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2 main functions maintaining fluid balance & immunity minor functions collect absorbed fat from the intestines and transport it to the systemic veins lymph watery fluid drained from the tissue spaces that returns excess fluid and protein molecules to the blood via the lymphatic vessels lymphatic fluid found in lymphatic vessels, has elevated protein concentration in thoracic duct because protein-rich lymph from liver/small intestine drains into thoracic duct interstitial fluid fluid that fills the spaces bt the cells of a tissue; along with blood plasma, constitutes extracellular fluid both interstitial fluid & lymph clear isotonic fluids, have similar composition to blood plasma and to each other, have lower protein concentration than blood plasma lymphatic capillaries microscopic blind-end vessels, walls consists of a single layer of flattened endothelial cells; networks branch and anastomose freely lymphatic capillaries merge to form larger lymphatics and eventually form the main lymphatic trunks, R lymphatic ducts, and thoracic duct lymph from upper right quadrant empties into R lymphatic duct and then into R subclavian vein lymph from body empties into thoracic duct, which then drains into the L subclavian vein chyle cistern aka cisterna chyli, what the thoracic duct originates from structure of lymphatic vessels similar to veins except they have thinner walls, many more valves, & contain lymph nodes lymphatic capillary wall formed by single layer of endothelial cells diameter of lymphatic vessels increase from capillary size, walls become thicker, have 3 layers function of lymphatic vessels remove high molecular weight substances and particulate matter from interstitial fluid function of lymphatic vessels lacteals absorbs fats and other nutrients from small intestine, transport through lymphatics to circulation movement of lymph flows through larger lymphatic vessels to reenter blood at junction of the internal jugular and subclavian veins interstitial pressure influences flow of lymph large lymphatic trunks in thorax have small amount of smooth muscle, pulses rythmically to assist in return of lymph lymphokinesis the movement of lymph; can be visualized in a lymphangiogram lymphatic pump moves through system in correct direction because of many valves establish fluid pressure gradient breathing movement & skeletal muscle contractions, as with venous blood lymphkinetic actions activities that result in a central flow of lymph (massage, exercise) structure of lymph nodes oval-shaped structures enclosed by fibrous capsules; biological filter trabeculae aspect of lymph nodes; extend from covering capsule toward center of the node reticuloendothelial cells line the cortical and medullary sinuses; capable of phagocytosis Lymph nodes occur in groups, small structures that performs biological filtration of lymph on its way to the circulatory system important lymph nodes preauricular, submental and submaxillary, superficial cervical, superficial cubital, axillary, iliac, inguinal surveillance lymph node defense filtration lymph node defense; mechanical & biological filtration mechanical filtration physically stopping particles from progressing further in the body biological filtration biologic activity of cells destroys and removes particles by phagocytosis lymphoid tissue site of final maturation of most lymphocytes and monocytes lymph nodes in disease lymph nodes downstream from site of infection become swollen due to the recruitment of lymphocytes lymph nodes role in cancer cancer cells metastasize, break separate from primary tumor and travel through the lymphatics to other parts of the body lymph nodes role in cancer cancer cells may become lodged in lymph nodes forming a metastasis and may ultimately block lymph drainage from that region causing swelling lymphedema swelling of lymph nodes due to infection/cancer lymphedema causes caused by: parasitic worms (elephantiasis), congenital malformation of lymphatics, lymphangitis, tonsillitis, lymphoma, surgical removal of lymph nodes lymphoma cancer of lymph nodes lymphatic drainage of the breast clinically important because cancer cells and infections can spread along lymphatic pathways to lymph nodes and other organs of the body 2 sets of lymphatic tissue in breast 1.drain the skin over breast with exception of areola/nipple 2.drain the underlying substance of breast, as well as skin of areola/nipple; connected to fascia of pectoralis major muscles cutaneous lymphatic plexus collection of lymphatic tissue that drains over breast with exception of areola/nipple subareolar plexus aka Plexus of Sappey; communication between 2 sets of tissue of breast occurs here plexus intricate network or web-like formation 85% of lymph tissue of breast enters the lymph nodes of axillary region; the remainder enters along lateral edges of the sternum tonsils form a discontinuous ring under the mucous membranes in themouth and back of the throat aka pharyngeal lymphoid ring palatine tonsils located on each side of throat pharyngeal tonsils located near the posterior opening of nasal cavity lingual tonsils located near base of tongue tubal tonsils located near the openings of the auditory (eustachian tubes) tonsils protect against bacteria that may invade tissues around the openings bt nasal and oral cavities; bacteria trapped in tonsillar crypts and put in close contact with immune system cells thymus primary central organ of lymphatic system; single, unpaired organ located in mediastinum extending upward to lower edge of thyroid and inferiorly as far as 4th costal cartilage thymus color in childhood pinkish gray thymus color in adulthood yellowish, as lymphoid tissue is replaced with fat; also shrinks with age thymus structure pyramid shaped lobes, subdivided into smaller lobules thymus lobule composed of dense cellular cortex and inner, less dense medulla thymic corpuscles identifies medullary tissue spleen location L hypochondrium, directly beneath diaphragm, above L kidney and descending colon and behind fundus of stomach spleen structure ovoid shape, surrounded by fibrous capsule with inward extensions that divide organ into compartments white pulp part of spleen; dense masses of developing lymphocytes red pulp part of spleen; near outer regions, composed of network of reticular fibers submerged in blood that comes from nearby arterioles; composed of cords of WBCs and related cells surrounded by sinusoids spleen function defense; macrophages lining sinusoids of spleen remove microorganisms from blood and phagocytose them spleen function hematopoiesis; monocytes and lymphocytes complete their development spleen function RBC/platelet destruction;macrophages remove worn out RBCs and imperfect platelets and phagocytose them. Salvage iron/globin from RBCs spleen function blood reservoir; pulp of spleen and its sinuses store blood Unique spleen none of functions unique to spleen, therefore it can be removed without dire consequences Lymphatic system overview drains away excess H2O from large areas, lymph conducted through lymphatic vessels to nodes where contaminants are removed, benefits whole body by maintaining fluid balance and freedom from disease interstitial fluid complex, organized fluid that fills the spaces bt the cells and is part of the ECM; resembles blood plasma in composition with a lower % of protein interstitial fluid, blood plasma _______ ________ and _____ _______ constitutes the extracellular fluid mechanical filtration physically stopping particles from progressing further in the body biological filtration biological activity of cells destroys and removes particles thymus functions plays role in immunity, source of lymphocytes before birth, shortly after birth it secretes thymosin/other regulators which enables lymphocytes to develop into T cells