AMA 180 - Anatomy & Physiology/Medical Terminology/Pathology 11 Blood & Lymphatic System Function of the Blood: Maintains a constant environment for living tissues in the body. Transports nutrients, gases (e.g. oxygen and carbon dioxide) and wastes to and from the cells. Transports hormones from glands to distant sites to regulate growth, reproduction and energy production. Contains proteins, white blood cells and antibodies to fight infection, and platelets (thrombocytes) to help with clotting. Composition and Formation of Blood: Cells: formed elements; blood cells originate in the bone marrow (hematopoietic stem cells) and change size and shape to become specialized (differentiated). Plasma: liquid portion of the blood when circulating in the body; carries blood cells through the circulatory system. Composed of water, dissolved proteins, sugar, wastes, salts, hormones, etc. Erythrocytes: red blood cells that contain hemoglobin (protein) that enable them to carry oxygen. Leukocytes: white blood cells come in 5 differentiations (granulocytes, basophils, eosinophils, neutrophils and phagocytes) to help fight off infection through the body’s immune response and the creation of antibodies. Thrombocytes: platelets; clotting cells that are formed in bone marrow from giant cells called megakaryocytes. Lymphatic System Function: Acts as a drainage system to transport, via the bloodstream, proteins and fluid that have leaked into the interstitial fluid surrounding body cells. Absorbs lipids from the small intestine. Creates antibodies. Lymph is clear watery fluid that surrounds cells. Structure of the Lymphatic System: Lymph capillaries: tiny vessels that surround cells and carry lymph from tissues. Lymph vessels: larger vessels that transport lymph to the thoracic cavity. Lymph nodes: collections of stationary lymph tissue that produce lymphocytes and act as filters; contain macrophages, B cells and T cells that destroy foreign substances. Right lymphatic duct: large duct in the upper chest that the lymph vessels empty into; drains the right side of the head and the chest. Thoracic duct: large duct in the upper chest that the lymph vessels empty into; drains the lower body and the left side of the head. Large veins in the neck: lymph is carried here from the ducts where it then enters the bloodstream. Spleen: composed of lymph tissue; destroys old blood cells, filters foreign substances from the blood, activates lymphocytes that produce antibodies and stores blood. Thymus gland: composed of lymph tissue; especially important during childhood and helps with the creation of antibodies and immune cells.