Human Blood
...in the red cells to be hemoglobin, a protein that contains iron. Hemoglobin combined with oxygen gives the blood its characteristic red color. Therefore, the blood that goes from the lungs is a bright red because it carries a great amount of oxygen; in contrast, the blood that returns to the lungs is a much darker red, since it has given up much of it’s oxygen to the tissues. B. Leukocytes: white blood cells which protect against infection. The leukocytes are very different from the erythrocytes in appearance, quantity, and function. They contain nuclei of varying shapes and sizes; the cells themselves are round. They are also out numbered by the red blood cells. The different types of white blood cells are identified by their size, the shape of the nucleus, and the appearance of granules in the cytoplasm when cells are stained, usually with Wright’s blood stain. Granulocytes include neutrophils, which show lavender granules; eosinophils and monocytes. The ratio of different types of leukocytes is often a valuable clue in arriving at a diagnosis. The most important function of leukocytes is to destroy pathogens. Neutrophils approximately 70% of are circulating neutrophils. Their cytoplasm is packed with pale, neutral-staining granules containing lissome enzymes and bactericidal compounds. Neutrophils are highly mobile and are usualy the first of the WBCs to arrive at an injury site. Eosinophils are also called acidophilus because of their granules stain oerosin, an acidic red dye. Eosinophils are similar in size to neutrophils and represent 2-4 % of the circulating Webs. These cells have both deep and bilobed nucleus, making an eosinophils relatively easy to identify. Eosinophil numbers increase dramatically during an allergic reaction or a parasitic infection. Basophils are so named because they have numerous granules that stain with basic dyes. These inclusions stain a deep purple with the stains used in standard blood smear. Basophils are relatively rare, accounting for less than 1% of the leukocyte population. Monocytes are the largest WBC. They are 2-3 times larger in diameter of the typical RBC. These cells account for 2-8% of the WBC population. Monocytes circulate for just a few days before entering peripheral tissues. Outside the blood stream , monocytes are called free macrophages, to distinguish them from the immobile macrophages. Minocytes are one component of monocytes-macrophage system that includes related cell types, such as fixed macrophaged and more specialized cells such as the microglia of the CNS. Lymphocytes are usually slightly larger staining nucleus than RBCs and account for 20-30% of the WBC population. Blood lymphocytes represent a minute segment of the entire lymphocyte population, of the lymphatic system and are connected to the cardiovascular system. C. Platelets: cell fragments that participate in blood clotting. Of all the elements formed in the blood platelets (thrombocytes) are the smallest. These tiny structures are not cells in themselves, but fragment of cells. The number of platelets in the circulating blood has been estimated at 2000,000 to 400,000 per cubic millimeter. Platelets are essential to blood coagulation (clotting). When as a result in injury, blood comes in contact with tiny tissue other than the lining of the blood vessels, the platelets stick together and form a plug that seals the wound. They then release chemicals that take part in a series of reactions that eventually results in the formation of a clot. The last step in these reactions is the conversion of a plasma protein called fibrinogen into solid threads of fibrin, which form the blood clot. IV. Blood Plasma Over half of the total volume of blood in the body is plasma. The plasma itself is 90% water. Many different substances, dissolved or suspended in water , make up the other 10%. The plasma content varies somewhat, since the substances carried by blood to and from the organs get used and added to. The body tends to maintain a fairly constant level of these substances. For example the level of glucose, a simple sugar, is maintained at a remarkably constant level of about one tenth of a 1% solution. A. Albumins, the most abundant protein in the plasma, are important for maintaining the osmotic pressure of the blood. This protein is manufactured in the liver. The antibodies combat infection and the blood clotting factors are also manufactured in the liver. B. Globulins, account for approximately 35% of the plasma protein population. Fibrinogen, accounts for about 4% of the plasma...