Chapter 15 Cardiovascular System Blood Summary We have examined the mechanisms by which the heart pumps blood to 8ssues at a su cient rate We then described how this ow of blood could be regulated to distribute more to the 8ssues that need it by varying the resistance of blood vessels In this lecture we examine the blood itself to see why it is so cri8cal that our cell receive su cient blood ow Components of Blood What are some of the components of blood Proteins Albumin Globulins Fibrogen Electrolytes Gases Oxygen and CO2 Urea Uric Acid Crea8ne Erythrocytes Leukocytes Platelets What happens when you go to the doctor they take blood and do a work up The Hematocrit Because erythrocytes are denser they are pulled to the bo9om of the tube hematocrit Plasma the least dense component remains at the top Between these two layers rests a thin layer of leukocytes and platelets The hematocrit is a useful clinical measure because it indicates whether a person has a normal complement of erythrocytes Components of Plasma Plasma is an aqueous solu8on in which a great variety of solutes are dissolved Although proteins are the most abundant solutes by weights the smaller solutes are generally present in higher concentra8ons The composi8on of plasma is very similar to that of inters88al uid The Bends As a diver goes deeper the increased pressure causes an increase in the concentra8on of gases in the blood especially nitrogen according to c kP If the diver comes to the surface too quickly nitrogen gas bubbles form in the blood as the pressure decreases The bubbles can oWen lodge in the joints and also clog blood vessels and causes paralysis and even death Erythrocytes Red blood cells are the most abundant cells in the blood 5 million per mm3 Shaped like disks and lack nuclei mitochondria and other organelles They transport oxygen and carbon dioxide in the blood for exchange with the body cells and lung 8ssue Oxygen and Carbon Dioxide Transport Erythrocytes have a high capacity for carrying these gases because they contain in their cytoplasm two proteins Anemia Sickle cell anemia is a hereditary disease caused by a muta8on in the gene that codes form hemoglobin This single amino acid subs8tu8on causes the hemoglobin molecules to ploymerize link to one another when oxygen levels are low making the erythrocyte sickle shaped and Life Cycle of Erythrocytes 1 3 2 Leukocytes Leukocytes Are nucleated and contain all the machinery making them the only fully func8onal cells in the blood Leukocytes are found not only in the blood but outside the vessels in the 8ssues of the body by squeezing through pores in capillaries This ability to migrate is essen8al to their func8on which is to defend the body against invading microorganisms and foreign materials Blood Platelets Platelets are colorless cell fragments that come from por8ons of bone marrow cells that break o They are smaller than erythrocytes and contain mitochondria smooth ER but no nucleus Are important in triggering the sequence of events that leads to the forma8on of blood clots Platelet Plug Blood vessel damage exposes the endothelium protein called vWf binds to collagen triggering the binding of platelets to vWf This binding triggers the metabolism and surface proteins making the platelets sCcky They also are triggered to release epinephrine which causes vasoconstric8on and ADP which causes the platelets to aggregate into a mess Platelet Plug However platelet plug forma8on is limited to the area of blood vessel damage to prevent unnecessary blood clots Under normal condi8ons endothelial cells secrete nitric oxide NO and release prostacyclin both of which inhibits platelet aggrega8on Forma8on of a Blood Clot Barber Surgeons Barbers Pole Leeches and Bloodlebng Leeches are known for their ability to suck blood They are currently used to increase blood ow to speci c areas of the body in treatments of ischemia pain and in amma8on Its saliva contains an anesthe8c a vasodilator and an an8coagulant
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