What is Blood

Blood carries gases, nutrients and waste products through the body. Blood also fights infections, heals wounds and performs many other vital functions. There is no substitute for blood. It cannot be made or manufactured. Donors are the only source of blood for patients who need it.

One unit of blood can be separated into components: red blood cells, plasma, and platelets.

What is Blood?

Blood Cells Are Produced in Bone Marrow

Red cells, white cells and platelets are made in the marrow of bones, especially the vertebrae, ribs, hips, skull and sternum. These essential blood cells fight infection, carry oxygen and help control bleeding.

Plasma Carries Blood Cells

Plasma is a pale yellow mixture of water, proteins and salts. One of the functions of plasma is to act as a carrier for blood cells, nutrients, enzymes and hormones.

Blood Types Determine Donor-Recipient Matches

The approximate distribution of blood types in the U.S. population (distribution is different for specific racial and ethnic groups):

* In an emergency, anyone can receive type O red blood cells. People with type O blood are known as "universal donors."

** Type AB individuals can receive red blood cells of any ABO type. Those with type AB blood are known as "universal recipients." In addition, AB plasma donors can give to all blood types.