TOPIC: LYMPHATIC SYSTEM & IMMUNE RESPONSE
Introduction: the major purpose of circulatory system is to bring oxygen and nutrients to the body tissues and absorb wastes and this process occurs in capillaries. Blood plasma containing nutrients move out of capillaries at the arterial end of capillary beds, while tissue fluid containing wastes reabsorbs back in at the venous end.
The lymphatic system is a drainage system that removes excess fluid from body tissues and returns it to the bloodstream Unlike the blood circulatory system, which is a closed-loop, the lymphatic system is a one- direction, open-ended network of vessels.
Explain 3 main functions of the lymphatic system
1. transport proteins & tissue fluids back to the bloodstream 2. participates in the body's immune system (protects the body by removing foreign material such as bacteria from the lymphatic stream and by serving as a site for lymphocyte "policing" of body fluids and for lymphocyte multiplication 3. is the pathway for the absorption of fats from the small intestine into the bloodstream
Explain structures of the lymphatic system 1. Network of lymphatic vessels (lymphatics), 2. Lymphoid tissue, 3. Lymph nodes, Number of other lymphoid organs: tonsils, thymus, spleen . Distribution & function of lymphatic vessels and lymph nodes
Lymphatic capillaries
Made of overlapping endothelial cells The overlapping functions as a one-way valve When fluid accumulates in the tissue, interstitial pressure increases pushing the flaps inward, opening the gap between cells, allowing fluid to flow in. The gaps in lymphatic capillaries are so large, allow bacteria, immune cells such as macrophages, other large particles to enter
Branch through nearly all the tissues of the body -> pick up this leaked fluid and carry it through larger vessels (from collecting lymphatic vessels to lymphatic trunks) until lymph finally returns to blood vascular system via subclavian veins It passes through number of lymph nodes -- serves as filter, cleaning the fluid before it reaches the bloodstream
Right lymphatic duct
jugular, subclavian, & bronchomediastinal trunks Receives lymph from the rest of the body The enlarged terminus of the thoracic duct is the cisterna chyli (receive lymph from digestive organs) Bean shaped, cluster along the lymphatic vessels of the body Found in inguinal, axillary, and cervical regions Lymph nodes contain macrophages and dendritic cells that directly swallow up any pathogens (bacteria or viruses - from infected tissues)
Thoracic duct
Lymph nodes
Lymph nodes also contain Iymphocytes (T cells & B cells) involved in adaptive immune response (this is the process produces activated lymphocytes & antibodies specific to the invading pathogen)
Apart from that, the lymphatic system also contains lymphoid organs (1) Primary lymphoid organs: thymus and bone marrow > the site of lymphocyte production, maturation, and selection (immunocompetent) Selection is the process where lymphocytes learn to distinguish between self & non-self -> so they can recognize & destroy pathogens without attacking body's own cells. (2) Secondary lymphoid organs: the sites where immune responses occur (spleen, lymph nodes, tonsils, and others) SPLEEN Location: upper left portion of