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Chapter 13
Blood Composition and Volume
Blood is liquid connective tissue and the major transporting media of the body. Function of Blood o Blood is the transporting fluid of the body. It carries oxygen from the lungs to the cells, nutrients from the digestive tract to the cells, metabolic waste products from the cells to the various organs of excretion, and hormones from secreting cells to other parts of the body. o It aids in the distribution of body heat formed in the more active tissues (such as the skeletal muscles) to all parts of the body. o Blood also helps to regulate the acid-base balance and to protect against infection. Composition of blood -
- Plasma -Liquid fraction of whole blood (extracellular part). 55% of whole blood is plasma.
- Cellular components- suspended in the plasma make up formed elements. 45% of whole blood is cellular component. Normal volumes of blood o Plasma—2.6 L average o Formed elements (Blood Cells)—2.4 L average o Whole blood—4 to 6 L average in an adult, or 7% to 9% of total body weight Blood pH: Blood is alkaline/basic—pH 7.35 to pH 7. A. Blood plasma Liquid portion of whole blood or blood minus formed elements
Composition of plasma Water is the main component of plasma containing many dissolved substances including: a. Foods (Nutrients), salts, hormones b. O 2 (Oxygen), and CO 2 (carbon di oxide) d. plasma proteins include (1) Albumins- Helps in maintaining water balance (2) Globulins- include the antibodies that help protect us from infections (3) Fibrinogen-helps in blood clotting (4) Prothrombin- helps in blood clotting Serum - - Plasma minus clotting factors is called serum. Serum is liquid remaining after whole blood clots. Serum contains antibodies.
B.Cellular components (Formed elements) There are three main types and several subtypes of formed elements:
- Red blood cells (RBCs), or erythrocytes
- White blood cells (WBCs), or leukocytes a. Granular leukocytes (have stained granules in their cytoplasm) 1. Neutrophils 2. Eosinophils 3. Basophils b. Agranular leukocytes (do not have stained granules in their cytoplasm) 1. Lymphocytes 2. Monocytes
- Platelets or thrombocytes
Blood Cell Count a. RBCs —4.2 to 6.2 million/mm^3 of blood b. WBCs —5000 to 10,000/mm^3 of blood c. Platelets —150,000 to 340,000/mm^3 of blood
Blood Cell Formation a. Red bone marrow (myeloid tissue) forms all blood cells except some lymphocytes and monocytes. b. Monocytes and lymphocytes are formed by lymphatic (lymphoid) tissue in the lymph nodes, thymus, and spleen
Mechanisms of Blood Disease
o Most blood diseases result from failure of myeloid (red bone marrow) and lymphatic tissues to form blood cell properly. o Causes include toxic chemicals, radiation, inherited defects, nutritional deficiencies and cancers, including leukemia o Aspiration biopsy cytology (ABC) permits examination of blood-forming tissues to assist in diagnosis of blood diseases o Bone marrow, cord blood, and hematopoietic stem cell transplants may be used to replace diseased or destroyed blood-forming tissues
Red Blood Cells (Erythrocytes)
o Biconcave disk shape (thin center and thicker edges) results in large cellular surface area. o Mature RBC has no nucleus (enucleated) and usual life span is about 120 days. o RBC contain a protein that carries oxygen called hemoglobin (Hb) o Red blood cells are formed in the red bone marrow called erythropoiesis or hematopoiesis.
