Thoracic duct

Last updated

Thoracic duct
The thoracic and right lymphatic ducts. (Thoracic duct is thin vertical white line at center.)
Gray600 color.png
Modes of origin of thoracic duct. (a) Thoracic duct. (a′)  Cisterna chyli. (b), (c′) Efferent trunks from lateral aortic glands. (d) An efferent vessel which p...[ clarification needed ]
System Lymphatic system
Source cisterna chyli
Drains tojunction of the left subclavian vein and left internal jugular vein
Latin ductus thoracicus
MeSH D013897
TA98 A12.4.01.007
TA2 5137
FMA 5031
Anatomical terminology

In human anatomy, the thoracic duct (also known as the left lymphatic duct, alimentary duct, chyliferous duct, and Van Hoorne's canal) is the larger of the two lymph ducts of the lymphatic system (the other being the right lymphatic duct). [1] The thoracic duct usually begins from the upper aspect of the cisterna chyli, passing out of the abdomen through the aortic hiatus into first the posterior mediastinum and then the superior mediastinum, extending as high up as the root of the neck before descending to drain into the systemic (blood) circulation at the venous angle.


The thoracic duct carries chyle, a liquid containing both lymph and emulsified fats, rather than pure lymph. It also collects most of the lymph in the body other than from the right thorax, arm, head, and neck (which are drained by the right lymphatic duct). [1]

When the duct ruptures, the resulting flood of liquid into the pleural cavity is known as chylothorax.


In adults, the thoracic duct is typically 38–45 cm in length and has an average diameter of about 5 mm. The vessel usually commences at the level of the twelfth thoracic vertebra (T12) and extends to the root of the neck before descending to terminate at the venous angle. [2]


The thoracic duct commences at the upper extremity of the cisterna chyli [3] at the level of the T12 vertebra. [2]

Course and relations


From its origin at the cisterna chyli, the thoracic duct ascends anterior to and to the right of the vertebral column, siuated in between the aorta, and the azygos vein. [3] The thoracic duct traverses the diaphragm at the aortic hiatus [3] to enter the posterior mediastinum. [3]

Posterior mediastinum

It ascends the posterior mediastinum between the descending thoracic aorta (to its left) and the azygos vein (to its right), [4] and is situated posterior to the esophagus at the T7 vertebral level. It crosses the midline to the left side at about the T5 level, continuing to ascend. It then passes posterior to the aorta, and to the left of the oesophagus. [3]

Superior mediastinum

The thoracic ducts ascends into the superior mediastinum, reaching 2-3cm superior to the clavicle, [3] as high up as the C7 vertebral level. [5]

In the superior mediastinum, the thoracic duct is situated posterior to and to the left of the esophagus. It is situated between the visceral and alar fascia. [5] It passes posterior to the left common carotid artery, vagus nerve (CN X), and internal jugular vein. [3] At C7 level, it lies posterolaterally to the carotid sheath. From here, it passes anteroinferiorly to the thyrocervical trunk, and phrenic nerve. [5] It descends until reaching and draining at the venous angle. [3]


The thoracic duct usually [3] drains into the systemic (blood) circulation at the left venous angle where left subclavian and left internal jugular veins unite to form the left brachiocephalic vein. [2] [3]


The characteristic anatomy of the thoracic duct is present in only about half of individuals. [3]


A cisterna chyli is absent in about half of individuals; the cisterna chyli fails to develop when the fusion of lumbar trunk during embryologic development occurs above the vertebral level of T12. In such cases, dilation of the lumbar trunks may be present instead. [3]

Number of ducts

A bifid inferior portion of the thoracic duct (due to a failure of fusion during embryonic development) is not uncommonly observed; a plexus of lymphatic vessels replacing the thoracic duct inferiorly and only coalescing into a single duct in the mediastinum may also occur. Rarely, the thoracic duct may be entirely bilaterally paired. [3]


In over 95% of individuals, the thoracic duct ends by draining either at the venous angle, or into the internal jugular vein, or the subclavian vein, but - in the minority of cases - empties into either the brachiocephalic vein, external jugular vein, suprascapular vein, transverse cervical vein, or vertebral vein. [3]

In a vast majority of cases, the thoracic duct terminates on the left side, but may rarely terminate on the right side of the body, or bilaterally. It usually terminates as a single vessel, but it sometimes ends in bilateral vessels or as several terminal branches. Rarely, the thoracic duct terminates "prematurely" by emptying into the azygous system. [3]


The thoracic duct collects most of the lymph in the body other than from the right thorax, arm, head, and neck. [6] These are drained by the right lymphatic duct. [1]

Diagram showing parts of the body that drain into the right lymphatic duct. Diagram showing the parts of the body the lymphatic and thoracic ducts drain CRUK 323.svg
Diagram showing parts of the body that drain into the right lymphatic duct.

