Chapter 39 Circulation

Chapter 39 Circulation - Chapter 39 Circulation I...

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Chapter 39 Circulation I. Circulatory System: An Overview A. A circulatory system is an internal transport system with three components: 1 Blood is a fluid tissue composed of water, solutes, and formed elements. 2 The heart is a muscular pump that generates pressure to keep the blood flowing. 3 Blood vessels are tubes of various diameters through which the blood is transported. B. There are two basic types of circulatory systems: 1 Arthropods and most molluscs have an open system: a. Blood is pumped from a heart into large tissue spaces where organs are “bathed.” b. Blood is returned to the heart at a leisurely rate. 2 Vertebrates have a closed system. a. All the vessels and the heart are connected so that blood remains enclosed. b. Blood volume is constant; rate slows as blood moves through the fine tubes of the capillary beds. C. Functional Links With the Lymphatic System 1 The lymphatic system is a network of vessels and organs that house vast numbers of infection-fighting cells. 2 The lymphatic system picks up excess fluids, solutes, and disease agents from the interstitial fluid. 3 This lymph is cleansed by exposure to the infection-fighting cells before being returned to the general circulation. II. Characteristics of Blood A. Functions of Blood 1 It carries oxygen and nutrients to cells, and it carries secretions and wastes away from them. 2 It contains phagocytic cells that fight infection. 3 It helps stabilize internal pH. 4 It equalizes body temperatures in birds and mammals. B. Blood Volume and Composition 1 An average-sized adult has a blood volume of about 5 quarts. 2 Plasma a. This fluid portion of the blood is mostly water. b. Some plasma proteins (alpha and beta globulins) transport lipids and vitamins; others function in immune responses (gamma globulins) and in blood clotting (fibrinogen). c. Plasma also contains ions, glucose, lipids, amino acids, vitamins, hormones, and dissolved gases. 3 Red Blood Cells (Erythrocytes) a. In mammals, red blood cells are biconcave disks that transport oxygen. b. Red blood cells contain hemoglobin, an iron-containing protein that binds with oxygen. c. They form in the red bone marrow from stem cells. d. When mature they have no nuclei; they live about 120 days. 1) Phagocytic cells remove the oldest cells from the bloodstream. 2) Cell count remains at 5.4 million/microliter for males and 4.8 for females. 3) When extra red blood cells are needed, the kidneys secrete an enzyme that converts a
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This note was uploaded on 01/04/2012 for the course BSC BSC1005 taught by Professor Orlando,rebecca during the Fall '10 term at Broward College.

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Chapter 39 Circulation - Chapter 39 Circulation I...

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