Lecture 15 BIO 311D 1st Edition Outline of Last Lecture I Circulatory System II Gastrovascular Cavities III Evolutionary Variation in Circulatory Systems IV Open and Closed Circulatory Systems V Organization of Vertebrae Circulatory Systems VI The Heart Outline of Current Lecture I Fluid Return by the Lymphatic System II Blood Components III Plasma IV Erythrocytes V Leukocytes VI Stem Cells Current Lecture Fluid Return by the Lymphatic System The lymphatic system returns fluid that leaks out from the capillary beds Fluid called lymph reenters the circulation directly at the venous end of the capillary bed and indirectly through the lymphatic system The lymphatic system drains into veins in the neck Valves in lymph vessels prevent the backflow of fluid Lymph nodes are organs that filter lymph and play an important role in the body s defense Edema is swelling caused by disruptions in the flow of lymph Blood components contribute to exchange transport and defense With open circulation the fluid that is pumped comes into direct contact with all cells The closed circulatory systems of vertebrates contain blood a specialized connective tissue Blood consists of several kinds of cells suspended in a liquid matrix called plasma The cellular elements occupy about 45 of the volume of blood Plasma Blood plasma is about 90 water Among its solutes are inorganic salts in the form of dissolved ions sometimes called electrolytes Another important class of solutes is the plasma proteins which influence blood pH osmotic pressure and viscosity Various plasma proteins function in lipid transport immunity and blood clotting Cellular Elements Suspended in blood plasma are two types of cells Red blood cells erythrocytes transport oxygen O2 White blood cells leukocytes function in defense Platelets a third cellular element are fragments of cells that are involved in clotting Erythrocytes Red blood cells or erythrocytes are by far the most numerous blood cells They contain hemoglobin the iron containing protein that transports O2 Each molecule of hemoglobin binds up to four molecules of O2 In mammals mature erythrocytes lack nuclei and mitochondria Sickle cell disease is caused by abnormal hemoglobin proteins that form aggregates The aggregates can deform an erythrocyte into a sickle shape Sickled cells can rupture or block blood vessels Leukocytes There are five major types of white blood cells or leukocytes monocytes neutrophils basophils eosinophils and lymphocytes They function in defense by phagocytizing bacteria and debris or by producing antibodies They are found both in and outside of the circulatory system Platelets Blood Clotting Platelets are fragments of cells and function in blood clotting Coagulation is the formation of a solid clot from liquid blood A cascade of complex reactions converts inactive fibrinogen to fibrin forming a clot A blood clot formed within a blood vessel is called a thrombus and can block blood flow Which of the following is a type of leukocyte A Basophil B Eosinophil C Monocyte D All of the above E None of the above Stem Cells and the Replacement of Cellular Elements The cellular elements of blood wear out and are being replaced constantly Erythrocytes leukocytes and platelets all develop from a common source of stem cells in the red marrow of bones especially ribs vertebrae sternum and pelvis The hormone erythropoietin EPO stimulates erythrocyte production when O2 delivery is low
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