BIOL 221 – Blood Lecture Notes PDF

BIOL 221 – Blood Cristofre Martin Department of Biochemistry St. George’s University  Lecture Objectives: Describe the composition of blood. List the functions of blood? Describe the characteristics and formation of erythrocytes/ red blood cells(RBCs). List the composition p...

BIOL 221 – Blood Cristofre Martin Department of Biochemistry St. George’s University  Lecture Objectives: Describe the composition of blood. List the functions of blood? Describe the characteristics and formation of erythrocytes/ red blood cells(RBCs). List the composition plasma and the function of each of its constituents. Describe recycling of RBC breakdown products. Describe the differentiation of leukocytes/ white blood cells (WBCs). List the % composition of each of the blood cells. Describe the function of each of the blood cells. Describe heme and hemoglobin. Describe the formation of a blood clot and the response to vascular vessel damage. Describe the common causes of anemia Describe the ABO and Rh blood groups Compare the compatibility of blood donation (transfusion reaction) between individuals with different blood types. List the incidence of blood groups between persons of different ethnic backgrounds  Functions of Blood The body contains about 4-6 liters of blood Transport of O2, CO2, nutrients, hormones and waste. Regulation of pH at between 7.35 – 7.45 Maintain body temperature and water content of cells. Protection from blood loss through clotting Protection from disease through phagocytic white blood cells and antibodies. The average adult has 4-6 liters of blood. Approximately 0.5 l is removed during a blood donation. Blood consists of cellular elements suspended in liquid (plasma). The Primary Constituents of Human Blood  Plasma Plasma comprises 55% of the blood, consisting of: – water ~91.5% of plasma – salts (including bicarbonate) which affect osmotic balance, buffering, membrane permeability. – Plasma proteins affect osmotic balance, pH buffering, clotting, immunity. – Transported substances, such as nutrients, respiratory gases, waste products, hormones. Albumin (54%): binds cations, fatty acids, hormones and regulates osmostic pressure Globulin (38%): immune system Fibrinogen (7%): blood clotting Red blood cells RBCs, erythrocytes, are the most numerous blood cells. There are ~4.5 million RBCs/ul of blood. Mature RBCs are enucleated (non- dividing), resulting in their biconcave shape. This provides greater surface area for gas exchange than a flat disc or sphere has. High hemoglobin content (280 million molecules per RBC). RBCs are small, ~7-8 microns in diameter. Lifespan: 100-120 days before removal by Hemoglobin (Hb) Each RBC has ~ 250,000,000 molecules of Hb. A Hb molecule consists of 4 polypeptide chains, each with an iron- containing complex. As RBCs pass through the capillary beds of the lungs, O2 diffuses into the rbcs and binds with iron in Hb to form oxyHb. Lower O2 tension in systemic capillaries stimulates Hb to release O2 to the tissues deoxyHb Blood with oxyhemoglobin is bright red. Blood with deoxyhemoglobin is dark purple-red. 1/60 of blood O2 is found in plasma, and the remainder is carried by Hb. When exposed to CO, Hb combines with it and remains bound to it. Hb is then unavailable for O2 transport and results in carbon monoxide poisoning and often is fatal.  Erythropoiesis RBCs are formed in bone marrow. RBC production is controlled by a mechanism sensitive to the amount of O2 reaching the tissues. If tissues do not receive enough O2, kidneys secrete erythropoietin, stimulating bone marrow to produce more RBCs. RBCs circulate 90-120 days before breakdown in the liver, spleen and bone marrow.  Hemoglobin breakdown Products and Reuse Amino acids from hemoglobin are used to make other proteins. Bile pigments from hemoglobin are used in bile production. Most iron is returned to the bone marrow, to be incorporated in the hemoglobin of new rbcs.  Anemia Anemia is an abnormally low amount of hemoglobin or RBCs. Anemia can result from too little iron or folic acid, or from excessive blood loss. Pernicious anemia: GI tract is unable to absorb vitamin B 12. (remember intrinsic factor...secreted by parietal cells) B12 is essential for RBC formation. Vitamin B12 injections often help. Hemolytic anemia is seen in sickle-cell disease; sickle- shaped RBCs often rupture. Bone marrow cancer can cause anemia.  White blood cells WBCs, leukocytes, are formed in the bone marrow. There are 5000-9000 per ul. of blood. Leukocytes fight infection. WBC life span: most WBCs: a few days WBCs squeeze between endothelial cells in the capillaries, and can be found in the lymphatic system and tissue fluid. Granulocytes: Agranulocytes: Basophils Monocytes Eosinophils Lymphocytes Neutrophils  Normal distribution of wbcs: Neutrophils 50-70% Lymphocytes 20-40% Monocytes 1-10% Eosinophils 0-3% Basophils 0-1% Based on the knowledge that different WBCs increase in number in response to varied stimuli, differential WBC counts are a standard laboratory request.  