Lymphatic trunks and ducts

Lymph from each part of the body, passing through the lymph nodes, is collected in lymphatic ducts (ductus lymphatici) and lymphatic trunks (trunci lymphatici). In the human body, there are six such large lymphatic ducts and trunks. Three of them flow into the left venous angle (the thoracic duct, the left jugular and left subclavian trunks), three - into the right venous angle (the right lymphatic duct, the right jugular and right subclavian trunks).

The largest and main lymphatic vessel is the thoracic duct. Lymph flows through it from the lower limbs, walls and organs of the pelvis, abdominal cavity, left half of the thoracic cavity. From the right upper limb, lymph is directed to the right subclavian trunk, from the right half of the head and neck - to the right jugular trunk, from the organs of the right half of the thoracic cavity - to the right bronchomediastinal trunk (truncus bronchomediastinalis dexter), which flows into the right lymphatic duct or independently into the right venous angle. From the left upper limb, lymph flows through the left subclavian trunk, from the left half of the head and neck - through the left jugular trunk, and from the organs of the left half of the thoracic cavity - to the left bronchomediastinal trunk (truncus bronchomediastinalis sinister), which flows into the thoracic duct.

The thoracic duct (ductus thoracicus) is formed in the abdominal cavity, in the retroperitoneal tissue, at the level of the 12th thoracic - 2nd lumbar vertebrae as a result of the fusion of the right and left lumbar lymphatic trunks (trunci lumbales dexter et sinister). These trunks, in turn, are formed from the fusion of the efferent lymphatic vessels of the right and left lumbar lymph nodes, respectively. In approximately 25% of cases, one to three efferent lymphatic vessels of the mesenteric lymph nodes, which are called intestinal trunks (trunci intestinales), flow into the initial part of the thoracic duct. Efferent lymphatic vessels of the prevertebral, intercostal, and also visceral (preaortic) lymph nodes of the thoracic cavity flow into the thoracic duct. The length of the thoracic duct is 30-40 cm.

The abdominal part (pars abdominalis) of the thoracic duct is its initial part. In 75% of cases, it has an expansion - the thoracic duct cistern (cisterna chyli, milk cistern) of a cone-shaped, ampullar or spindle-shaped form. In 25% of cases, the beginning of the thoracic duct has the form of a reticular plexus formed by the efferent lymphatic vessels of the lumbar, celiac, and mesenteric lymph nodes. The walls of the thoracic duct cistern are usually fused with the right crus of the diaphragm, which, during respiratory movements, compresses the thoracic duct and helps push lymph. From the abdominal cavity, the thoracic (lymphatic) duct passes through the aortic opening of the diaphragm into the thoracic cavity, into the posterior mediastinum, where it is located on the anterior surface of the spinal column, behind the esophagus, between the thoracic part of the aorta and the azygos vein.

The thoracic part (pars thoracica) of the thoracic duct is the longest. It extends from the aortic opening of the diaphragm to the superior aperture of the chest, where the duct passes into its superior cervical part (pars cervicalis). In the lower parts of the thoracic cavity behind the thoracic duct are the initial parts of the right posterior intercostal arteries and the final parts of the veins of the same name, covered by the intrathoracic fascia, and the esophagus is in front. At the level of the VI-VII thoracic vertebrae, the thoracic duct begins to deviate to the left, at the level of the II-III thoracic vertebrae it emerges from under the left edge of the esophagus, ascends behind the left subclavian and common carotid arteries and the vagus nerve. Here, in the superior mediastinum, to the left of the thoracic duct is the left mediastinal pleura, to the right is the esophagus, and behind is the spinal column. Lateral to the common carotid artery and behind the internal jugular vein at the level of the V-VII cervical vertebrae, the cervical part of the thoracic duct curves and forms an arc. The arc of the thoracic duct (arcus ductus thoracici) bends around the dome of the pleura from above and slightly behind, and then the mouth of the duct opens into the left venous angle or into the terminal section of the veins that form it. In approximately 50% of cases, the thoracic duct has a widening before entering the vein. The duct also often bifurcates, and in some cases, in the form of 3-4 trunks, it flows into the venous angle or into the terminal sections of the veins that form it.

At the mouth of the thoracic duct there is a paired valve formed by its internal membrane, preventing the blood from being thrown back from the vein. Along the thoracic duct there are 7-9 valves preventing the backflow of lymph. The walls of the thoracic duct, in addition to the internal membrane (tunica interna) and the external membrane (tunica externa), contain a well-defined middle (muscular) membrane (tunica media), capable of actively pushing lymph along the duct from its beginning to the mouth.

In about a third of cases, there is a duplication of the lower half of the thoracic duct: an additional thoracic duct is located next to its main trunk. Sometimes local splits (doublings) of the thoracic duct are found.

The right lymphatic duct (ductus lymphaticus dexter) is a vessel 10-12 mm long, into which the right subclavian, jugular and bronchomediastinal trunks flow (in 18.8% of cases). Rarely, the right lymphatic duct has one mouth. More often (in 80% of cases), it has 2-3 or more trunks. This duct flows into the angle formed by the confluence of the right internal jugular and subclavian veins, or into the terminal section of the internal jugular or subclavian (very rare) vein. In the absence of the right lymphatic duct (81.2% of cases), the efferent lymphatic vessels of the lymph nodes of the posterior mediastinum and tracheobronchial nodes (right bronchomediastinal trunk), the right jugular and subclavian trunks flow independently into the right venous angle, into the internal jugular or subclavian vein at the place where they merge with each other.

The jugular trunk, right and left (truncus jugularis, dexter et sinister), is formed from the efferent lymphatic vessels of the lateral deep cervical (internal jugular) lymph nodes of the corresponding side. Each jugular trunk is represented by one vessel or several vessels of short length. The right jugular trunk flows into the right venous angle, into the terminal part of the right internal jugular vein or participates in the formation of the right lymphatic duct. The left jugular trunk flows directly into the left venous angle, into the internal jugular vein or, in most cases, into the cervical part of the thoracic duct.

The subclavian trunk, right and left (truncus subclavius, dexter et sinister), is formed from the efferent lymphatic vessels of the axillary lymph nodes, mainly the apical ones, and in the form of one trunk or several small trunks is directed to the corresponding venous angle. The right subclavian trunk opens into the right venous angle or into the right subclavian vein, the right lymphatic duct; the left subclavian trunk - into the left venous angle, the left subclavian vein and in about half the cases into the terminal part of the thoracic duct.

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