 Blood is the fluid that circulates in the arteries and veins of your body. Your body uses it to carry oxygen to the cells through the arteries. Blood is bright red when it has oxygen in it, which it gets from the lungs. After it gives the oxygen to the body's cells, it becomes bluish red, and heads back to the heart through the veins, full of carbon dioxide and other waste products. It will then be sent to places where the waste can be disposed of ... the liver, kidneys and other organs will get rid of poisons, and the lungs will take out the carbon dioxide. Blood is actually a mixture of many things. First, the liquid part is a yellowish fluid, called plasma. In this fluid are suspended cells that make up about 45 percent of the volume of whole blood These include red blood cells (erythrocytes), white blood cells (leukocytes) , platelets (thrombocytes), as well as other salts and organic substances in solution. In an average healthy adult, the volume of blood represents just under a tenth of the body weight, or about 5 litres.
 Plasma is the yellowish clear liquid that carries all the cells. Its main component is water. It also contains proteins, (like fibrinogen and prothrombin, which help with in clotting), inorganic elements and compounds such as sodium, potassium, calcium chloride, carbonate, and bicarbonate, as well as sugar, hormones, enzymes, fats, amino acids, and waste products such as urea. These various components of plasma are made in the liver, endocrine glands, and the lymphocytes. All these substances occur in tiny quantities, but there are a lot of them. Blood Types In the early 20th century, doctors discovered that blood transfusions often failed because the blood type of the recipient was not the same as that of the donor. The four blood types are now known as A, B, AB, and O. Some of the different blood type cells carry antibodies which will kill other blood cells, so if the types are mixed, the blood cells destroy each other. Blood transfusions from a donor need to be the same type of blood as the recipient has. Type O cells, however, don't have these antibodies, and so can usually be given to anyone. Type O is called 'universal donor' blood. Type AB blood has no antibodies and can receive any of the four types of blood. Type AB is called 'universal recipient' blood. Another blood component called the Rh factor also has an effect on which blood types can be given, particularly newborn babies. |
