The lymphatic system is part of the vascular system and an important part of the immune system, comprising a large network of lymphatic vessels that carry a clear fluid called lymph directionally towards the heart. The lymphatic system was first described in the seventeenth century independently by Olaus Rudbeck and Thomas Bartholin. Unlike the circulatory system, the lymphatic system is not a closed system. The human circulatory system processes an average of 20 litres of blood per day through capillary filtration, which removes plasma while leaving the blood cells. Roughly 17 litres of the filtered plasma is reabsorbed directly into the blood vessels, while the remaining three litres remain in the interstitial fluid. One of the main functions of the lymph system is to provide an accessory return route to the blood for the surplus three litres.
In human anatomy, the thoracic duct is the larger of the two lymph ducts of the lymphatic system. It is also known as the left lymphatic duct, alimentary duct, chyliferous duct, and Van Hoorne's canal. The other duct is the right lymphatic duct. The thoracic duct carries chyle, a liquid containing both lymph and emulsified fats, rather than pure lymph. Thus when it ruptures, the resulting flood of liquid into the pleural cavity is known as chylothorax.
The lymphatic vessels are thin-walled vessels (tubes) structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessels are lined by endothelial cells, and have a thin layer of smooth muscle, and adventitia that bind the lymph vessels to the surrounding tissue. Lymph vessels are devoted to the propulsion of the lymph from the lymph capillaries, which are mainly concerned with absorption of interstitial fluid from the tissues. Lymph capillaries are slightly larger than their counterpart capillaries of the vascular system. Lymph vessels that carry lymph to a lymph node are called afferent lymph vessels, and those that carry it from a lymph node are called efferent lymph vessels, from where the lymph may travel to another lymph node, may be returned to a vein, or may travel to a larger lymph duct. Lymph ducts drain the lymph into one of the subclavian veins and thus return it to general circulation.
The posterior triangle is a region of the neck.
The right lymphatic duct, about 1.25 cm. in length, courses along the medial border of the Scalenus anterior at the root of the neck. The right lymphatic duct forms various combinations with the right subclavian vein and right internal jugular vein. A right lymphatic duct that enters directly into the junction of the internal jugular and subclavian veins is uncommon. The discovery of this structure has been credited to Niels Stensen.
This article describes the anatomy of the head and neck of the human body, including the brain, bones, muscles, blood vessels, nerves, glands, nose, mouth, teeth, tongue, and throat.
Cervical lymph nodes are lymph nodes found in the neck. Of the 800 lymph nodes in the human body, 300 are in the neck. Cervical lymph nodes are subject to a number of different pathological conditions including tumours, infection and inflammation.
The axillary lymph nodes or armpit lymph nodes drain lymph vessels from the lateral quadrants of the breast, the superficial lymph vessels from thin walls of the chest and the abdomen above the level of the navel, and the vessels from the upper limb. They are divided in several groups according to their location in the armpit. These lymph nodes are clinically significant in breast cancer, and metastases from the breast to the axillary lymph nodes are considered in the staging of the disease.
An apical group of six to twelve glands is situated partly posterior to the upper portion of the Pectoralis minor and partly above the upper border of this muscle.
The deep cervical lymph nodes are a group of cervical lymph nodes found near the internal jugular vein.
The jugular trunk is a lymphatic vessel in the neck. It is formed by vessels that emerge from the superior deep cervical lymph nodes and unite to efferents of the inferior deep cervical lymph nodes.
The superior deep cervical lymph nodes lie under the sternocleidomastoid muscle in close relation with the accessory nerve and the internal jugular vein.
The submental lymph nodes are situated between the anterior bellies of the digastric muscle.
Supraclavicular lymph nodes are lymph nodes found superior to the clavicle, palpable in the supraclavicular fossa. The supraclavicular lymph nodes on the left side are called Virchow's nodes.
The deep parotid lymph nodes are lymph nodes found below the parotid gland.
Parotid lymph nodes are lymph nodes found near the parotid gland in the immune system.
A lymph duct is a great lymphatic vessel that empties lymph into one of the subclavian veins. There are two lymph ducts in the body—the right lymphatic duct and the thoracic duct. The right lymphatic duct drains lymph from the right upper limb, right side of thorax and right halves of head and neck. The thoracic duct drains lymph into the circulatory system at the left brachiocephalic vein between the left subclavian and left internal jugular veins.
Lymph sacs are a part of the development of the human lymphatic system, known as lymphangiogenesis. The lymph sacs are precursors of the lymph vessels. These sacs develop through the processes of vasculogenesis and angiogenesis. However, there is evidence of both of these processes in different organisms. In mice, it is thought that the lymphatic components form through an angiogenic process. But, there is evidence from bird embryos that gives rise to the idea that lymphatic vessels arise in the embryos through a vasculogenesis-like process from the lymphangioblastic endothelial precursor cells.
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