Blood contains four main components:
- Red Cells - that help carry oxygen to tissues
- White Cells - that help the body fight disease and infection
- Platelets - that help prevent bleeding
- Plasma - that carries proteins and other clotting factors.
There are four major blood types: "O", "A", "B", and "AB". Also, a certain substance, the "Rh- factor, is either present on the red cells or absent.
Approximately 85% of the population has "Rh" factor on their red cells. These people are categorized as "Rh" positive. About 15% of the population lack the "Rh" factor making them "Rh" negative. The blood type breakdown in the United States is as follows:
|Blood Type||Number of People||% of Population|
|O pos||1 in 3||37.4%|
|O neg||1 in 15||6.6%|
|A pos||1 in 3||35.7%|
|A neg||1 in 16||6.3%|
|B pos||1 in 12||8.5%|
|B neg||1 in 67||1.5%|
|AB pos||1 in 29||3.4%|
|AB neg||1 in 167||0.6%|
The rarest type of blood is the type that is not available when a patient needs it.
It takes 24 to 72 hours to type and test blood after a donation and BEFORE it can be used for patient.
In a crisis, the blood that saves lives is the blood that was donated BEFORE the crisis!
How Much Blood Does a Person Have?
- A unit of blood is equal to one pint or two cups.
- For every 25 lbs. of body weight, you have two pints.
- A person weighing 125 lbs. has 10 pints of blood in circulation.
- A person weighing 150 lbs. has 12 pints of blood.