THE ANATOMY OF THE LYMPHATIC SYSTEM & LYMPHATIC DRAINAGE One f the primary functins f the lymphatic system is t cllect and filter tissue fluid, and return it t the circulatin. During this prcess the lymphatic system plays an imprtant rle in bdy defense it detects and traps freign particles and prevents them frm entering the circulatin. In grss anatmy we will fcus n tw cmpnents f the lymphatic system: lymphatic vessels and lymph ndes. Lymph & Lymphatic Vessels Lymph fluid cnsists f excess extracellular fluid and plasma prteins leaked frm capillaries in cnnective tissues. In cases f infectin lymph fluid als cntains pathgens and dendritic cells carrying pathgens frm infected tissues. Lymph draining the small intestine (chyle) als includes emulsified fats. Lymph frm cnnective tissues is cllected and circulated in lymphatic vessels fr eventual return t the bld thrugh the venus system. During its circulatin lymph passes thrugh a series f lymph ndes where it is screened fr freign antigens and pathgens. Lymphatic vessels transprt lymph and chyle. With a few exceptins (e.g., bne, cartilage, the eye) these vessels ccur almst everywhere bld vessels are fund. Lymphatic vessels begin as blind capillaries in the extracellular spaces. These capillaries unite t frm larger lymphatic vessels and eventually even larger lymphatic trunks. Mst lymphatic vessels have valves that allw lymph t flw in nly ne directin. All f the lymph transmitted thrugh lymph vessels is returned t the circulatin at the junctin f the internal jugular vein with the subclavian vein in the rt f the neck (junctin f neck with shulders). These veins are bilateral (they ccur n bth sides f the bdy) and lymph is returned t the circulatin n bth sides. Majr lymphatic vessels Jugular trunks (right and left): lcated in the rt f the neck; each jugular trunk drains lymph frm ne full side f the head and neck (sme midline structures drain their lymph t bth sides). Subclavian trunks (right and left): lcated in the rt f the neck and shulder; each subclavian trunk drains lymph riginating frm the fllwing surces: Upper extremity Superficial fascia and skin f the upper back Superficial fascia and skin f the anterir thracic wall (including the breast) and anterir abdminal wall abve the level f the umbilicus Lymphatic Drainage Page 1
Brnchmediastinal trunks (right and left): lcated deep in the thrax; each brnchmediastinal trunk drains lymph riginating frm the lung, anterir thracic viscera and the musculature f the anterlateral bdy wall abve the level f the umbilicus. Lumbar trunks (right and left): lcated deep in the abdminal cavity; each lumbar trunk drains lymph frm the fllwing surces: Lwer extremity Abdminal wall musculature belw the umbilicus Retrperitneal rgans (e.g., kidney, adrenal gland, ureter) f the abdminal cavity Pelvic rgans External genitalia Intestinal trunks (numerus unpaired): lcated deep in the abdminal cavity; these trunks drain lymph (& chyle) frm the gastrintestinal tract and its accessry rgans. Chyle cistern & thracic duct The chyle cistern is a large cistern f lymph fund in the abdminal cavity, immediately inferir t the thracic diaphragm. It is frmed by the unin f the lumbar and intestinal trunks, and therefre cllects lymph frm all tissues and rgans lcated inferir t the thracic diaphragm. (It als cllects sme lymph frm the deep tissues f the inferir thracic bdy wall.) The thracic duct is a large, unpaired lymphatic vessel that emerges frm the superir aspect f the chyle cistern. The thracic duct ascends deep in the thrax, adjacent t the esphagus, t reach the rt f the neck n the left side. Lymphatic vessels in the rt f the neck As nted abve, all lymph drained frm the bdy s tissues is returned t the venus system in the rt f the neck. On bth the right and left sides f the bdy lymphatic vessels jin the internal jugular vein r subclavian vein where these large vessels unite t frm the brachicephalic vein (the venus angle). MDA7, F6.42B Lymphatic Drainage Page 2
