main structural features and primary functions.

Neutrophils: 50-70% of total leukocyte count. 10-12cm in diameter, larger than erythrocytes. called neutrophils because their granules show up most clearly with stains that are chemically neutral. light lilac color. neutrophils are rapid responders to the site of infection and are efficient phagocytes with a preference for bacteria. Eosinophil: 2-4% of leukocyte count. 10-12cm in diameter. orange color. eosinophil granules contain molecules toxic to parasitic worms, which can enter the body through the integument. eosinophils are capable of phagocytosis and are effective when antibodies bind to the target and form an antigen-antibody. high counts are found in patients experiencing allergy, parasitic worms, and auto immune diseases. Basophils least common leukocytes typically comprising less than 1% of total leukocyte count. slightly smaller than neutrophils and eosinophils at 8-10cm in diameter. dark blue stain. intensify inflammatory response. release histamines which contribute to inflammation which opposes blood clotting. lymphocytes arise from lymphoid stem cells. form initially in the bone marrow. second most common type of leukocyte accounting for 20-30% of all leukocytes. essential for immune response. extensive in size, includes nature killers, t cells, and b cells. nature killers are capable for recognizing cells that do not express self proteins on their plasma membrane or that contain foreign or abnormal markers. b and t cells are prominent in roles of defending the body against specific pathogens and are involved in specific immunity. one form of b cells produces antibodies and t cells provide cellular level immunity by attacking foreign cells. monocytes represent 2-8% of total leukocyte count. horshoe like phagocytize debris, foreign pathogens, worn out erythrocytes, and dead worn out cells. attract leukocytes to the site of an infection. monocytes are associated with viral or fungal infections.

Compare and contrast ABO and Rh blood groups.

The red blood cells define the blood group you actually belong to. There are small markers known as antigens on the red cells surface, but they are so tiny that it cannot be viewed under a microscope. However, every person has different antigens but for identical twins. The antigens identify the blood types and are the key to match the transfusions as well that helps in avoiding serious complications. The blood group structure is defined as the ABO system. Another significant factor worth considering is the Rh system. All the blood groups have the possibility of having Rh antigens. Conversely, there are some who have it, while some do not have it. In case, the blood group belongs to Rh antigens, then they are Rh positive and a person having A blood group with Rh positive is recognized as A+. In case a person has A blood group with Rh negative, then it is A-. This is the same pattern followed for O, B or AB blood group as well. The Rh system duals the blood groups effectively so that the positive blood type does not get mixed with negative.

Identify the primary functions of blood transportation, defense, and maintenance of homeostasis.

Transportation: nutrients we eat are absorbed in the digestive tract. most travel in the bloodstream directly to the liver, where they are processed and released back into the bloodstream for delivery to body cells. blood picks up cellular wastes/byproducts & transports them to various organs for removal. Defense: WBCs protect the body from external threats, such as disease causing bacteria that have entered the bloodstream in a wound. other WBCs seek out/destroy internal threats such as mutated DNA cells that could multiply and become cancerous or body cells infected with viruses. when damage to vessels results in bleeding, blood platelets/certain proteins interacts to block the ruptured areas of the blood vessels involved, protecting from further blood loss. Homeostasis: on a warm day, your rising body core temp would trigger several homeostatic mechanisms, increased transport of blood from your core to your body periphery, which is typically cooler. as blood passes through your skin vessels, heat would be dissipated to the environment, and blood returning to your body would be cooler. on a cold day, blood is diverted away from the skin to maintain a warmer body core. 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.

Describe the three mechanisms involved in hemostasis.

When a vessel is severed or punctured, or when the wall of a vessel is damaged, vascular spasm occurs. In vascular spasm, the smooth muscle in the walls of the vessel contracts dramatically. The vascular spasm response is believed to be triggered by several chemicals called endothelins that are released by vessel-lining cells and by pain receptors in response to vessel injury. This phenomenon typically lasts for up to 30 minutes, although it can last for hours. Formation of Platelet Plug-platelets, which normally float free in the plasma, encounter the area of vessel rupture with the exposed underlying connective tissue and collagenous fibers. The platelets begin to clump together, become spiked and sticky, and bind to the exposed collagen and endothelial lining. A platelet plug can temporarily seal a small opening in a blood vessel. Plug formation, in essence, buys the body time while more sophisticated and durable repairs are being made. Coagulation, the formation of a blood clot. The process is sometimes characterized as a cascade, because one event prompts the next as in a multi-level waterfall. The result is the production of a gelatinous but robust clot made up of a mesh of fibrin—an insoluble filamentous protein derived from fibrinogen, the plasma protein introduced earlier—in which platelets and blood cells are trapped.

Explain the composition and function of hemoglobin.

a large molecule made up of proteins and iron. consists of four folded chains of a protein called globin. each iron ion in the heme can bind to one oxygen molecule. each hemoglobin molecule can transport 4 oxygen molecules. An individual erythrocyte may contain about 300 million hemoglobin molecules, and therefore can bind to and transport up to 1.2 billion oxygen molecules

Describe the anatomy of erythrocytes.

erythrocytes are biconcave disks. they are plump at their periphery and very thin in the center. they lack most organelles, there is more interior space for the presence of the hemoglobin molecules that transports gases. the biconcave shape provides a greater surface area across at which gas exchange can occur. erythrocytes may stack up much like a roll of coins, forming a rouleaux, from the French word "roll"

Describe the general characteristics of leukocytes.

far less numerous than erythrocytes. larger than erythrocytes and are the only formed elements that are complete in cells, possessing a nucleus and organelles. many types of leukocytes. most have a shorter lifespan than erythrocytes. some are lasting for a few hours or even a few hours or even a few minutes, in case of an acute infection. routinely leave the bloodstream to perform their defensive functions in the body's tissues. once they leave the capillaries they take up positions in the lymphatic tissue, bone marrow, spleen, thymus, or other organs.

Discuss the unique physical characteristics of blood.

pH averages to be 7.4, can range from 7.35-7.45 in a healthy person. more basic than pure water. blood makes up 8% of adult body weight. adult males average 5-6 liters of blood; females average 4-5 liters. blood taking up oxygen to the lungs is bright red, blood releasing oxygen is dusky red. viscosity is about 5x's greater than water. normal temp is 38 degrees celsius compared to the bpdy's temp which is 37 degrees celsius.

Identify the composition of blood plasma, including its most important solutes and plasma proteins.

plasma is composed primarily of water: In fact, it is about 92 percent water. About 7 percent of the volume of plasma—nearly all that is not water—is made of proteins. -albumin is the most abundant. molecules serve as binding proteins--transport vehicles for fatty acids and steroid hormones. albumin is the most significant contributor to the osmotic pressure of blood. its presence holds water inside the blood vessels and draws water from tissues across blood vessel walls, and into bloodstream. helps maintain blood volume and blood pressure. accounts for 54% of total plasma protein content. -globulins alpha/beta globulins transports iron, lips, and the fat soluble vitamins A, D, E, and K to the cells. also contributes to osmotic pressure. gamma globulins are proteins involved with immunity and are better known as antibodies or immunoglobulins. makes up 38% of total plasma volume. -fibrinogens produced by the liver like albumin & alpha & beta globulins. essential for blood clotting, accounts for 7% of total plasma protein volume 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.

Trace the generation of the formed elements of blood from bone marrow stem cells.

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