2010 BLOOD & HEMATOPOIESIS Complete +lab


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HEMATOPOIETIC SYSTEM I: PERIPHERAL BLOOD Margaret Uthman, MD Reading: Gartner and Hiatt, pages 89-101; Klein and McKenzie, pp155-181 Learning Objectives: 1. Describe the composition of normal peripheral blood, including the relative quantities of the blood cells. 2. Identify normal peripheral blood cells. 3. Describe the function and "life cycle" of normal peripheral blood cells. Key Words : Erythrocytes, reticulocytes, neutrophils, eosinophils, basophils, monocytes, lymphocytes and platelets I. Composition. Blood is a fluid connective tissue constituting about 7% of our total body weight (about 5 liters in the human). The primary components are: A. Plasma : The liquid in which peripheral blood cells are suspended. Composed of water, electrolytes such as Na + and Cl, (0.9%), 7% plasma proteins (such as albumin, fibrinogen, globulins), hormones, fats, amino acids, vitamins carbohydrates, lipoproteins as well as other substances. The normal plasma volume is 40 ml/kg of body weight. B. Formed Elements (blood cells): 1. Erythrocytes (red blood cells or rbc): occupy about 40-45% of the total blood volume or 30 ml/kg body weight. 2. Leukocytes (white blood cells or wbc) and Platelets: together make up about 1-2% of the total blood volume. Freshly drawn blood is a red fluid (specific gravity of 1.052-1.064). It forms a jelly-like mass if allowed to clot. The clot is formed by the conversion of fibrinogen to fibrin which forms a meshwork that entraps the formed elements. If the gel is centrifuged, cell free serum can be obtained. If an anticoagulant is added, blood can be sedimented into three distinct layers due to different densities of elements: rbc > wbc > plasma. The lowermost layer (45% of the blood volume) consists of erythrocytes. Above this region is a grayish white layer (buffy coat) which represents the platelets, lymphocytes and granulocytes (about 1-2% volume). Plasma is the top layer. II. Morphology and Function of the Blood Cells A. Erythrocytes (mature red blood cells) 1. Cytology The mature human erythrocyte measures about 7-8 μ m in diameter and appears as an anucleate, acidophilic cell. In addition to the nucleus, the mature erythrocyte also loses its Golgi
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apparatus, centrioles, ER and most of its mitochondria. a. Bulk of the cytoplasm (90-95% of dry weight) consists of the iron-carrying pigment hemoglobin . Few organelles present. β b. Shape A biconcave disk to achieve a maximum surface area to cytoplasmic volume ratio. The surface area of an erythrocyte is calculated to be 128 μ m 2 . Thus, the average person has 3840 m 2 of rbc membrane area for respiratory exchange. The cell is enclosed in a typical fluid, bilayered cell membrane which is flexible and elastic enough to allow the cell to move through capillaries. Cells frequently assume a cup shape in capillaries. Peripheral membrane proteins, spectrin and actin, serve a cytoskeletal function. Peripheral blood: red blood cells (air dried, Wright stain)
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This note was uploaded on 12/25/2010 for the course MSI 1 taught by Professor Rogerj.bick during the Spring '10 term at University of Texas Health Science Center at San Antonio.

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