The axillary nodes
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The axillary nodes are a group of lymph nodes located in the axillary (or armpit) region of the body. They perform the vital function of filtration and conduction of lymph from the upper limbs, pectoral region, and upper back.
The axillary lymph nodes are a group of twenty to thirty large lymph nodes located in the deep tissues in and around the armpit. These nodes are arranged into five distinct groups: pectoral (anterior), lateral, subscapular (posterior), central (intermediate), and subclavicular (medial). Each group of lymph nodes receives lymph from a specific region of the body or from another group of lymph nodes.
- The pectoral group consists of four or five large lymph nodes located at the superior border of the pectoralis major muscle. These lymph nodes receive lymph from afferent lymphatic vessels in the mammary and pectoral regions of the chest. Efferent lymphatic vessels from this group carry lymph to the central lymph nodes.
- Bordering the lateral edge of the pectoral group is the lateral group. The lateral group consists of four to six lymph nodes clustered around the axillary vein. Lymph from lymph vessels in the upper limb (arm) feeds into the lateral group and is passed on to the central lymph nodes through efferent lymphatic vessels.
- The subscapular group is found in the posterior of the axilla inferior to the scapula, or shoulder blade. Six to seven lymph nodes make up this group, which filters lymph from lymphatic vessels in the back of the neck and upper back. Efferent lymphatic vessels from this group carry lymph to the central lymph nodes.
- The central nodes are a group of three to four lymph nodes embedded in the mass of adipose tissue in the base of the axilla. They further filter lymph that has already been filtered in the pectoral, lateral, and subscapular lymph nodes. Lymph from the central nodes is conducted through lymphatic vessels to the subclavicular nodes just below the clavicle, or collar bone.
- The subclavicular nodes are six to twelve lymph nodes that perform the final round of lymph filtration before passing lymph on to the subclavian trunk.
Lymph is a class of extracellular fluid found in lymphatic vessels and formed from the interstitial fluids of the body. Interstitial fluid is another type of extracellular fluid found surrounding the cells of every tissue in the body. Blood plasma passing through capillaries in the tissues leaks through small gaps in the capillary walls and flows between the cells, forming interstitial fluid. Interstitial fluid plays a vital role in delivering water and nutrients to the tissues while picking up waste materials from the cells. Interstitial fluid also picks up debris from dead cells, viruses, bacteria, and possibly tumor cells. Lymphatic capillaries present in the tissues draw interstitial fluid into their lumens, where it becomes lymph. Lymph is then filtered by lymph nodes and returned to the bloodstream where it once again becomes blood plasma.
Lymph nodes are small organs in the lymphatic system. Their shape bears a resemblance to kidney beans. The exterior of each lymph node consists of a tough capsule made of dense fibrous connective tissue. Reticular tissue containing abundant lymphocytes and macrophages fills the interior of the lymph node. Lymph nodes serve as filters of the lymph that enters from several afferent lymph vessels. Reticular fibers in the reticular tissue work like a net to collect any pathogen or tumor cells in the lymph. The macrophages and T-lymphocytes then attack and kill these pathogens and tumor cells. Once the lymph has been filtered, it passes through efferent lymph vessels, which transport the filtered lymph out of the lymph node en route to the lymphatic ducts.
Lymph passes through several sets of lymph nodes to complete its filtration process, before flowing into larger lymphatic trunks. The subclavian trunks carry lymph from the axillary nodes through the torso to the left and right lymphatic ducts. Both lymphatic ducts return filtered lymph to the subclavian veins, where it becomes part of the blood plasma and returns to the heart for further circulation.