The Lymphatic System Luc. 2
*Network of tissues, organs and vessels that help to maintain the body ’s fluid balance & protect it from pathogens · *lymphatic vessels, lymph nodes, spleen, thymus, tonsils, etc · *without it neither the circulatory system nor the immune system would function · *can be thought of as an accessory to the circulatory system · *it helps the circulatory system to do its job · *the two systems are directly connected together · *it consists of fluid derived from plasma =lymph and white blood cells (esp. Lymphocytes and macrophages (monocytes)) *the lymph travels in only one direction - it doesn't circulate
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General functions of lymphatic system: 1.Returns fluid from tissues to blood ~85% of fluids that leak out of blood returns to blood via blood capillaries ~15% returns via lymph capillaries 2. Returns large molecules to blood ~25 -50% of blood proteins leak out of capillaries each day · they cannot get back into capillaries · instead lymphatic capillaries pick them up and return them to the blood.
Venous system Blood capillaries Arterial system Heart Lymph duct Lymph trunk Lymph node Lymphatic system Lymphaüc I collecting vessels, with valves Lymphatic capillay
3. Absorb and transport fats special lymphatic capillaries in villi of small intestine absorb all lipids and fat soluble vitamins from digested food bypasses liver much goes straight to adipose tissues 4 . Hemopoiesis some WBC ’s (lymphocytes, monocytes) are made in lymphatic tissues (not bone marrow) main supply of lymphocytes 5. Body defense/immunity lymphoid tissue is an important component of the immune system (forms a diffuse surveillance defense system in all body tissues and organs · the major role of WBC’s is in body defense · lymphatic system screens body fluids and removes pathogens and damaged cells
Lymph lymph is a clear watery fluid that resembles blood plasma but: has fewer proteins its composition varies depending on organs that it drains . lymphatic vessels (lymphatics): lymphatic capillaries originate in tissues as tiny blind ended Sacs. lie side by side with blood capillaries. single layer of endothelial cells like blood capillaries. but much more permeable to solvents, and large solutes and whole cells. lymphatic vessels - these small lymphatic capillaries merge with others to form larger lymphatic vessels - they resemble veins in structure: three layers – but much thinner. 1-way valves – but many more . also has lymph nodes at intervals along its course. as they converge they become larger and larger.
Loow connective Venule tissue around capillaries Tissue cell (a) Blood capillaries Lymphatic capillary
lymph circulation. * lymph vessels are thin walled, valved structures that carry lymph *lymph is not under pressure and is propelled in a passive fashion *fluid that leaks from the vascular system is returned to general circulation via lymphatic vessels . *Lymph vessels act as a reservoir for plasma and other substances including cells that leaked from the vascular system *the lymphatic system provides a one-way route for movement of interstitial fluid to the cardiovascular system. *Lymph returns the excess fluid filtered from the blood vessel capillaries, as well as the protein that leaks out of the blood vessel capillaries. *Lymph flow is driven mainly by contraction of smooth muscle in the lymphatic vessels but also by the skeletal-muscle pump and the respiratory pump.
Lymph nodes ( also called lymph glands) * oval, vary in size from pinhead to lima bean , most numerous of the lymphatic organs. functions of lymph nodes: 1.Cleanse lymph - as lymph flows through sinuses of node it slows down and microorganisms and foreign matter are removed. 2. Alert immune system to pathogens. 3. Important in hemopoiesis - lymphocytes and monocytes are made here. # lymph moves into nodes by way of several afferent lymphatic vessels , moves through sinus channels lined with phagocytic white blood cells · # exits via 1-3 efferent lymph vessels · # the WBC’s in each node remove ~99% of impurities as lymph passes from node to node virtually all impurities are normally removed ·
lymphatic • Lymphoid Hilum • Medullary
Locations of lymph nodes # lymph nodes are widespread in body but most occur in groups or clusters such as : 1. Submental & submaxillary lymph nodes floor of mouth; drain nose, lips , teeth. 2. Cervical lymph nodes neck drain neck and head 3. Axillary lymph nodes and upper chest drains arm and upper thorax including breasts 4. breasts contains 2 sets of lymphatics: (NOT mammary glands) those that drain the skin over breast excluding the areola and nipple those that originate in and drain deeper portions of breast and skin of areola and nipple 5. abdominal nodes · 6. Inguinal lymph nodes in groin area drain legs and genitals
Major accessory lymphatic organs · spleen – largest · thymus · tonsils · peyers’s patches · appendix
Tonsils (in pharyngeal region) Thymus (in thorax; most active during youth) Spleen (curves around left side of stomach) Peyer's patches (in intestine) Appendix
Spleen * largest of the lymphatic organs. ovoid in shape. *located in the upper left region of abdomen just behind stomach and below diaphragm . *inside is a network of interlacing fibers: red pulp packed with RBC’s white pulp crowded with lymphocytes, monocytes, and neutrophils. performs several functions : 1. Defense helps screen blood and removes pathogens and bacteria 2. Hemopoiesis monocytes and lymphocytes are made here (before birth, RBC’s also made here) 3. Erythrocyte and platelet destruction · it is “erythrocyte graveyard” iron is salvaged from RBC’s
Diaphragrn Adrenal gland Left kidney Splenic artery Pancreas pulp
Thymus gland *is single unpaired organ in mediastinum and neck region * plays vital role in initial set up of body’s immune system source of lymphocytes before birth which circulate to spleen, nodes and vessels soon after birth it secretes a hormone that causes lymphocytes to develop into plasma cells * secretes thymosin and thymopoietin which causes T lymphocytes to become immunocompetent * lacks B cells * atrophies with age: prominent in newborns, stops growth by adolescence, degenerates by old age
Trachea Thymus. Lungs — Diaphragm Liver —