The major components of the blood are plasma, red blood cells, white blood cells and platelets. Plasma is a yellowish liquid that contains the other components of the blood as well as many different substances. These include proteins, such as albumin, globulin and fibrinogen.
Blood plasma also contains minerals and sugar. Albumin keeps the plasma inside the blood vessels. When the levels of albumin drop, plasma leaks into the tissues. This leads to edema. Fibrinogen helps in forming blood clots, and globulin has antibodies to fight infection.
Red blood cells, or erythrocytes, contain hemoglobin, which carry oxygen to the cells and carry carbon dioxide from the cells. Red blood cells are created in the bone marrow and are different from regular cells because they lack nuclei.
White blood cells support the immune system by fighting disease and helping to clear pathogens from the system. There are five types of white cells: lymphocytes, neutrophils, eosinophils, basophils and monocytes.
Platelets are tiny blobs of cytoplasm that help repair small wounds and keep blood from leaking out. When a person suffers a cut, platelets accumulate at the wound and help seal the blood vessels there. The platelets also have chemicals that begin the clotting process.