CELL 220 lecture 18 - lymphatic and immune system

components of lymphatic system

lymphatic vessels, nodules, organs, cells

functions of lymphatic system

return leaked plasma to the bloodstream, screen lymph for foreign substances, house lymphocytes that generate immune response, transport dietary lipids

flow of lymph

lymphatic capillaries → series of lymphatic vessels and lymph nodes → lymphatic trunks → lymphatic ducts → venous circulatioin

lymphatic capillaries 

closed-ended tubes, overlapping endothelial cells from one-way flaps, occur most everywhere blood capillaries occur (absent from red bone marrow, CNS, and avascular tissues), lacteals (small intestine - GI lymph is called chyle)

lymph nodes

afferent and efferent vessels, cortex and medulla, macrophages, dendritic cells, and lymphocytes

functions of lymph nodes

screen lymph for foreign antigens, initiate immune response

locations of lymph nodes

axillary, inguinal, cervical, scattered

lymphatic vessels

recieve lymph from lymphatic capillaries, valves prevent backflow in low pressure system, resemble veins with three tunics, afferent and efferent

lymphatic ducts

final destination - return lymph to cardiovascular system at the junction of the internal jugular and subclavian veins

primary lymphatic organs

bone marrow and thymus

secondary lymph organs

lymph nodes and spleen

spleen

largest lymphatic organ, white pulp (lymphocytes and macrophages, monitors blood for foreign antigens, initiates immune resonse), red pulp (functions as a blood reservoir, hemolysis, remove debris from blood

lymphatic nodules

oval clusters of lymphatic tissue (not surrounded by a connective tissue capsule), contain macrophages, dendritic cells, and lymphocytes

functions of lymphatic nodules

screen for and attack foreign antigens

locations of lymphatic nodules

tonsils, mucosa-associated lymphatic tissue (MALT)

macrophages and dendritic cells

phagocytosis of foreign substances, antigen presentation to lymphocytes to initiate immune response

lymphocytes

most abundant cell type in lymphatic organs and nodules, migrate through the lymphatic system searching for foreign antigens, mount the immune response when activated

t lymphocytes

cytotoxic t cells (CD8+), memory t cells, helper t cells (CD4+) and regulatory cells

b lymphocytes

once activated, they divide and become plasma cells (produce antibodies which bind to antigens, tagging them for destruction) and memory b cells (patrol after an attack, easily deactivated if infected again)

natural killer cells (NK)

respond to multiple antigens, kill a wide variety of infected cells and some cancerous cells