Immune System
Immune system protects the body against invading pathogens including bacteria, viruses, fungi, &
protists. Immune system includes the lymphatic system (lymph, lymph capillaries, lymph vessel, &
lymph nodes) as well as the red bone marrow & numerous leukocytes, or white blood cells. Tissue
fluid enters the lymph capillaries, which combine to form lymph vessels.
Skeletal muscle contractions move the lymph one way through the lymphatic system to
lymphatic ducts, which dump back into the venous blood supply into the lymph nodes,
which are situated along the lymph vessels, & filter the lymph of pathogens & other matter.
Lymph nodes are concentrated in the neck, armpits, & groin areas. Outside the lymphatic
vessel system lies the lymphatic tissue including the tonsils, adenoids, thymus, spleen, &
Peyer’s patches.
Tonsils – located in the pharynx, protect against pathogens entering the body
through the mouth & throat.
Thymus – serves as a maturation chamber for the immature T cells that are formed
in the bone marrow.
Spleen – cleans the blood of dead cells & pathogens.
Peyer’s patches – located in the small intestines, protect the digestive system from
pathogens.
Body’s general immune defenses include:
Skin – an intact epidermis & dermis form a formidable barrier against bacteria.
Ciliated mucous membranes – cilia sweep pathogens out of the respiratory tract.
Glandular secretions – secretions from exocrine glands destroy bacteria.
Gastric secretions – gastric acid destroys pathogens.
Normal bacterial populations – compete with pathogens in the gut & vagina.