Hemoglobin :
Blood types
Blood types are identified by certain antigens in red blood cells (RBCs). An antigen is a protein substance present on the surface of cell that can stimulate the body to make antibodies. Almost all substances that act as antigens are foreign proteins. Antibody is a substance made by the body in response to stimulation by an antigen. Many antibodies react with their antigens to cause clumping; that is, they agglutinate the antigens. Blood is identified as a specific "type" by using the ABO and Rh systems of classification
- ABO system -depends on A antigen or B antigen Type A blood—type A antigens present in the plasma membrane of RBCs and anti-B type antibodies in plasma Type B blood—type B antigens present in the plasma membrane of RBCs; and anti-A type antibodies in plasma Type AB blood—type A and type B antigens in the plasma membrane of RBCs; no anti-A or anti-B antibodies in plasma; called universal recipient blood Type O blood—no type A or type B antigens in the plasma membrane of RBCs; both anti-A and anti-B antibodies in plasma; called universal donor blood 2_._ Rh system- depends on Rh antigen Rh-positive blood—Rh factor antigen present in RBCs Rh-negative blood—no Rh factor present in RBCs; no anti-Rh antibodies present naturally in plasma; anti-Rh antibodies, however, appear in the plasma of Rh-negative persons if Rh- positive RBCs have been introduced into their bodies ABO Blood group System
Hemolytic disease of newborn and erythroblastosis fetalis o Caused by blood ABO or Rh factor incompatibility during pregnancy between developing baby and mother where the mother is Rh-negative, and father is Rh-positive, and the baby is Rh-positive. o Rh-positive blood cells from the baby are introduced into an Rh-negative mother’s body and anti-Rh antibodies soon appear in the mother’s blood plasma. Rh incompatibility isn’t as much of a concern for the first baby. But in subsequent pregnancy, this Rh-antibody will attack the Rh-antigen of the baby and destroys featal RBC(If the next baby is Rh-positive). it may develop a type of hemolytic anemia called erythroblastosis fetalis, caused by the mother’s Rh antibodies reacting with the baby’s Rh- positive cells o This condition can be prevented by administration of RhoGAM to Rh negative mothers
Red Blood Cell Disorders Polycythemia Cause is generally cancerous transformation of red bone marrow Dramatic increase in RBC numbers—often in excess of 10 million/mm^3 of blood. Signs and symptoms include: o Increased blood viscosity or thickness o Slow blood flow and coagulation problems o Frequent hemorrhages o Distention of blood vessels and hypertension Treatment may include: o Blood removal o Irradiation and chemotherapy to suppress RBC production Anemia Caused by low numbers or abnormal RBCs or by low levels or defective types of hemoglobin Normal hemoglobin ranges: Adult females-12 to 14 grams per 100 mL of whole blood. Adult females - 14 to 17 grams per100 mL of whole blood. A hemoglobin value less than 9 g/100 mL indicates anemia. Normal Hb levels 12 to 14 g/100 ml of blood Low Hb level (below 9 g/100 ml of blood) classified as anemia Majority of clinical signs of anemia related to low tissue oxygen levels o Fatigue; skin pallor o Weakness; faintness; headache o Compensation results in increased heart and respiratory rates
Different types of anemias Hemorrhagic anemia o Acute blood loss anemia—blood loss is immediate (for example, surgery or trauma) o Chronic blood loss anemia—blood loss is immediate (for example, surgery or —blood loss occurs over time (for example, ulcers or cancer) o Once the actual bleeding is stopped, transfusion of whole blood or red cells and successful treatment of the underlying reason for chronic blood loss are curative. Aplastic anemia o Characterized by low RBC numbers and destruction of bone marrow o Often caused by toxic chemicals, radiation, or certain drugs
Deficiency anemias —caused by inadequate supply of some substance needed for RBC or hemoglobin production a. Pernicious anemia - o Results from a dietary deficiency of vitamin B12 or from the failure of the stomach lining to produce intrinsic factor—the substance that allows vitamin B12 to be absorbed.
o Leukopenia—abnormally low WBC count (below 5000/mm^3 of blood) o Leukocytosis—abnormally high WBC count ((over 10,000/mm^3 of blood)
WBC or Leukocyte types and functions
- Granulocytes a. Neutrophils o Most numerous type of WBCs called phagocytes o Perform phagocytosis (engulf the infectious agents) o Numbers increase in bacterial infections. b. Eosinophils o Weak phagocyte o Active against parasitic infection and parasitic worms. Involved in allergic reactions c. Basophils o Related to mast cells in tissue spaces o Both mast cells and basophils secrete histamine (related to inflammation) o Basophils also secrete heparin which act as an anticoagulant (prevent blood from clotting in the circulation)
- Agranulocytes a. Monocytes o Aggressive phagocyte—capable of engulfing larger bacteria and cancer cells o Develop into much larger cells called macrophages after leaving blood to enter tissue spaces b. Lymphocytes o B Lymphocytes -Develop within several lymphoid organs of the body. B lymphocytes (B cells) secrete plasma proteins called antibodies that attach to specific molecules related to bacteria, viruses, chemical toxins, or other foreign substances to destroy or neutralize them. o T lymphocytes -Develop in the thymus. They do not secrete antibodies but instead protect us by directly attacking bacteria, virus-infected cells, or cancer cells.
