BIOL 244 Chapter 17: BloodLecture 8 (September 16) Erythrocytes (RBCs) Disc-shaped cell with thick rim No mitochondria- Anaerobic fermentation to produce ATP Functions Carry oxygen from lungs to cell tissues Pick up carbon dioxide from tissues and bring to lungs  Blood type determined by surface proteins and glycolipids Erythrocytes and hemoglobin concentration indicate amount of oxygen blood can carry Hematocrit (packed cell volume)- percentage of whole blood volume composed of erythrocytes - Men 42-52%- Women 37-48% Hemoglobin concentration of whole blood- Men 13-18 g/dL- Women 12-16 g/dL Hemoglobin (Hb) Structure Globin: formed by 4 protein chains (2 alpha and 2 beta chains) 4 heme groups: nonprotein moiety that binds O2 to ferrous ion (Fe2+) at its center Erythrocyte production (erythropoiesis)  2.5 million RBCs produced per second Kidney production of erythropoietin stimulates bone marrow Development takes 3-5 days Average lifespan of about 120 days Stimuli for increasing erythropoiesis- Low levels of oxygen (hypoxemia)- High altitude- Increase in exercise  Anemia 3 categories- Inadequate erythropoiesis or hemoglobin synthesis Kidney failure and insufficient erythropoietin Iron-deficiency anemia Pernicious anemia: inadequate vitamin B12 from poor nutrition or lack of intrinsic factor Hypoplastic anemia: slowing of erythropoiesis Aplastic anemia: complete cessation of erythropoiesis (body cannot make RBCs)- Hemorrhagic anemias from bleeding- Hemolytic anemias from erythrocyte destruction Sickle-Cell Disease/Anemia Hereditary hemoglobin defects occur mostly among people of African descent  Caused by a recessive allele that modifies the structure of the hemoglobin molecule (Hbs)- Differs only on the 6th amino acid of the beta chain- HbS does not bind oxygen well- Erythrocytes become rigid, sticky, pointed at ends- Clump together and block small blood vessels causing intense pain- Can lead to kidney or heart failure, stroke, rheumatism, or paralysis Blood types are based on interactions between antigens and antibodies Antigens: complex molecules on surface of cell membrane that are unique to the individual Used to distinguish self from foreign substances Foreign antigens generate an immune response Antibodies: proteins (gamma globulins) secreted by plasma cells Part of immune response to foreign matter Bind to antigens and mark them for destruction Forms antigen-antibody complexes Agglutination: antibody molecule binding to antigens, causing clumping of erythrocytes  A, B, and O blood type is determined by presence or absence of antigens (agglutinogens)on erythrocytes Blood type A person has A antigens Blood type B person has B antigens Blood type AB has both A and B antigens Blood type O has neither A nor B antigens- Type O is most common blood type- Type AB is rarest blood type Rh group Rh (C, D, E) agglutinogens discovered in rhesus monkey in 1940- Rh+ if person has D antigen on erythrocytes Anti-D agglutinins not normally present- Form in Rh- individuals exposed to Rh+ blood Rh- woman with an Rh+ fetus or transfusion of Rh+ blood No problems with first transfusion or pregnancy Leukocytes (WBCs) Least abundant formed element Protects against infectious microorganisms and other pathogens Conspicuous nucleus Spends only a few hours in the blood stream before migrating to connective tissue Retain their organelles for protein synthesis Granules- granulocytes have specific granules that contain enzymes and other chemicals employed in defense against pathogens Types: Granulocytes:- Neutrophils Polymorphonuclear  60-70% 3-5 lobed nucleus Functions: Increased numbers in bacterial infections Phagocytosis of bacteria Release antimicrobial chemicals- Eosinophils 2-4% Large rosy, orange granules Bilobed nucleus Functions: Increased numbers in parasitic infections, collagen diseases, allergies, diseases of spleen and CNS Phagocytosis of antigen-antibody complexes, allergens, & inflammatory chemicals Release enzymes to destroy large parasites- Basophils <1% Large, abundant, violet granules Large S-shaped nucleus Functions: Increased numbers in chicken pox, sinusitis Secrete histamine (vasodilator): speeds flow of blood to an injured area Secrete heparin (anticoagulant): promotes the mobility of other erythrocytes in the area Agranulocytes- Lymphocytes  25-33% Round, uniform dark violet nucleus Functions: Increased numbers in diverse infections and immune responses Destroy cells (cancer, foreign, & virally infected cells) Coordinate actions of other immune cells Secrete antibodies and provide immune memory- Monocytes 3-8% Largest leukocyte Horseshoe-shaped nucleus  Functions: Increased numbers in viral infections and inflammation Leave bloodstream and transform into macrophages Phagocytize pathogens and debris Leukopoiesis- production of leukocytes Pluripotent stem cells (PPSCs)- Myeloblasts: form neutrophils, eosinophils, basophils- Monoblasts: form monocytes- Lymphoblasts: give rise to all forms of lymphocytes- T lymphocytes: complete development in thymus Disorders Leukopenia- low WBC count below 5000/uL- Causes: radiation, poisons, infectious disease- Effects: elevated risk of infection Leukocytosis- high WBC count about 10,000/uL- Causes: infection, allergy, and disease- Differential WBC count- identifies what percentage of the total WBC count consist of each type of leukocytes Leukemia- cancer of hemopoietic tissue that usually produces an extraordinary high number of circulating leukocytes and their precursors  Thrombocytes (Platelets)- small fragments of megarkaryocyte cells Contain granules Amoeboid movement and phagocytosis Hemostasis- the cessation of bleeding Stopping potentially fatal leaks Hemorrhage- excessive bleeding 3 steps:- Vascular spasm- Platelet plug formation- Blood clotting (coagulation) Mechanism- Vascular spasm- prompt constriction of a broken vessel Most immediate protection against blood loss- Platelet plug formation Broken vessel exposes collagen Platelet pseudopods stick to damaged vessel and other platelets: pseudopodscontract and draw walls of vessel