On the right, the right jugular, right subclavian and right brnchmediastinal trunks drain t the right venus angle. On the left, the left jugular, left subclavian, left brnmediastinal trunks, and the thracic duct drain t the left venus angle. By virtue f this pattern f drainage, lymph frm the bdy s right upper quadrant (right side f head & neck, right side f thrax and back, right lung and right upper extremity) flws t the right venus angle; lymph frm the remainder f the bdy, including all abdminal and pelvic viscera, and bth lwer extremities drains t the left venus angle. Nte that the left jugular, subclavian and brnchmediastinal trunks ften empty directly int the thracic duct, rather than the venus angle prper. Similarly, the jugular, subclavian and brnchmediastinal trunks n the right may ccasinally jin t frm a shrt right lymphatic duct at the right venus angle. Gray s Atlas2, p12 Lymph Ndes Lymph ndes are vid r kidney-shaped ndules that vary in length frm a few millimeters t as much as 2 cm. Lymph ndes serve as filters fr the lymph. Any freign particles in the lymph, whether bacterial r inert material, are trapped in the ndes as the lymph passes thrugh the meshwrk f reticular fibers. Clinicians are extremely cnscius f the imprtance f lymph ndes. Lymphatic vessels frequently serve as pathways fr the spread f infectins and cancer and lymph ndes lcated n these paths tend t catch and hld fr a time such bacteria r cancer cells that may reach them. Hard, swllen lymph ndes can therefre be a sign f infectin r an indicatin f metastasis. Fr this reasn it is especially imprtant t learn 1) the lcatins f the reginal lymph ndes that drain the different areas f the bdy, and 2) the rutes f lymphatic drainage frm particular rgans. The terms lymphangitis and lymphadenitis refer t the secndary inflammatin f lymphatic vessels and lymph ndes, respectively ( angi = vessel; aden = gland). Lymphedema is an accumulatin f interstitial fluid that ccurs when lymph is nt drained frm an area f the bdy. Fr instance, if cancerus lymph ndes are remved frm the axilla as part f breast cancer treatment, lymphedema f the upper limb may result. Palpable Lymph Ndes In general, large lymph ndes are lcated deep within the bdy cavities r in ther, nn-palpable lcatins. Superficially-lcated lymph ndes tend t be small and even the larger f these are palpable nly when enlarged due t infectin r metastasis. The mre imprtant f these ptentially palpable lymph ndes are as fllws: Lymphatic Drainage Page 3
Axillary lymph ndes: lcated in the axilla (anatmical term fr armpit ), these lymph ndes receive three streams f lymph, ne frm the upper extremity, ne frm the superficial fascia f the adjacent thracic and upper abdminal wall and breast, and ne frm the superficial fascia f the upper back. The three currents meet and merge deep within the axilla. Lymph frm the axillary ndes drains t a subclavian trunk. Inguinal lymph ndes: lcated immediately inferir t the inguinal ligament in the grin area, inguinal ndes are divided int superficial and deep grups. They receive lymph primarily frm the lwer extremity and superficial fascia f the trunk inferir t the umbilicus including the external genitalia. After passing thrugh inguinal ndes, lymph drains t the lumbar lymphatic trunks and chyle cistern. Sbtta Atlas V.1, Fig 1.37 Deep cervical chain: lcated alng the curse f the internal jugular vein in the neck, this cllectin f 15-30 lymph ndes receive lymph frm the head & neck. One f the ndes within this grup, the tnsillar nde (juguldigastric nde) receives lymph frm the palatine tnsils in the back f the thrat. Lymph frm the deep cervical chain drains t the jugular trunk. MDA7, F7.26B Sme f the inferir ndes in the deep cervical chain receive lymph frm the upper limb and anterir thracic wall as well as the head & neck. On the left these supraclavicular ndes als take part in filtering the lymph passing thrugh the thracic duct. The supraclavicular ndes are smetimes clinically imprtant as their enlargement can be the first sign f cancer f rgans and tissues lcated deep within the thrax, abdmen r pelvis. Lymphatic Drainage Page 4
Guide t figure surce abbreviatins: MDA7: Mre, Dalley & Agur, Clinically Oriented Anatmy, 7e, 2014: Wlters Klewer Lippinctt, Williams & Wilkins Gray s Anatmy3: Drake, Gray s Anatmy fr Students, 3e, 2015: Churchill Livingstne Elsevier Gray s Atlas2: Drake, Gray s Atlas f Anatmy, 2e, 2015: Churchill Livingstne Elsevier Sbtta s Atlas: Paulsen & Waschke, Sbtta Atlas f Human Anatmy, Vl. 1, Fifteenth Editin, 2016: Elsevier Lymphatic Drainage Page 5