life process Part 5 Blood and lymph, Excretion Inplants and animal

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Published on May 18, 2020 7:15:33 AM ● Video Link: https://www.youtube.com/watch?v=hs1XWXPj6iA

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Blood (1997)

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Blood Components


Normally, 7-8% of human body weight is from blood. In adults, this amounts to 4.5-6 quarts of blood. This essential fluid carries out the critical functions of transporting oxygen and nutrients to our cells and getting rid of carbon dioxide, ammonia, and other waste products. In addition, it plays a vital role in our immune system and in maintaining a relatively constant body temperature. Blood is a highly specialized tissue composed of more than 4,000 different kinds of components. Four of the most important ones are red cells, white cells, platelets, and plasma. All humans produce these blood components--there are no populational or regional differences.


Red Cells

microscopic photo of human erythrocytes
Human erythrocytes or "red cells"
(cell diameter about .0003 inches)
Red cells, or erythrocytes click this icon to hear the preceding term pronounced, are relatively large microscopic cells without nuclei. In this latter trait, they are similar to the primitive prokaryotic cells of bacteria. Red cells normally make up 40-50% of the total blood volume. They transport oxygen from the lungs to all of the living tissues of the body and carry away carbon dioxide. The red cells are produced continuously in our bone marrow from stem cells at a rate of about 2-3 million cells per second. Hemoglobin click this icon to hear the preceding term pronounced is the gas transporting protein molecule that makes up 95% of a red cell. Each red cell has about 270,000,000 iron-rich hemoglobin molecules. People who are anemic generally have a deficiency in red cells, and subsequently feel fatigued due to a shortage of oxygen. The red color of blood is primarily due to oxygenated red cells. Human fetal hemoglobin molecules differ from those produced by adults in the number of amino acid chains. Fetal hemoglobin has three chains, while adults produce only two. As a consequence, fetal hemoglobin molecules attract and transport relatively more oxygen to the cells of the body.


White Cells

White cells, or leukocytes click this icon to hear the preceding term pronounced, exist in variable numbers and types but make up a very small part of blood's volume--normally only about 1% in healthy people. Leukocytes are not limited to blood. They occur elsewhere in the body as well, most notably in the spleen, liver, and lymph glands. Most are produced in our bone marrow from the same kind of stem cells that produce red blood cells. Others are produced in the thymus gland, which is at the base of the neck. Some white cells (called lymphocytes click this icon to hear the preceding term pronounced) are the first responders for our immune system.
Platelets

electron microscopic photo of a human erythrocyte, a thrombocyte, and a leukocyte next to each other
erythrocyte (left), thrombocyte
(center), and leukocyte (right)
Platelets click this icon to hear the preceding term pronounced, or thrombocytes click this icon to hear the preceding term pronounced, are cell fragments without nuclei that work with blood clotting chemicals at the site of wounds. They do this by adhering to the walls of blood vessels, thereby plugging the rupture in the vascular wall. They also can release coagulating chemicals which cause clots to form in the blood that can plug up narrowed blood vessels. Thirteen different blood clotting factors, in addition to platelets, need to interact for clotting to occur. They do so in a cascading manner, one factor triggering another. Hemophiliacs lack the ability to produce either blood factor 8 or 9.

Platelets are not equally effective in clotting blood throughout the entire day.

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