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