Blood carries oxygen and nutrients to the tissues and organs and removes waste products. It is made up of several main components, including red blood cells, white blood cells, platelets, and plasma. Red blood cells carry and release oxygen throughout the body. White blood cells are part of your immune system and help fight infection. Platelets help the blood form clots, which stops bleeding.
Blood cells are suspended in a watery, yellowish liquid called plasma, which also contains proteins partly responsible for blood clotting and globulins that help fight infection and disease.
There are approximately 4 L to 5 L of blood in the body. Losing large amounts of blood quickly can lead to serious complications or death. Severe blood loss is usually treated with a transfusion or transfusion alternatives such as medications.