red and white human blood cells as seen under a microscope using a blue slide stain

A blood cell (also called blood corpuscle) is any cell of any type normally found in blood. In mammals, these fall into three general categories:

• red blood cells — Erythrocytes
• white blood cells — Leukocytes
• platelets — Thrombocytes

Together, these three kinds of blood cells sum up for a total 45% of blood tissue by volume (55% is plasma).^[1] This is called the hematocrit and can be determined by centrifuge or flow cytometry.

[edit] Types

[edit] Red blood cells

Red blood cells are primarily for carrying oxygen and some carbon dioxide through the use of hemoglobin and have a lifetime of 120 days.

[edit] White blood cells

White blood cells are part of the innate immune system and have a lifetime of a few days to years.

[edit] Platelets

Platelets are involved in blood coagulation and have a lifetime of about 9 days ^[2].

[edit] Disorders

There are several conditions that affect red blood cells, and one that affects white blood cells.

One condition, anemia, occurs when the number of red blood cells is lower than normal. An opposite conditions, known as polycythemia occurs when the number of red blood cells is greater than normal.

Acquired Immune Deficiency Syndrome (AIDS) occurs when a white blood cell mistakenly grants permission to harmful bacteria and viruses to enter the bloodstream.

Sickle-Cell Disease occurs when red blood cells, which normally look like glazed doughnuts, take on the form of sickles. This condition prevents the infected cells from carrying as much oxygen.

[edit] References

[edit] External links

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Learning resources from Wikiversity

• What is Blood? from the Genetic Science Learning Center at the University of Utah.
• Cells of the blood

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