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Blood & Blood Vessels Anatomy & Physiology/Cardiovascular System
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Functions of Blood Blood transports everything that must be carried from one place to another within the body. For example: Nutrients Waste Body Heat Oxygen Carbon Dioxide
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Functions of Blood In order to transport these things, blood flows through a vast and complex system of closed tubes called blood vessels. Types of blood vessels include: Arteries- large, thick vessels that carry oxygen and nutrient rich blood from heart/lungs to the body Veins- large, but thinner vessels that carry oxygen and nutrient depleted blood from the body to the heart/lungs Capillaries- small, very thin vessels that form woven networks of arterioles and venules (mini arteries and veins) and where a direct exchange occurs between blood and body tissue cells.
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Composition of Blood Blood is unique in that it is the only fluid body tissue. Blood is a connective tissue composed of solid elements suspended in a fluid called plasma. About 55% of blood is made up of plasma, with the remaining 45% made up of the solid elements.
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Solid Elements of Blood Erythrocytes- red blood cells that function in oxygen transport and make up the large majority of the solid matter of the blood. The mass of erythrocytes in a blood sample is also referred to as the hemocrit. Leukocytes- white blood cells that function as part of the body’s defense system. Platlets- Cell fragments that function in blood clotting.
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Plasma Over 90% of plasma is water. However, dissolved in the plasma are many important elements being transported by the blood. When placed in a centrifuge and spun at high speed, plasma rises to the top of any blood sample.
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Composition of Erythrocytes Erythrocytes, also known as red blood cells, are unusual cells because they do not contain a nucleus or mitochondria. The lack of mitochondria means that they do not require oxygen and therefore do not use up any of the oxygen that they transport throughout the body. Erythrocytes ultimately are sacs of an oxygen binding protein called hemoglobin.
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Hemoglobin Hemoglobin is an oxygen binding protein. Hemoglobin contains iron, which is what gives red blood cells their color. The more hemoglobin molecules a red blood cell contains, the more oxygen the cell is able to carry. The amount of hemoglobin produced by the body can vary dependent on elevation and physical training.
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Composition of Leukocytes Leukocytes, also known as white blood cells, do contain nuclei and the usual organelles of a cell. White blood cells have the unique ability to slip in and out of blood cells and in this way can move throughout the body, depending on where they are needed. When white blood cells are needed to defend against a foreign agent, the body speeds up their production.
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Hematopoiesis Hematopoiesis is the process of blood cell formation, which occurs in red bone marrow. The rate of red blood cell formation is controlled by a hormone called erythropoietin. The rate of white blood cell formation is controlled by hormones called colony stimulating factors. The rate of platelet production is controlled by hormones called interleukins.
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Hemostasis Hemostasis is the process that results in blood clotting when the wall of a blood vessel breaks. This process involves three main stages: 1.Platelet plug forms: The platelets become sticky and cling to the damaged site. 2.Vascular spasms occur: Platelets release serotonin causing the blood vessel to spasm and narrow. 3.Coagulation events occur: After time, the clot retracts from the damaged site and releases serum which pulls together the ruptured ends of the blood vessel.
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Hemostasis Video http://health.howstuffworks.com/adam- 200077.htm
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