Blood is the component of the circulatory system that is responsible for carrying oxygen and nutrients to tissues and cells, removing waste and fighting infection. Blood is a tissue and is made up of 80 percent liquid and 20 percent solid, according to the Texas Heart Institute. Blood is made mostly of plasma, but also contains red blood cells, white blood cells and platelets.
Functions
Different components of the blood are responsible for carrying out separate body functions. Blood is responsible for carrying oxygen and nutrients from the digestive tract to the body’s cells, as well as picking up waste and carbon dioxide and carrying them to the kidneys for filtration, according to the Texas Heart Institute. Blood also helps regulate body temperature, carries hormones to the cells of the body, signals antibodies that fight infection and provides material for clotting, which helps wounds and tissue to heal.
Blood Cells
Blood cells come in three types: red blood cells, white blood cells and platelets, which are actually cell fragments. Red blood cells, or erythrocytes, are responsible for carrying oxygen and nutrients to tissues. Hemoglobin is the protein component of red blood cells, where oxygen binds and is carried through blood vessels. Red blood cells also remove carbon dioxide from the tissues. White blood cells, or leukocytes, are responsible for fighting off infections, allergens and mutated cells. White blood cells come in five varieties: neutrophils, eosinophils, lymphocytes, monocytes and granulocytes. Platelets, or thromboctyes, are responsible for blood clotting. When the body experiences a trauma that results in bleeding, platelets come together to form plugs, or blood clots, to stop the bleeding.
Plasma
Blood is made mostly of plasma, a liquid in which the blood cells are suspended, according to the Merck Manuals Online Medical Library. Blood plasma is 90 percent water, but also contains dissolved salts and minerals, glucose and proteins. Blood plasma has many functions. It prevents blood vessels from collapsing, helps maintain blood pressure and circulation, helps regulate body temperature and aids in fluid control in the body.
Circulation
Blood circulates in two ways: systemic circulation and pulmonary circulation. In the systemic loop, the blood enters the heart from the lungs, where it is pushed out of the aorta, the major artery in the heart. From the heart, the blood circulates throughout the entire body, providing the organs and tissues with oxygen and nutrients and picking up carbon dioxide and waste. In the pulmonary loop, the blood circulates to the lungs from the heart and back. When the blood reaches the lungs, it releases carbon dioxide and picks up oxygen, which it brings back to the heart, according to the University of Colorado.
Types
Blood comes in four types: A, B, AB and O. Blood type is determined by the genes inherited by your parents. Type A blood types carry only the “A” antigen, type B blood types carry only the “B” antigen, type AB blood types carry both antigens and type O blood types carry neither antigen. Those with blood type O are considered universal blood donors because they can donate blood for any blood type.