The lymph transport, in the thoracic duct, is mainly caused by the action of breathing, aided by the duct's smooth muscle and by internal valves which prevent the lymph from flowing back down again. There are also two valves at the junction of the duct with the left subclavian vein, to prevent the flow of venous blood into the duct. In adults, the thoracic duct transports up to 4 L of lymph per day. [7]

Clinical significance

The thoracic duct becomes adaptively dilated in the presence of certain pathological conditions (congestive heart failure, portal hypertension, and malignancy). [3]

The first sign of a malignancy, especially an intra-abdominal one, may be an enlarged Virchow's node, a lymph node in the left supraclavicular area, in the vicinity where the thoracic duct empties into the left brachiocephalic vein, right between where the left subclavian vein and left internal jugular join (i.e., the left Pirogoff angle). When the thoracic duct is blocked or damaged a large amount of lymph can quickly accumulate in the pleural cavity, this situation is called chylothorax.

Additional images

See also

Related Research Articles

<span class="mw-page-title-main">Brachiocephalic artery</span>

The brachiocephalic artery is an artery of the mediastinum that supplies blood to the right arm and the head and neck. It was previously known as the innominate artery, meaning unnamed artery.

<span class="mw-page-title-main">Brachiocephalic vein</span> Vein

The left and right brachiocephalic veins are major veins in the upper chest, formed by the union of each corresponding internal jugular vein and subclavian vein. This is at the level of the sternoclavicular joint. The left brachiocephalic vein is more than twice the length of the right brachiocephalic vein.

<span class="mw-page-title-main">Subclavian artery</span> Major arteries of the upper thorax, below the clavicle

In human anatomy, the subclavian arteries are paired major arteries of the upper thorax, below the clavicle. They receive blood from the aortic arch. The left subclavian artery supplies blood to the left arm and the right subclavian artery supplies blood to the right arm, with some branches supplying the head and thorax. On the left side of the body, the subclavian comes directly off the aortic arch, while on the right side it arises from the relatively short brachiocephalic artery when it bifurcates into the subclavian and the right common carotid artery.

<span class="mw-page-title-main">Azygos vein</span> Human blood vessel by the spine

The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for blood to the right atrium when either of the venae cavae is blocked.

<span class="mw-page-title-main">Mediastinum</span> Central part of the thoracic cavity

The mediastinum is the central compartment of the thoracic cavity. Surrounded by loose connective tissue, it is an undelineated region that contains a group of structures within the thorax, namely the heart and its vessels, the esophagus, the trachea, the phrenic and cardiac nerves, the thoracic duct, the thymus and the lymph nodes of the central chest.

<span class="mw-page-title-main">Periaortic lymph nodes</span>

The periaortic lymph nodes are a group of lymph nodes that lie in front of the lumbar vertebrae near the aorta. These lymph nodes receive drainage from the gastrointestinal tract and the abdominal organs.

<span class="mw-page-title-main">Subclavian vein</span> Blood vessel that drains the arm

The subclavian vein is a paired large vein, one on either side of the body, that is responsible for draining blood from the upper extremities, allowing this blood to return to the heart. The left subclavian vein plays a key role in the absorption of lipids, by allowing products that have been carried by lymph in the thoracic duct to enter the bloodstream. The diameter of the subclavian veins is approximately 1–2 cm, depending on the individual.

<span class="mw-page-title-main">Common carotid artery</span> One of the two arteries that supply the head and neck with blood

In anatomy, the left and right common carotid arteries (carotids) are arteries that supply the head and neck with oxygenated blood; they divide in the neck to form the external and internal carotid arteries.

