Ch. 21.docx - Ch 21 Lymph and Lymph Vessels Lymphatic system functions Transport and house lymphocytes and other immune cells Return excess fluid in

Ch. 21.docx - Ch 21 Lymph and Lymph Vessels Lymphatic...

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Ch. 21 Lymph and Lymph Vessels Lymphatic system functions Transport and house lymphocytes and other immune cells Return excess fluid in body tissues to blood to maintain blood volume Lymphatic system components Lymph vessels, lymphatic issues and organs Lymph is the fluid transported within lymph vessels Lymph and Lymphatic Capillaries Characteristics of lymph Some fluid leaves blood capillaries and is not reabsorbed by them Such fluid moves into lymphatic capillaries where it is called lymph Components of lymph o Water, dissolved solutes, and small amount of protein o Sometimes cell debris, pathogens, or cancer cells Lymphatic capillaries Small, closed-ended vessels that absorb interstitial fluid Interspersed around most blood capillaries o Absent in avascular tissues, red marrow, spleen, and CNS Slightly larger than blood capillaries; no basement membrane Walls are made of overlapping endothelial cells o Have flaps between cells through which fluid enters but can’t exit o Anchoring filaments hold endothelial cells to nearby structures Lacteals: lymphatic capillaries in GI tract o Absorb lipid-soluble substances from GI tract Movement of lymph into lymphatic capillaries Hydrostatic pressure of interstitial fluid pushes it into capillary o Anchoring filaments linking endothelial cells to surrounding structures prevent vessel collapse o Pressure of lymph inside vessel forces intercellular openings (“flaps”) of capillary wall to close with lymph inside Lymph moves through vessels of larger and larger size o Lymphatic capillaries, lymphatic vessels, lymphatic trunks, and lymphatic ducts o Ultimately, fluid is returned to blood circulation Clinical View: Metastasis Wandering cancerous cells establishing secondary tumors Develop in other locations in the body (metastasis) E.g., breast cancer may metastasize to the lung Cancerous cells break free from primary tumor Transported in the lymph Lymphatic Vessels, Trunks, and Ducts Lymphatic vessels are fed by lymphatic capillaries Located adjacent to arteries and veins Have all three vessel tunics (intima, media, externa) Have valves to prevent pooling and backflow of lymph Lymphatic system lacks a pump; moves lymph using o Skeletal muscles and respiratory pumps (as seen in veins) o Pulsatile movement of blood in nearby arteries o Rhythmic contraction of smooth muscle in larger lymph vessel walls
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Some vessels connect to lymph nodes for lymph filtration Lymphatic trunks are fed by lymphatic vessels Jugular trunks drain lymph from head and neck Subclavian trunks drain upper limbs, breasts, and superficial thoracic wall Bronchomediastinal trunks drain deep thoracic structures Intestinal trunks drain most abdominal structures
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