Lymphatic & Immune Systems

Lymphatic & Immune Systems Health Sciences D. Young

Functions of the Lymphatic System • Return cellular waste products and excess fluid from the tissues to the circulatory system. • Absorb fats and fat-soluble vitamins from the digestive system and transport them to the cells. • Serve as an important part of the immune system.

Structures • Lymph fluid • Intercellular fluid/interstitial fluid • Plasma that flows out of the capillaries of the circulatory system into the spaces between the cells. • Carries food, oxygen and hormones to the cells • Lymph fluid • Returns intercellular fluid containing waste products from the cells to the venous circulatory system. Also returns any blood cells that escaped from the capillaries.

Structures Cont’d • Lymph Vessels • Lymph capillaries – thin-walled tubes that carry lymph fluid from the tissues to the larger lymphatic vessels • Right lymphatic duct & the thoracic duct empty lymph into the veins in the upper thoracic region. • Lacteals – specialized lymph capillaries located in the villi of the small intestine. Fats & fat-soluble vitamins are absorbed and carried into the bloodstream.

Structures Cont’d • Lymph Nodes • Small bean-shaped structures located in lymph vessels that provide a site for lymphocyte production. • Filter lymph to remove harmful substances such as bacteria, viruses & malignant cells as lymph flows through the node. • Swollen lymph nodes are often a sign of a disease process.

Structures cont’d • Tonsils • Masses of lymphatic tissue that form a protective rign around the nose and upper throat. • Adenoids – nasopharyngeal Tonsils – located behind the nasopharnx • Palentine tonsils – located in the portion of the throat that is visible through the mouth • Lingual tonsils – located at the base of the tongue.

Structures cont’d • Vermiform Appendix • Lymphatic tissue that hangs from the lower portion of the cecum of the large intestine. • Peyer’s patches – are small areas of lymphatic tissue located on the walls of the large intestine

Structures cont’d • Spleen • Saclike mass of lymphatic tissue located in the left upper quadrant of the abdomen, just below the diaphram & behind the stomach. • Filters microorganisms & other foreign material from the blood • Forms lymphocytes & monocytes which are specialized WBC’s with roles in the immune system. • Is hemolytic – removes and destroys worn-out red blood cells. • Stores extra erythrocytes and maintains the appropriate balance between the red blood cells and plasma in the circulation.

Functions of the Immune System • Protect the body from harmful substances including pathogens, allergens, toxins and malignant cells.

Structures • Not contained within one body system. • Depends on structures from several other body systems.

First Lines of Defense • To keep foreign substances from entering the body • Intact skin – wraps the body in a physical barrier that prevents invading organisms from entering the body • Respiratory system – traps breathed in substances with the nose hairs and the moist mucous membranes that line the respiratory systems. Coughing & sneezing help expel foreign matter from the respiratory system.

Defense Cont’d • Digestive System • Uses acids and enzymes produced by the stomach to destroy invaders that are swallowed or consumed with food. • Lymphatic System • Essential in fighting invaders once they have entered the body.

Immune Response • Antigen-antibody reaction • Antigen • Any substance such as a virus, bacterium, or toxin that the body regards as foreign. Antigens stimulate the immune response. • Antibody • Disease-fighting protein created by the immune system in response to the presence of of that specific antigen. • Immune reaction • Involves binding these foreign antigens to antibodies to form antigen-antibody complexes. This tags the potentially dangerous antigen so that it can be recognized and destroyed.

Specialized Cells • Lymphocytes • Specialized cells formed in bone marrow and undergo further maturation & differentiation in lymphatic tissue throughout the body including the lymph nodes, spleen, thymus, tonsils and Peyer’s patches. • The two major classes of lymphocytes are B cells and T cells.

Specialized Cells cont’d • B Cells • Each B cell is designed to make only one specific antibody against a specific antigen. • Most effective against viruses and bacteria that are circulating in the blood. • Transformed into plasma cells when confronted with the antigen. Enables the body to destroy the antigen in the antigen-antibody response. • Complement – complex series of proteins that circulate in normal serum. Activated on contact with an antigen & aid the antibodies by puncturing the cell membrane of the antigen. • Immunoglobulin (Ig) – synonym for the term antibody. There are five classes of immunoglobulins.

Specialized Cells cont’d • T cells • Also known as T lymphocytes • Small circulating lymphocytes that have traveled to the thymus where they mature as a result of their exposure to thymosin. • Primary function is to coordinate immune defenses and to kill invading organisms on contact.

Specialized cells cont’d • Interferon • Produced by T cells. • A family of proteins released when invaded by a virus. • Causes noninfected cells to form an antiviral protein that slows or stops viral multiplication.

Specialized cells cont’d • Lymphokines • Produced by T cells • Direct the immune response by signaling between the cells of the immune system. • Attract macrophages to the infected site and prepare them for attack

Specialized cells cont’d • Macrophage • Type of phagocyte • Protects the body by ingesting invading cells and by interacting with the other cells of the immune system. • Phagocyte • A WBC with the ability to ingest and destroy substances such as cell debris, dust, pollen, and pathogens. Known as phagocytosis.

Immunity • The state of being resistant or not susceptible to a specific disease. • Natural immunity • Passed from mother to fetus before birth. Also passed from mother to infant in breast milk. • Acquired immunity • Acquired by development of antibodies during an attack of an infectious disease. As an example, after having chickenpox antibodies are present against it. • Artificial immunity • Immunization – immunity acquired through vaccination.

Immune Response Factors • Health • Age • Heredity • Opportunistic Infection

Lymphatic & Immune Systems