Blood is a special body fluid that circulates through your veins and arteries and has four main components: plasma, red blood cells, white blood cells and platelets.

What does Blood do?

  • Transports oxygen and nutrients to the lungs and tissues
  • Carries cells and antibodies to fight infection
  • Brings waste products to the kidneys and liver, which filter and clean the blood
  • Regulates body temperature
  • Forms blood clots to stop bleeding and allow for healing to occur.

What is in Blood?

Plasma: Plasma is the liquid part of blood. It has water, sugar, fat, protein, and salts. Plasma transports red and white blood cells, nutrients, waste products, antibodies, clotting factors and other clotting proteins, and chemical messengers (like hormones) throughout your body.

Red Blood Cells (RBCs): RBCs are also called erythrocytes. They are red and make up about 45% of your blood鈥檚 volume, which is why blood is red.聽RBCs are red because of a special protein called hemoglobin, which carries oxygen from your lungs to your body and returns carbon dioxide to your lungs to be exhaled.

White Blood Cells (WBCs): 聽WBCs are also called leukocytes. Their primary job is to protect your body from infection. They only make up about 1% of your blood volume. There are two types of WBCs: neutrophils (your immediate-response cells, which live less than a day) and lymphocytes (which can live in tissue indefinitely). The two main types of lymphocytes are T lymphocytes, which help regulate immune cell function and attack infected cells and tumors, and B lymphocytes, which make antibodies (proteins that attach to bacteria, viruses, and other foreign materials).

Platelets: Platelets, also called thrombocytes (thrombo [blood clot] + cyte [cell]), have no nucleus and are not actually cells. They are small fragments of cells. They are a component of blood whose function (along with clotting factors) is to stop bleeding by clumping and clotting blood vessel injuries. When functioning normally, they rush to the site of an injury and stick to where the blood vessel is broken to start forming a clot.

How Blood clots

The body initiates the clotting process when an injury to a blood vessel occurs. If you clot normally, your blood vessels will constrict at the injury site, and platelets will rush in and stick together to form a temporary plug. Next, clotting factors come in to form a fibrin clot that holds the platelets in place. Once that clot is formed, bleeding will stop, and healing can begin. Once the wound is healed, the clot dissolves.

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