Chapter 7 - Peripheral Blood
Blood is a specialized connective tissue composed of cells (red blood cells, white blood cells, and platelets) circulating in a fluid called plasma. It provides a mechanism by which gases, nutrients, wastes, and cells can be transported throughout the body.
RED BLOOD CELL
Red blood cell (erythrocytes) are the most abundant type of blood cell (98% of all cells). Red blood cells transport oxygen to cells and remove carbon dioxide from the same cells.
Sickle Cell Anemia
Sickle cell anemia is an inherited disorder that affects the shape of red blood cells.
Platelets (thrombocytes) are small cell fragments that plug damage blood vessel walls and are involved in the formation of blood clots.
WHITE BLOOD CELL
White blood cells (leukocytes) perform their functions in tissues and use the circulatory system to reach their destination.
Granulocytes have a multilobed nucleus and contain specific granules in their cytoplasm. They are divided into three groups (neutrophils, eosinophils, and basophils) according to the staining properties of their specific granules.
Neutrophils (or polymorphonuclear leukocytes) are the most abundant white blood cell (60 to 70%). Phagocytic cells that engulf and kill microbes (bacteria, fungi, and protozoa).
Eosinophils are a small proportion of white blood cells (2 to 4%). They are involved in many inflammatory processes, including parasitic infections, allergic diseases, and asthma.
Basophils are the least common white blood cell (<1%). They are secretory cells that increase inflammation.
Agranulocytes are white blood cells (lymphocytes and monocytes) without specific granules in their cytoplasm.
Lymphocytes are a large component of white blood cells (20 to 25%). They recirculate through tissues and back to the circulation via blood and lymphatic vessels.
Monocytes a small proportion of white blood cells (3 to 8%). They migrate into tissues and differentiate into the various macrophages of the mononuclear phagocytotic system.
Plasma cells usually differentiate from B-lymphocytes in tissues and produce large amounts of antibodies. This is a rare example of one found in blood.
The clotting of blood is an important process that helps the body repair after tissue damage. Platelets travel to the injured are to form a clot. They contribute to stop bleeding via adhesion, activation, and aggregation, which are triggered upon tissue injury. These actions also stimulate coagulation factors and other mediators to stop bleeding.