<span class="mw-page-title-main">Superior thoracic aperture</span>

The superior thoracic aperture, also known as the thoracic outlet, or thoracic inlet refers to the opening at the top of the thoracic cavity. It is also clinically referred to as the thoracic outlet, in the case of thoracic outlet syndrome. A lower thoracic opening is the inferior thoracic aperture.

<span class="mw-page-title-main">Cisterna chyli</span>

The cisterna chyli or receptaculum chyli is a dilated sac at the lower end of the thoracic duct in most mammals into which lymph from the intestinal trunk and two lumbar lymphatic trunks flow. It receives fatty chyle from the intestines and thus acts as a conduit for the lipid products of digestion. It is the most common drainage trunk of most of the body's lymphatics. The cisterna chyli is a retroperitoneal structure.

<span class="mw-page-title-main">Thoracic aorta</span>

The thoracic aorta is a part of the aorta located in the thorax. It is a continuation of the aortic arch. It is located within the posterior mediastinal cavity, but frequently bulges into the left pleural cavity. The descending thoracic aorta begins at the lower border of the fourth thoracic vertebra and ends in front of the lower border of the twelfth thoracic vertebra, at the aortic hiatus in the diaphragm where it becomes the abdominal aorta.

<span class="mw-page-title-main">Hemiazygos vein</span>

The hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column.

<span class="mw-page-title-main">Right lymphatic duct</span> Lymphatic Vessel

The right lymphatic duct is an important lymphatic vessel that drains the right upper quadrant of the body. It forms various combinations with the right subclavian vein and right internal jugular vein.

<span class="mw-page-title-main">Jugular lymph trunk</span>

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.

<span class="mw-page-title-main">Outline of human anatomy</span> Overview of and topical guide to human anatomy

The following outline is provided as an overview of and topical guide to human anatomy:

<span class="mw-page-title-main">Lymph duct</span>

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 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.

The venous angle is the junction where the ipsilateral internal jugular vein and subclavian vein unite to form the ipsilateral brachiocephalic vein. The thoracic duct drains at the left venous angle, and the right lymphatic duct drains at the right venous angle. At the venous angle, the carotid sheath and axillary sheath intermingle, forming a continuous neurovascular ensheathment.


  1. 1 2 3 Schuenke, Michael; Schulte, Erik; Schumacher, Udo; Ross, Lawrence M.; Lamperti, Edward D.; Voll, Markus; Wesker, Karl (24 May 2006). Thieme Atlas of Anatomy: Neck and internal organs. Thieme. pp. 136ff. ISBN   978-3-13-142111-1 . Retrieved 1 June 2010.
  2. 1 2 3 Ellis, Harold; Insull, Phillip (1 October 2007). "Clinical Anatomy: Applied anatomy for students and junior doctors". ANZ Journal of Surgery (11th ed.). 77 (10): 911–912. doi:10.1111/j.1445-2197.2007.04191.x. ISSN   1445-2197. S2CID   70800205.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Ilahi, Maira; St Lucia, Kayla; Ilahi, Tahir B. (2022), "Anatomy, Thorax, Thoracic Duct", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   30020599 , retrieved 30 December 2022
  4. Schipper, Paul; Sukumar, Mithran; Mayberry, John C. (1 January 2008), Asensio, JUAN A.; Trunkey, DONALD D. (eds.), "Pertinent Surgical Anatomy of the Thorax and Mediastinum", Current Therapy of Trauma and Surgical Critical Care, Philadelphia: Mosby, pp. 227–251, doi:10.1016/b978-0-323-04418-9.50037-0, ISBN   978-0-323-04418-9 , retrieved 18 November 2020
  5. 1 2 3 Quiñones-Hinojosa, Alfredo (2021). Schmidek and Sweet: Operative Neurosurgical Techniques 2-Volume Set (7th ed.). Philadelphia, PA: Elsavier. p. 2076. ISBN   978-0-323-41519-4. OCLC   1253347770.
  6. Jacob, S. (1 January 2008), Jacob, S. (ed.), "Chapter 3 - Thorax", Human Anatomy, Churchill Livingstone, pp. 51–70, doi:10.1016/b978-0-443-10373-5.50006-3, ISBN   978-0-443-10373-5 , retrieved 18 November 2020
  7. Tewfik, Ted L.; Mosenifar, Zab (7 December 2017). "Thoracic Duct Anatomy". Medscape. WebMD Health Professional Network.