Blood travels through your entire cardiovascular system. Blood is actually a tissue that is made up of red blood cells, white blood cells, plasma, platelets, and other components. The blood delivers oxygen and nutrients to the rest of the body and removes carbon dioxide and waste products from the body.
The average person has about 1 gallon to 1½ gallons (4 to 6 liters) of blood circulating in his or her body. And your heart pumps the whole blood volume every minute. That is to say that five liters of blood flows though your heart every minute.
Blood is made up of four parts:
- Red blood cells, to carry oxygen (and they give blood its red color)
- White blood cells, to fight infection
- Platelets, to help cuts, scrapes and wounds clot
- Plasma, the liquid part of blood to transport nutrients, proteins and hormones throughout the body.
Your healthy body is constantly replenishing each of these blood components. Some are able to be replenished within a few hours, some within a few weeks.
While everybody’s blood is red, not everybody has the same type of blood. There are eight blood types, including:
The letters indicate specific types of proteins found on the red blood cells. The positive or negative indicates whether you have the “Rh” protein in your blood (positive) or not (negative). “O positive” is the most common blood type.
No one blood type is better for your health than another. But mixing blood types would make you very sick. So, if you need a blood transfusion, it is important to receive the same type of blood you have or “O negative” blood. Blood is carefully “cross-matched” between the donor and recipient before a transfusion is given. All blood types can receive “O negative” blood in a transfusion. This is because it lacks specific proteins that would be harmful to people whose blood type differed. This is the reason you may have heard it said that if you have “O negative” blood, you are considered a “universal donor.”
Oxygen and Nutrient Delivery
One of the most important functions of blood is the transportation of oxygen and nutrients to all tissues of the body. Arteries, arterioles, and capillaries deliver oxygen, nutrients, hormones, and proteins to all tissues of the body.
As your blood travels through your body, it undergoes another important process: waste filtration. When blood leaves the body's tissues to travel back to the heart and lungs, veins carry excess nutrients and other items (carbon dioxide, urea, and lactic acid, for example) that your body cannot use. Then your lungs, kidneys, and liver filter the waste products out of your blood.
Your blood’s white blood cells are important for detecting and fighting infections within your body.
Blood Clotting and Wound Healing
Your blood’s platelets are important for quickly repairing wounds to prevent blood loss and seal the skin as a barrier to infection. The platelets attach themselves to the cut or wound. There are several processes that happen simultaneously to attract other platelets to attach to the wound, and produce proteins from the blood’s serum that create a network over the wound. Together the platelets and this network create an effective mesh that is the clot that gets the bleeding to stop.
Regulation of Body Systems
Your blood also plays an important part in regulating temperature, acid-base (pH) and electrolyte (for example, sodium and potassium) balance within your body.