The thoracic duct of the lymphatic system is its main vessel. It can be formed in several ways. Let us consider in detail what the thoracic duct is.
Anatomy
Three membranes are distinguished in the wall of the vessel: endothelial, muscular-fibrous and external. In the first there are 7-9 large semilunar valves. The muscular fibrous membrane has a sphincter at the mouth. The adventitial (outer) part adheres to the pleura, aorta and spine. From the beginning, the abdominal, thoracic, and cervical sections are isolated in the duct. The latter is presented in the form of an arc, and the first two are in the form of a long, well-shaped vessel that accompanies the descending aorta. The abdominal part passes through the aortic fissure in the diaphragm into the chest cavity. Here the thoracic duct runs along the left lateral plane of the lower vertebrae behind the descending aorta. Further, it deviates closer to the esophagus. In the region of the 2nd-3rd thoracic vertebrae, the duct exits from under the esophagus (its left edge). Then, behind the common and subclavian arteries, it rises to the superior aperture. Further, the vessel goes around from above and behind the left part of the pleura. Here, forming an arc, the thoracic duct flows into the venous angle or the branches that form it - the brachiocephalic, subclavian, internal jugular. On thisa site in a vessel the semilunar valve and a sphincter is formed. The thoracic duct is 1-1.5 cm long, in rare cases 3-4 cm.
Formation
Thoracic duct forms:
- Fusion of intestinal, lumbar or both trunks of both sides.
- Formation of milky cistern by branches. In this case, the thoracic duct looks like an ampullar, cone-shaped dilation.
- Merging only the intestinal and lumbar trunks.
The thoracic duct can also form as a reticulate origin in the form of a large looped plexus of celiac, lumbar, mesenteric branches and efferent vessels.
Specific structure
Variability often appears in topography and structure. In particular, it is noted:
- Doubling the thoracic region or the formation of additional (one or more) ducts.
- Different options for interaction with the pleura, aorta, deep neck veins, esophagus.
- Confluence in the venous (jugular) angle, brachiocephalic, subclavian veins with several or one trunk.
- Formation of an ampoule in front of the site of entry into the vessels.
- The tributaries can flow into the jugular angle or the veins that make up it on their own.
Thoracic duct: right lymphatic duct
This element can also be formed in different ways:
- Fusion of the subclavian, jugular, broncho-mediastinal trunks. Whereina short and wide thoracic duct is formed. This situation occurs in 18-20% of cases.
- The right duct may be absent altogether. The trunks that form it open directly into the jugular angle or its constituent vessels. This situation is observed in 80-82% of cases.
- There is a division of a very short, wide right duct before entering the corner into 2-3 or more stems. This form of opening is called network-like.
Trunk
There are three of them:
- Jugular trunk. It is formed by the efferent cervical vessels. They come out of the deep and lateral nodes. This trunk accompanies the internal jugular vein to the angle. In this area, it flows into it or the vessels that form it, or takes part in the formation of the right duct.
- Subclavian trunk. Its occurrence is due to the fusion of the efferent vessels from the axillary nodes. The trunk passes near the subclavian vein, has a sphincter and valves. It opens either into the venous angle and the vessels that form it, or into the right duct.
- Bronchomediastinal trunk. It is formed by efferent vessels from bronchopulmonary, tracheal, mediastinal nodes. There are valves in this trunk. It opens into the right duct, or venous jugular angle, or into the vessels that form it. The latter include the brachiocephalic, subclavian, jugular veins.
The left efferent vessels open in the thoracic duct. From the upper tracheobronchial and mediastinal nodes, they can flow into the venous angle. ATIn the lymphatic trunks, as in the duct, there are three membranes: adventitial, muscular-elastic and endothelial.
Vessels of the lungs and nodes
The capillaries form two networks. One - superficial - is located in the visceral pleura. The second - deep - is formed near the pulmonary lobules and alveoli, around the branches of blood vessels and the bronchial tree. The surface network is represented by a combination of narrow and wide capillaries. It is single layer. The capillaries are presented in the form of a plexus and spread over all surfaces in the visceral pleura. The deep web is three-dimensional. Its main part is the lobular plexus. They send lymph in 2 directions. It enters the plexus of the pulmonary vessels and bronchi, as well as the pleural network. The afferent branches are formed at the level of the segments, pass into the gate and share. They exit the lungs along with the veins and open into the following visceral nodes:
- Bronchopulmonary. They are divided into intraorganic and extraorganic. The former are located at the lobar and segmental bronchi, the latter at the root of the lung.
- Tracheobronchial upper and lower. They lie above and below the tracheal bifurcation.
The efferent vessels drain into the anterior mediastinal and tracheobronchial nodes. Of these, they open into the bronchomediastinal trunk. In rare cases, vessels may drain into the thoracic duct and the jugular venous angle.
