The Blood-Week 4.pdf - The Blood Whole blood is composed of ​formed elements​(cellular components and ​plasma​ a watery transport medium

The Blood-Week 4.pdf - The Blood Whole blood is composed of...

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The Blood Whole blood is composed of formed elements (cellular components) and plasma , a watery transport medium containing solutes (ions, glucose, waste material, electrolytes, and proteins). The proteins in plasma include the following: albumin —a water-soluble protein that plays a role in maintaining blood pH and osmotic pressure globulins —proteins that include the antibodies of the immune system and some blood-clotting factors fibrinogen —the precursor of fibrin , a blood-clotting protein Blood plasma with the clotting factors (such as fibrin) removed is known as serum . Simply stated, Blood = cells + plasma Plasma = blood – cells Serum = plasma – clotting factors Figure 3.1 shows the different components of blood and their relative percentages: Figure 3.1 Components of Blood Source: Frio 2007 Formed Elements of Blood (Cellular Components)
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The formed elements of blood consist of three cell structures: 1. red blood cells (erythrocytes) 2. white blood cells (leukocytes) 3. platelets Red Blood Cells Red blood cells (RBCs or erythrocytes) are biconcave cells with no nucleus; they live for about 120 days, and transport oxygen (O 2 ) and carbon dioxide (CO 2 ) to body cells. They are extremely flexible, squeezing through the thin capillaries and snapping back into shape when passing into the wider blood vessels. RBCs contain the four-subunit (heme) protein hemoglobin (Hb) . Each of the hemes encircles an iron (Fe) atom that binds to O 2 , making hemoglobin responsible for ninety-eight percent of the oxygen transported in the blood (Chiras 2005). Carbon monoxide (CO) has a much higher chemical affinity for iron than does oxygen; for this reason, it is lethal at high concentrations. In low-oxygen conditions, the kidneys secrete erythropoietin , a hormone that increases RBC production in the bone marrow. This is a homeostatic necessity in high altitudes, where oxygen is scarce ("thin air"). Athletes exploit this mechanism, training in elevated locales to force their bodies to produce more RBCs. This allows them to compete at higher endurance levels when back in a lower altitude. The liver and spleen destroy old RBCs. Focus on the Blood: Fifty-Six Facts Did you know that 1. there are one billion RBCs in two to three drops of blood? 2. blood makes up about seven percent of your body weight? 3. platelets support blood clotting, and blood donations give those with leukemia and other cancers a chance to live (America's Blood Centers 2007)? Click here to read the other fifty-three facts. White Blood Cells White blood cells (WBCs or leukocytes) are involved in the body's defense against disease-causing organisms. There are five types of WBCs: 1. neutrophils 2. eosinophils 3. basophils 4. monocytes 5. lymphocytes Neutrophils are approximately twice the size of RBCs. They live for six hours to a few days, and are the first cells to arrive at the site of an infection to phagocytize bacteria. Eosinophils are approximately the same size as neutrophils. They live for eight to twelve days, and they phagocytize antigen-antibody complexes and attack parasites.
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