The compnents of blood and their function

Blood is made up of several different components each with a specific function. These components are:

Red Blood Cells (RBCs)

These give blood its colour. Their function is to transport oxygen throughout the body from the lungs and transport carbon dioxide back to the lungs so it can be exhaled.
The production of red blood cells is regulated by the kidneys. When the kidneys detect that there is a deficiency of red blood cells they release a hormone that stimulates the production of new red blood cells.
Red blood cells are produced within bone marrow.

White Blood Cells (leukocytes)

These are the cells that are responsible for fighting infection. Like red blood cells they are produced in the bone marrow. The body produces a substance known as colony stimulating factors, which encourage the production of white blood cells when they are needed.

Plasma

Plasma is the pale yellow liquid in which all blood cells are suspended. It contains red and white blood cells, antibodies and platelets. In addition to this it also contains proteins that help with clotting in order to seal blood vessels if they get cut.

Platelets

These are fragments of cells that work with the clotting proteins in the plasma to help stop bleeding.
Like red and white blood cells they are usually formed in bone marrow.


References:
American cancer society (2009), Blood and its components [on-line]
Available from: www.cancer.org/docroot/ETO/content/ETO_1_4x_Blood_And_Its_Compnents.asp