Physical Fitness and Well-Being Blood Part 1
About physical fitness, medical information, trivia, anatomy, well-being and care of your blood and plasma.
TAKING A PHYSICAL--HEAD TO TOE
If you're an average-sized adult, you have just a little over five quarts of blood in your body.
Pumped by your heart, your blood moves out through a complex system of blood vessels. The largest of these, the aorta, is about 1 in. in diameter, while the smallest is only about 1/2500 in. in diameter. There are over 60,000 mi. of these vessels carrying blood through your body.
Blood serves four basic functions: nutritive, by carrying food to each tissue cell; respiratory, by carrying oxygen from the lungs to the cells and by carrying CO2 from the cells to the lungs; protective, by carrying disease-killing substances to all parts of the body; and regulatory, by carrying hormones and other chemicals which cause the distribution of blood to change, temperatures to change, water levels to remain balanced, etc.
Blood is 55% liquid and 45% solids. Red blood cells, white blood cells, and platelets make up the solid portion.
Red blood cells are the most abundant. They are saucer-shaped and about 1/3500 in. in diameter, and you have about 25 trillion of them. Fastened end to end, they would form a string which you could wrap around the world nearly three times.
Red blood cells have a life span of about three months. As they die, they are replaced by new cells produced in the marrow of your bones.
The principal bones where red blood cells are manufactured are in the upper legs, pelvis, sternum, ribs, vertebrae, upper arms, and skull.
Born in the bones, the red blood cells mature quickly and enter the circulating blood through vessels running through your bone marrow.
Red blood cells more than 120 days old are removed from circulation by your spleen, an organ located in the upper-left-hand portion of your abdomen.
Red blood cells absorb oxygen as they move through vessels in your lungs. Then, as they circulate through your body, they release this oxygen. Each cell throughout your body uses this oxygen to produce energy from the simple sugars, or glycogen, which your body has manufactured from the foods you eat.
The life processes of each cell in your body include both eating and excretory functions. Just as each cell burns glycogen and oxygen for energy, so does it excrete acids and carbon dioxide. The same red blood cells which carried oxygen to the cells now absorb these acids and carbon dioxide and carry them off to be released from your body via your lungs and kidneys.
Depending on their type, most white blood cells are produced either in your marrow or in the lymph nodes, spleen, thymus, tonsils, and lymph tissue of your digestive system.
White blood cells can move throughout your body under their own power.
One type of white blood cell can surround and eat up bacteria and other foreign substances which enter your body. This renders these substances harmless.
A second type of white blood cell is more complex. Called a lymphocyte, it plays a major role in your body's ability to become immune to certain diseases. Each cell is like a microscopic computer and chemistry lab, analyzing harmful substances and synthesizing chemicals to destroy them.
Platelets are the smallest cells that make up your blood. When injury occurs, they release a chemical which causes blood clotting and promotes eventual healing of the injured area.
Plasma is the liquid portion of your blood. In addition to supplying the vehicle for circulating blood cells through your body, plasma contains proteins, water, and electrolytes. The electrolytes--sodium, potassium, etc.--convey electrical impulses throughout your body, affecting all the vital functions and aiding in such things as communication between your brain and other organs.
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