Blood - Research Article from Macmillan Science Library: Animal Sciences

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Blood Composition

The blood of mammals—including humans—is complex. About half of the volume of blood is made up of blood cells, which originate in the bone marrow. Blood cells begin as stem cells, then develop into many other kinds of cells—red cells, white cells, and platelets. Blood is composed of 55 percent plasma and 45 percent other elements.

Plasma is the watery part of the blood. Plasma is 90 percent water and carries most of the chemicals in the blood. These chemicals include minerals such as sodium, potassium, vitamins, hormones, enzymes, and glucose. Some of these substances are manufactured in the body; others enter through the lungs or with food. Plasma also carries dissolved gasses, especially oxygen, carbon dioxide, and nitrogen.

Blood's red color, seen in the mosquito's Blood's red color, seen in the mosquito's "sac," arises from its oxyhemoglobin.

Most stem cells become red blood cells, or erythrocytes. Human blood contains 4.8 to...

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This section contains 1,178 words
(approx. 4 pages at 300 words per page)
Buy the Blood Encyclopedia Article
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Macmillan Science Library: Animal Sciences
Blood from Macmillan Science Library: Animal Sciences. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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