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Blood Chapter 12 Blood • • • • • Specialized CT Transports materials Maintains stability of interstitial fluid Distributes heat Amount varies with body size, fluid concentration changes, electrolyte concentration changes • ~8% of body weight • ~5L = adult blood volume Blood Cells • Form mostly in the red bone marrow • Includes: – Red Blood Cells (RBCs) – White Blood Cells (WBCs) – Platelets (cell fragments) • Blood cells form from: Hemocytoblasts in the red marrow Hematopoietic stem cells in the red marrow Capillary tube Plasma = 55% Mostly water, solutes (like proteins, electrolytes, some gases) Buffy coat Leukocytes & platelets (<1%) Red cells = 45% (hematocrit) Plug Blood 45% 55% Formed elements Platelets (4.8%) Red blood cells (95.1%) Plasma White blood Water Proteins Wastes Nutrients Gases cells Electrolytes (92%) (7%) (0.1%) Vitamins Hormones BasophilsMonocytesLymphocytes Neutrophils Eosinophils Albumins Globulins Fibrinogen (<1%) (25–33%) (3–9%) (54–62%) (1–3%) N2 O2 CO2 Red Blood Cells (Erythrocytes) • • • • Biconcave discs One-third hemoglobin Lack nuclei and mitochondria RBC count = the number of RBCs in a cubic millimeter or microliter of blood RBC Production • Low blood oxygen signals kidneys & liver to release erythropoietin (EPO) – Stimulates RBC production – Feedback mechanism? • New RBCs appear in the circulating blood within a few days Factor Vitamin B12 Source Absorbed from small intestine Function DNA synthesis Iron Absorbed from small intestine; conserved during RBC destruction Hemoglobin synthesis Folic acid Absorbed from small intestine DNA synthesis Types of Anemia Type Aplastic anemia Cause Defect Toxic chemicals, Damaged bone radiation marrow Hemolytic anemia Toxic chemicals RBCs destroyed Iron deficiency Dietary lack of iron Hb deficient anemia Pernicious anemia Inability to absorb Excess of B12 immature cells Sickle cell disease Defective gene Misshapen RBCs Thalassemia Defective gene Hb deficient; RBCs short-lived White Blood Cells (Leukocytes) • Protect against disease • Five types of WBCs (two categories): – Granulocytes • Neutrophils • Eosinophils • Basophils – Agranulocytes • Lymphocytes • Monocytes Neutrophils • Light purple granules when in neutral (acid-base) stain • Lobed nucleus • First to arrive at infections • Phagocytic • 54-62% of leukocytes • Elevated in bacterial infections Eosinophils • • • • • • Deep red granules in acid stain Bi-lobed nucleus Moderate allergic reactions Defend against parasitic worms 1-3% of leukocytes Elevated in parasitic worm infections and allergic reactions Basophils • • • • Deep blue granules in basic stain Releases heparin and histamine Less than 1% of leukocytes Similar to eosinophils in size, nucleus shape Monocytes • Largest of all blood cells • Spherical • Nucleus can be kidney-shaped, ovalular, or lobed • May leave bloodstream to become macrophages • 3-9% of leukocytes • Phagocytic Lymphocytes • Slightly larger than RBCs • Large, spherical nuclei surrounded by thin rim of cytoplasm • T cells and B cells – Immunity – (B cells produce antibodies) • 25-33% of leukocytes WBC Functions • Protect against infection • Squeeze between the cells of capillary wall and the space outside the blood vessel Connective tissue Blood capillary Leukocyte Splinter punctures 1 epidermis 2 Bacteria are introduced into the dermis 3 Bacteria multiply Injured cells release histamine, 4 causing blood vessels to dilate Epidermis Dermis Blood vessels 5 Neutrophils move through blood vessel walls and migrate toward bacteria 6 Neutrophils destroy bacteria by phagocytosis WBC Counts • Counts number of WBCs per cubic millimeter of blood • Typically 5,000 – 10,000 per cubic millimeter of blood • Leukopenia – low WBC count (<5,000) • Typhoid fever, flu, measles, mumps, chicken pox, AIDS • Leukocytosis – high WBC count (>10,000) • Acute infections, vigorous exercise, loss of body fluid • Differential WBC count • Lists percentages of each type of leukocyte • May change in particular diseases Blood Platelets • • • • • Platelets = thrombocytes