Hemopoiesis (blood cell formation) is Stimulated by Hormones RBC: Erythropoietin Platelets: Thrombopoietin WBC’s: Colony- stimulating Factors (4) Basophils: large basophilic, blue staining granules that obsures the nucleus contain histamine and heparin that is released during allergic response involved in inflammatory response Eosinophils: have a bi-lobed nucleus acidophilic (red staining) granules that does not obsure the nucleus counteracts histamines in allergic responses phagocytic on antigen/antibody complexes involved in fighting parasitic infections  et te l pla Neutrophils: nuclei possess 2-5 lobes contains fine purple granules phagocytic cells that engulf bacteria Agranulocytes: Monocytes 5. are the largest wbcs with fine pink granules and an indented nucleus. They migrate from the blood to the liver, spleen, lungs, etc. where they function as macrophages. Monocytes: kidney shaped nucleus cytoplasm in slightly basophilic and non-granular they are phagocytic cells involved in fighting viral and fungal infections Lymphocytes: nucleus is round and slightly indented cytoplasm forms a rim around the nucleus B-lymphocytes produce antibodies T-lymphocytes attack viruses, cancer cells and transplated tissues They also give rise to connective tissue plasma cells Platelets and Vascular Damage Megakaryocytes in bone marrow fragment, and pieces pass into the blood as platelets. When endothelial cells are damaged, CT tissue in the vessel wall is exposed to blood. Steps of Clot Formation: 1.Platelet adhesion: Platelets in the vicinity adhere to exposed CT and release a sticky substance Platelets cluster together, forming a plug. 2. Platelet Release Reaction: Activated platelets extend projections and make contact with each other Granules are released that contain ADP and thromboxane A2 that activates other platelets. Serotonin and thromoboxane A2 causes vasoconstriction to limit blood flow to the area 3. Platelet Aggregation: ADP makes platelets sticky and new platelets adhere to other platelets forming a plug 4.Blood Clotting: Thrombin converts fibrinogen protein to fibrin Fibrin assists in clot formation by infiltrating the plug with a fibrous mesh.  Blood typing Antigens are substances that stimulate the production of antibodies when introduced into a new environment. Antibodies then cause antigen-containing cells to clump together (agglutination). In extreme cases, where a great deal of antigen is present, such as in a blood transfusion, agglutination can block small vessels, and hemolysis occurs. Kidneys are particularly vulnerable to damage. A and B antigens are glycolipids on RBCs and are used to type blood. Human blood may have A, B, A and B, or no antigen. When an antibody is exposed to its antigen, a negative reaction occurs. (agglutination)  Blood types Antigens present on RBC surface specify blood type Major antigen group is ABO system – Type A blood has only A antigens – Type B has only B antigens – Type AB has both A & B antigens – Type O has neither A or B antigens  Transfusion Reactions People with Type A blood make antibodies to Type B RBCs, but not to Type A Type B blood has antibodies to Type A RBCs but not to Type B Type AB blood doesn’t have antibodies to A or B Type O has antibodies to both Type A & B If different blood types are mixed, antibodies will cause mixture to agglutinate  If a person has A and B antigens, he will have no antibodies, and can receive any blood type. (universal recipient.) To whom can he give blood? If one has no antigens (O) he can give to anyone (universal donor). A person with type O blood has A and B antibodies. If he receives a transfusion from an A, B, or AB donor, his antibodies will react.  Hypothetical Scenario: Your ship hits an iceberg, and you are now in a life raft with 6 other people. Two people, one from Japan and another from Zimbabwe, are desperately in need of blood. You have equipment that can be used for blood transfusions, but there is no means of typing blood. The five healthy people are a black man, a white man, a Chinese woman, a Korean man and a native American (Indian) woman. Whose blood should be given to each injured person?  Rh factor Another major factor in blood typing is Rh. 85% of the population have Rh factor (Rh+). If a person who has this factor is exposed to blood that does not have it, no reaction will occur. A person missing Rh factor (Rh-) does not automatically have Rh antibodies; however, if exposed to Rh factor, he/she will begin forming Rh antibodies.  Rh incompatability When an Rh- mother bears an Rh+ fetus, problems may arise. The blood:placental barrier is fairly effective during normal pregnancy. As the placenta separates from the uterus during delivery, leakage of blood between maternal:fetal systems can occur. As Rh antigens enter her system, the Rh- mother may develop Rh antibodies. If the mother bears a second baby, mingling of blood may again occur.  Rh incompatability II The baby will then receive Rh antibodies. If baby is Rh+, hemolysis can occur, with breakdown of hemoglobin: Excess bilirubin can accumulate, leading to retardation and even death. Solution: within 72 hrs of 1st birth, give mother immunoglobulin containing Rh antibodies. It will destroy any Rh antigens in the mother’s blood, before they can stimulate antibody formation.