The Immune System The immune system enables the

The Immune System

• The immune system enables the human body to remove many kinds of assaults. • The specialists who diagnose and treat immune system disorders are called immunologists, and the specialty itself is called immunology.

Phagocytes • Phagocytes are often the first immune system cells when injury occurs. They prevent infection by cleaning away pathogens. Two types of phagocytes are microphages and macrophages. Microphages, which constantly circulate in the bloodstream, are more plentiful than macrophages but are shortlived. Macrophages live longer than microphages, and they reside in critical areas, such as the pleural and abdominal cavities, as first-response defenders.

Lymphocytes • When leukocytes (white blood cells) in the bloodstream are needed to fight infection, they leave the blood and enter the lymphatic system; they are then called lymphocytes. They include three different types: NK cells, T cells, and B cells.

NK Cells • NK (natural killer) cells travel throughout the body. Natural killer cells can combat viral infection and malignant cells.

T Cells • They depend on the thymus for activation. B Cells • B cells are derived from bone marrow.

• The Lymphatic System The lymphatic system comprises the vessels through which lymphocytes travel Lymph Like blood plasma, lymph is a fluid that consists mostly of water. It also contains a low concentration of proteins in solution and lymphocytes.

Lymph Vessels • Lymph vessels also called lymph ducts. The largest of the lymph vessels are thoracic duct and the right lymphatic duct.

The Thymus The thymus gland, located behind the sternum, secretes hormones, known collectively as thymosin, which help T cells develop. The thymus is most active in children and gradually and continuously loses some of its function with maturation and further aging.

The Spleen The spleen, which contains phagocytes, removes damaged red blood cells

Lymph Nodes • Lymph nodes are structures of variable size that contain macrophages that filter out diseasecausing antigens.

Tonsils • Any collection of lymph tissue can be called a tonsil. The palatine, pharyngeal, and lingual tonsils.

Term Defintion autoimmunity immune responses against person own healthy cells and tissues antigen substance that induces sensitivity or an immune response in the form of antibodies a molecule generated in specific opposition to an antigen impairment of the immune system antibody immunodeficiency

phagocytosis process of white blood cells clearing away pathogens toxin a poisonous substance