White Blood Cell Disorders
Leukemia is the term used to describe a number of blood cancers affecting the WBCs. In almost every form of leukemia, marked leukocytosis, or elevated WBC levels, occur. The different types of leukemia are identified as either acute or chronic, based on how quickly symptoms appear after the disease begins, and as lymphocytic or myeloid depending on the cell type involved. Four of the most common leukemia are: o Chronic lymphocytic leukemia (CLL) most often affects older adults and is rare in individuals younger than 30 years of age. In those with CLL, malignant precursor B lymphocytes are produced in great numbers but do not produce normal antibodies and, as a result, some increase in infections may occur. Anemia, fatigue, and development of enlarged but generally painless lymph nodes is common. Many patients with CLL live many years after diagnosis with little or no treatment. More severe cases often benefit from chemotherapy and irradiation. o Acute lymphocytic leukemia (ALL) is primarily a disease of children and constitutes the most common form of "blood cancer" in children between 3 and 7 years of age. Although always a serious condition, it is highly curable in children but less so when it occurs in adults. Onset of the disease is sudden and often marked by fever, bone pain, and increased rates of infection and anemia. Treatment may involve chemotherapy, irradiation, and bone marrow or stem cell transplants. o Chronic myeloid leukemia (CML) accounts for about 20% of all cases of leukemia and occurs most often in adults between 25 and 60 years of age. CML results from cancerous transformation of granulocytic (neutrophil, eosinophil, and basophil) precursor cells in the bone marrow. Onset is slow and early symptoms, such as fatigue, weakness, and weight loss, tend to be nonspecific. Bone marrow transplants are curative in up to 70% of cases. The recent introduction of a new "rational" or "designer" drug called Gleevec constitutes a major advance in treatment of CML. It specifically seeks out and blocks the flawed signals in CML cancer cells that cause runaway proliferation.
o Acute myeloid leukemia (AML): The pathological transformation of myeloid stem cells resulting in acute myeloid leukemia (AML) accounts for 80% of all cases of acute leukemia in adults and 20% of acute leukemia in children. As the name suggests, onset is sudden, and once symptoms appear, the disease progresses rapidly. Patients most often seek help because of fatigue, bone and joint pain, spongy bleeding gums, symptoms of anemia, and recurrent infections. The prognosis in AML is poor. Multiple myeloma Multiple myeloma is cancer of mature, antibody-secreting B lymphocytes called plasma cells (Figure 13-12). It is the most common and one of the most deadly forms of blood-related cancers in people older than 65 years of age. The cancerous transformation of plasma cells results in impairment of bone marrow function, production of defective antibodies, recurrent infections, anemia, and the painful destruction and fracture of bones in the skull, vertebrae, and throughout the skeletal system. Infectious mononucleosis Infectious mononucleosis is a common noncancerous WBC disorder appearing most often in adolescents and young adults between 15 and 25 years of age. The disease is usually caused by the Epstein-Barr virus (EBV), found in the saliva of infected individuals. “Mono” can be spread by kissing or any other direct contact with an infected person’s saliva, such as sharing a straw, toothbrush, or eating utensil.
Platelets and Blood Clotting
Platelets Platelets play an essential part in blood clotting. Plasma protein prothrombin and fibrinogen are required for blood clotting. Another substance calcium must be present in all steps of blood clotting for proper clotting. Blood Clotting Process: Blood clotting process is composed of a chain of rapid-fire reactions. The first step in the chain is any injury to a blood vessel makes a rough spot in its lining of it. (Normally the lining of blood vessels is extremely smooth.) Almost immediately, damaged tissue cells release particular clotting factors into the plasma. These factors rapidly react with other factors already present in the plasma to form prothrombin activator. At the same time platelets become "sticky" at the point of injury and soon accumulate near the opening in the broken blood vessel, forming a soft, temporary platelet plug. As the platelets accumulate, they release additional clotting factors, forming even more prothrombin activator. If the normal amount of blood calcium is present, prothrombin activator triggers the next step of clotting by converting prothrombin (a protein in normal blood) to thrombin. In the last step, thrombin reacts with fibrinogen (a normal plasma protein) to change it to a fibrous gel called fibrin. Fibrin threads form a tangle to trap RBCs and other formed elements to produce a blood clot
Physicians sometimes prescribe vitamin K before surgery to make sure that the patient's blood will clot fast enough to prevent hemorrhage. Vitamin K stimulates liver cells to increase the synthesis of prothrombin. More prothrombin in blood allows faster production of thrombin during clotting and thus faster clot formation. The anticoagulant warfarin sodium (Coumadin) acts by inhibiting the synthesis of prothrombin and other vitamin K-dependent clotting factors. Heparin also can be used to prevent excessive blood clotting. Heparin inhibits the conversion of pro- thrombin to thrombin, thus preventing formation of a thrombus. A clot-dissolving substance called tissue plasminogen activator (TPA or t-PA) is often used to dissolve clots that block the arteries that supply the heart muscle. Prothrombin time is the time taken by blood to clot.
Clotting Disorders
Thrombus: When a clot stays in the place where it formed, it is called a thrombus and the condition is spoken of as thrombosis.
