Almost half of the volume of blood consists of blood cells; these include red blood cells (erythrocytes), which carry oxygen to tissues; white blood cells (leukocytes), which fight infection; and platelets (thrombocytes), which are involved in blood clotting. The remainder of the blood volume is a watery, strawcoloured fluid called plasma, which contains dissolved proteins, sugars, fats, salts, and minerals. Nutrients are transported in the blood to the tissues after absorption from the intestinal tract or after release from storage depots such as the liver. Waste products, including urea and bilirubin are carried in the plasma to the kidneys and liver respectively.
Plasma proteins include fibrinogen; which is involved in blood clotting; immunoglobulins (also called antibodies) and complement, which are part of the immune system; and albumin. Hormones are also transported in the blood to their target organs.... blood
Red blood cells (also known as RBCs, red blood corpuscles, or erythrocytes) transport oxygen from the lungs to the tissues (see respiration). Each is packed with haemoglobin, enzymes, minerals, and sugars. Abnormalities can occur in the rate at which RBCs are either produced or destroyed, in their numbers, and in their shape, size, and haemoglobin content, causing forms of
anaemia and polycythaemia (see blood, disorders of).
White blood cells (also called WBCs, white blood corpuscles, or leukocytes) protect the body against infection and fight infection when it occurs. The 3 main types of are granulocytes (also called polymorphonuclear leukocytes), monocytes, and lymphocytes. Granulocytes are further classified as neutrophils, eosinophils, or basophils, and each type of granulocyte has a role in either fighting infection or in inflammatory or allergic reactions. Monocytes and lymphocytes also play an important part in the immune system. Lymphocytes are usually formed in the lymph nodes. One type, a T-lymphocyte, is responsible for the delayed hypersensitivity reactions
White (see allergy) and Red blood blood cell is also involved in cell (neutrophil) protection against cancer. T-lymphocytes manufacture chemicals, known as lymphokines, which affect the function of other cells. In addition, the T-cells moderate the activity of B-lymphocytes, which form the antibodies that can prevent a second attack of certain infectious diseases. Platelets (also known as thrombocytes), are the smallest blood cells and are important in blood clotting.
The numbers, shapes, and appearance of the various types of blood cell are of great value in the diagnosis of disease (see blood count; blood film).... blood cells