Blood How it works on body care?

BLOOD

Blood, the body's transport medium, consists of about equal parts of a watery fluid called plasma and a mixture of red cells, white cells, and platelets. The red cells give blood its color and there are some 25 trillion of them. Each lasts about four months, wearing out and breaking up. And new cells to replace the old are produced in the bone marrow at a rate of about one million a second. The red color of the cells comes from hemoglobin, a combination of protein and an iron pigment. It is the hemoglobin that actually carries oxygen from the lungs to the capillaries and then carries carbon dioxide to the lungs, where it is exhaled.

Hemoglobin is a substance with an ability to hold very large quantities of oxygen. If it didn't exist, and if oxygen had to be dissolved in blood plasma, the body would require 300 quarts of blood instead of 5. White cells are less numerous than red but still there are 20 to 50 billion of them. Typically, in a pinprick of blood there may be some 10,000 white cells and as many as 5 million red cells. There are several kinds of white cells. One type, the granular leukocyte, is produced in the bone marrow along with red cells. Another, the lymphocyte, is produced in the lymph nodes, tonsils, and adenoids. White cells have an important role in the body's defense against invasive bacteria. Unlike the red cells, the white ones can move. They usually move along the sides of blood vessels rather than being pushed along with the red cells in the middle. They move by pushing out part of themselves ahead, then sliding the rest into the advanced area.

They can flow around and engulf bacteria. The battle, however, is not all one-sided. White cells can be destroyed by bacterial poisons, and pus is an accumulation of dead white cells and bacteria. But while bacteria sometimes can overwhelm the white cells, much more often the outcome is the other way, and most bacterial invasions (and they occur almost constantly) are repulsed. The blood platelets, which are smaller than the red cells, help blood to coagulate or clot. They collect at the site where a blood vessel is cut or otherwise injured, and they produce tiny fibrin threads, which lead to clot formation, helping to minimize blood loss. Plasma, which constitutes about half of whole blood, and is the part without cells, is itself about 91 percent water.

The remainder is made up of such minerals as sodium, calcium, potassium, and phosphorus, plus fats, sugars, plasma proteins, and antibodies. Antibodies are another part of the body's defense mechanism. Micro- organisms entering the body stimulate the production of antibodies which then, in very specific fashion, lock on to and incapacitate them. And it is by causing the body to produce antibodies specific against a particular disease organism that vaccines work. After use of a vaccine, the antibodies are in the plasma, ready and waiting to attack immediately if the disease organism should appear.