Cell fragments of megakaryocytes Lack nucleus; half the size of a RBC 130,000-360,000 per cubic mm of blood Repair damaged blood vessels by sticking to broken surfaces Blood Plasma • • • • • Liquid portion of blood; straw-colored 55% of blood volume 92% water Transports nutrients, gases, vitamins Regulates fluid & electrolyte balance, maintains pH Plasma Proteins • The most abundant dissolved substances (solutes) in plasma Non-protein Substances • Gases, nutrients • Nitrogenous substances – Urea – product of protein catabolism (~50%) – Uric acid – product of nucleic acid catabolism – Amino acids – product of protein catabolism – Creatine – stores phosphates – Creatinine – product of creatine metabolism – BUN – blood urea nitrogen (kidney health indicator) Hemostasis • Stoppage of bleeding • Actions: – Blood vessel spasm (smooth muscle of vessel contracts) • Triggered by pain receptors, platelet release, or serotinin – Platelet plug formation (platelets adhere to surface) • Triggered by exposure of platelets to collagen – Blood coagulation • Causes formation of blood clot via a cascade of reactions • Triggered by cellular damage, blood contact with foreign substances Endothelial lining Collagen fiber Platelet Plug Formation 1 Break in vessel wall Platelet Red blood cell 2 Blood escaping through break 3 Platelets adhere to each other, to end of broken vessel, and to exposed collagen 4 Platelet plug helps control blood loss Extrinsic Clotting Mechanism • Chemical outside blood vessel triggers coagulation • Triggered when blood contacts a damaged blood vessel wall or tissues • Positive feedback mechanism Intrinsic Clotting Mechanism • Chemical inside blood triggers blood coagulation • Triggered when blood contacts a foreign substance Fate of Blood Clots • After a blood clot forms it retracts and pulls the edges of a broken blood vessel together while squeezing the fluid serum from the clot • Smooth muscle cells and fibroblasts stimulated to repair damaged blood vessel walls • Plasmin digests the blood clots • Thrombus = abnormal blood clot • Embolus = blood clot moving through the blood vessels Prevention of Coagulation • Smooth lining of blood vessels discourages accumulation of platelets & clotting factors • As clot forms fibrin absorbs thrombin, prevents clot from spreading • Anti-thrombin inactivates additional thrombin to block unnecessary clotting • Basophils and mast cells can secrete heparin (anti-coagulant) Arteriosclerosis/Atherosclerosis • Arteriosclerosis – Thickening and loss of elasticity in artery walls • Atherosclerosis – Specifically, fat plaques that are filled with cholesterol, other lipids, form in the artery Hypertension • Persistently elevated arterial pressure – High sodium intake, obesity, stress, arteriosclerosis – Left ventricle works harder to pump blood – The myocardium thickens – Coronary blood vessels cannot support this overgrowth, and heart muscle can die, replaced with fibrous tissue – Enlarged, weakened heart will eventually die • Also contributes to atherosclerosis – plaque can accumulate and cause coronary thrombosis or embolism, or stroke in the brain Blood Types – Terms to Know • Agglutination – clumping of RBCs in response to reaction between an antibody and antigen • Antigens – a chemical that stimulates cells to produce antibodies • Antibodies – a protein that reacts against a specific antigen ABO Blood Group • Type A, B, or O • Based on presence/absence of either of two major antigens on the RBC cell membrane: – Antigen A – Antigen B Red blood cell Red blood cell Anti-B antibody Antigen A Anti-A antibody Antigen B Type B blood Type A blood Red blood cell Anti-A antibody Anti-B antibody Antigen A Antigen B Red blood cell Type AB blood Type O blood Antigen A Red blood cell Anti-B antibody (a) Agglutinated red blood cells Anti-A antibody (b) Rh Blood Group • Rhesus monkey • Rh positive or negative – Presence/absence of “Antigen D” or other Rh antigens • Fetus can develop erythroblastosis fetalis (hemolytic disease) – Can happen in Rh-negative mother on the second or subsequent Rh-positive pregnancy