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Blood Chapter 17 Blood Composition and Characteristics Major Components: Plasma Leukocytes Platelets Erythrocytes Hematocrit = % RBC volume of total blood volume. Females have about 42%, males have about 47% (+/- 5%) Fig 17.1 Figure 17.1 Blood Composition and Characteristics Characteristics of Blood: Denser, more viscous than water Volume of blood: 4-5L (F), 5-6L (M). Normal pH: 7.35 – 7.45 Functions of Blood 1. Distribution Delivery of O2 and other nutrients to all cells of the body Transport of metabolic wastes to sites of elimination Transport of hormones to target organs 2. Regulation Maintaining body temperature Maintaining pH of tissues via protein buffers and bicarbonate Maintaining proper fluid volume in circulatory system and tissues 3. Protection Preventing blood loss through hemostasis Preventing infection via antibodies, complement, and WBCs Plasma Composition Water 90% of plasma volume Solutes 10% of plasma volume ~8% Proteins Globulins- transport proteins (eg. albumin) and antibodies (immunoglobulins) Clotting proteins (eg. fibrinogen) Others: enzymes, hormones Metabolic wastes ~2% Nutrients Electrolytes Respiratory Gases urea, lactic acid, creatinine glucose, amino acids, vitamins, lipids Na+,K+,Ca2+, Cl-, P04-, bicarbonate O2, CO2 Blood Cells/Formed Elements Erythrocytes-Red Blood Corpuscles Characteristics: biconcave shape, ~7.5 mm diameter 5 million/microliter Function: respiratory gas tranpsort, via binding/unbinding to hemoglobin. (O2 and CO2) Hemoglobin: protein globin + heme pigment Contained within erythrocytes @ 12-20 g/100 ml blood 4 globin subunits/Hb; each one has 1 heme that binds 1 O2 molecule. Fig. 17.2 Erythrocytes-Red Blood Corpuscles Characteristics: biconcave shape, ~7.5 mm diameter Function: respiratory gas transport via binding/unbinding to hemoglobin (O2 and CO2) Hemoglobin: protein globin + heme pigment contained within erythrocytes 4 globin subunits/Hb; each one has 1 heme that binds 1 O2 molecule Oxygen-Hemoglobin dissociation curve Erythrocytes Erythropoesis: genesis of red blood cells begins with hemocytoblast stem cell stimulated by erythropoetin released from the kidneys erythropoetin (EPO)-glycoprotein hormone released predominantly from the kidneys but also from the liver Recombinant products: Epogen or procrit. Fig 17.6 Erythrocytes Fate and Destruction: life time- 100-120 days degraded in the spleen,liver by macrophages iron released from heme and recycled remainder of heme-degraded to converted to bile by the liver Leukocytes- White blood cells Granulocytes- contain cytoplasmic granules that stain with Wright’s stain; often lobed nuclei neutrophils- most numerous WBCs; also called (polymorphonucleocytes) function in inflammation and destroy bacteria via defensins (proteins) and phagocytosis eosinophils- attack parasitic worms by releasing enzymes from granules, also destroys Ag/Ab complexes. basophils- release the inflammatory chemical histamine from granules Leukocytes-White blood cells Agranulocytes- lack visible cytoplasmic granules spherical or kidney-shaped nuclei lymphocytes- most live in lymphoid tissue, but some circulate in the blood T & B lymphocytes monocytes-differentiate into macrophages within tissues (phagocytic cells) Production of Leukocytes Hemocytoblast Myeloid stem cell Lymphoid stem cell Platelets Platelets: cytoplasmic fragments of megakaryocytes that play a role in blood clot formation also called thrombrocytes Production of platelets: stimulated by thrombopoietin (Tpo) Hemocytoblast Megakaryocyte fragmentation platelets Hemostasis- Complex series of reactions that stop bleeding after a blood vessel is injured; involves numerous clotting factors (including fibrinogen, prothrombin, Ca2+) optional Blood Types optional reading pp 654-658