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Blood. Anatomy & Physiology. Functions of blood. Transportation Heat regulation. Composition of blood. Made of plasma & formed elements Plasma: fluid portion of blood Formed elements Red blood cells (erythrocytes) White blood cells (leukocytes) Platelets (thrombocytes).
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Blood Anatomy & Physiology
Functions of blood • Transportation • Heat regulation
Composition of blood • Made of plasma & formed elements • Plasma: fluid portion of blood • Formed elements • Red blood cells (erythrocytes) • White blood cells (leukocytes) • Platelets (thrombocytes)
Hematocrit or Packed Cell Volume (PCV) • Percent of red blood cells in whole blood • Buffy coat (less than 1%): white blood cells & platelets
Erythrocytes (RBCs) • Mature RBC has no nucleus, ribosomes, mitochondria • Small biconcave discs • Primary component: hemoglobin (1/3 of cell volume) • Flexible because of stretchable fibers called spectrin
Function of RBCs • Transportation of oxygen & carbon dioxide depends on hemoglobin & an enzyme carbonic anhydrase
Hemoglobin • 200-300 million molecules of hemoglobin in each RBC • Each hemoglobin molecule contains 4 protein chains called globin & each chain is bound to a red pigment, heme, which each heme contains an iron molecule • One hemoglobin molecule can unite with 4 oxygen molecules
Erythropoiesis • Formation of RBC • Begins in the bone marrow from hematopoietic stem cells which form all blood cells • In series of steps lose nuclei to become reticulocyte which is released into circulation which become mature RBC which is smaller
Erythropoietin • Hormone released by the kidney when blood oxygen levels decline which then stimulates the bone marrow to increase production of RBCs
Destruction of RBCs • Life span of RBC is about 105-120 days • Macrophages in lining of blood vessels in spleen & liver phagocytose old or damaged RBC • Hemoglobin broken down & amino acids, iron & pigment bilirubin released • Iron used to form new hemoglobin & bilirubin transported to liver & excreted into the intestines in bile
5 types All have nuclei Larger than RBCs Granulocytes (have large granules in cytoplasm) Neutrophils Eosinophils Basophils Agranulocytes Lymphocytes Monocytes Leukocytes (WBCs)
Neutrophils • About 65% of the total WBC count • Multilobed nucleus • Small light purple granules in cytoplasm • Function: cell defense by phagocytosis of microorganisms • Life span: hours to 3 days
Eosinophils • Usually 2 lobed nucleus • Large orange-red staining granules • Function: cellular defense usually against parasites & involved in allergic reactions • Life span: 10-12 days
Basophils • Usually 2 lobed nucleus • Sparse, large purple staining granules • Least numerous WBC • Function: secrete heparin & histamine • Life span: hours to 3 days
Lymphocytes • Smallest of WBC, about 25% of total WBC count • Large spherical nuclei with scant pale blue cytoplasm • T-lymphocytes: directly attack infected or cancerous cell • B-lymphocytes: produce antibodies against specific antigens • Life span: days to years
Monocytes • Largest of the WBC • Kidney bean shaped nuclei with large quantities of blue-gray cytoplasm • Phagocytic cell capable of ingesting bacteria, debris, cancerous cells • In tissue called macrophages • Life span: months
WBC Formation • Neutrophils, eosinophils, basophils originate in bone marrow • Most lymphocytes & monocytes originate in lymphatic tissue
Platelets • Small, nearly colorless, irregular • 3 important physical properties • Agglutination • Adhesiveness • Aggregation
Functions of platelets • Hemostasis: stoppage of blood flow • Damage to blood vesselsvascular spasm temporary platelet plug by sticky platelets secrete ADP, thromboxane & fatty acid (arachidonic acid) which are involved in coagulation • Coagulation: blood clotting
Formation & Life Span of Platelets • Formed in bone marrow, lungs & spleen by fragmentation of very large cell, megakaryocyte • Life span: 7 days
Blood Types • Refers to the type of antigens, called agglutinogens, present on RBC membrane • Important blood antigens: A, B, Rh • Agglutinins: antibodies dissolved in plasma that react with specific blood group antigens
ABO System • Type A: Antigen A on RBCs • Type B: Antigen B on RBCs • Type AB: Antigen A & B on RBCs • Type O: Neither A nor B on RBCs • Plasma never contains Ab against Ag present on it own RBCs • Plasma does contain AB against those Ag not present on its RBCs
The Rh System • Rh positive: Rh antigen is present on RBCs • Rh negative: RBCs have no Rh antigen • Blood does not normally contain anti-Rh antibodies except thru previous transfusion or pregnancy
Blood Plasma • 90% water, 10 % solutes • Most of the solutes are proteins (formed by liver) • Albumin: help maintain osmotic balance • Globulins: immune mechanism • Fibrinogen: blood clotting • Remaining solutes are food substances, metabolic products, respiratory gases, hormones, etc
Four components critical to coagulation Prothrombin Thrombin Fibrinogen Fibrin Three stages Stage I Stage II Stage III Coagulation
Stage I • Production of thromboplastin activator by either: • Extrinsic pathway: chemicals released from damaged tissues • Intrinsic pathway: chemicals present in the blood
Stage II • Conversion of prothrombin to thrombin by the prothrombin activator produced in stage I
Stage III • Conversion of fibrinogen to fibrin and production of fibrin clot by thrombin produced in Stage II
Coagulation facts • Many of clotting factors require calcium ion as a cofactor • Liver synthesizes both prothrombin & fibrinogen. Vitamin K is necessary for production of prothrombin
Conditions that oppose clotting • Smooth surface of lining of blood vessels does not allow platelets to stick • Antithrombins: substances in blood that oppose or inactivate thrombin • Ex: Heparin
Conditions that hasten clotting • Rough spot in the blood vessel lining • Abnormally slow blood flow
Clot Dissolution • Fibrinolysis: physiologic mechanism that dissolves clots
Image Citations • Slide 5: Hematocrit, 12/20/06, http://www.drstandley.com/labvalues_hematology.shtml • Slide 13: Neutrophil, 12/27/06, http://faculty.une.edu/com/abell/histo/histolab3a.htm • Slide 14: Eosinophil, 12/27/06, http://faculty.une.edu/com/abell/histo/histolab3a.htm • Slide 14: eosinophil1a, 12/27/06, http://cellbio.utmb.edu/microanatomy/blood/more_eosinophils.htm • Slide 15: Basophils, 12/27/06, http://faculty.une.edu/com/abell/histo/histolab3a.htm • Slide 16: Medium lymphocyte, 12/27/06, http://www.anatomy.dal.ca/Human_Histology/Lab7/61LO4.html • Slide 17: Monocyte, 12/27/06, http://www.med-ed.virginia.edu/courses/path/innes/nh/wcbmaturation.cfm • Slide 21: Megakaryocyte, 12/30/06, http://www.med-ed.virginia.edu/courses/path/innes/nh/platelets.cfm