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Structure

Thoracic duct

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The thoracic duct is the largest lymphatic vessel, about 40 cm long. It collects lymph from the whole body below the diaphragm and from the left side of the thorax, head, neck and upper limb, and empties into the left venous angle.

Terminologia Anatomica (Latin): Ductus thoracicus · Open in the 3D atlas

Location

It begins at the cisterna chyli (L1 to L2) to the right of the aorta, passes through the aortic hiatus at T12, ascends in the posterior mediastinum between the aorta and the azygos vein, crosses to the left around T4 to T5, and arches over the cervical pleura at the level of C7 behind the left carotid sheath.

Structure

A thin-walled vessel with numerous valves, formed by the union of the intestinal and lumbar lymphatic trunks at the cisterna chyli. It receives bronchomediastinal, left subclavian and left jugular trunks near its termination. The right lymphatic duct drains the right upper quadrant of the body separately.

Blood supply

There is no single named artery; the wall is supplied by small branches of neighbouring vessels such as the posterior intercostal and inferior thyroid arteries.

Innervation

Sympathetic fibres from the thoracic sympathetic trunk supply the smooth muscle of the wall, which contributes to propulsion of lymph together with valves, respiratory movements and adjacent arterial pulsation.

Function

It returns interstitial fluid and protein to the venous system and transports dietary fat absorbed as chylomicrons from the intestine, giving intestinal lymph (chyle) its milky appearance after a fatty meal.

Clinical correlations

Injury during oesophageal, thoracic or neck surgery, or obstruction by lymphoma or other tumours, can cause chylothorax or chylous ascites, with triglyceride-rich milky fluid. Metastases may reach the left supraclavicular (Virchow) node. Because the duct is thin and variable, anatomy differs between individuals.

Common exam points

  • Begins at the cisterna chyli (L1 to L2) and passes through the aortic hiatus at T12.
  • Lies in the posterior mediastinum between the aorta and the azygos vein.
  • Drains into the left venous angle (junction of left internal jugular and subclavian veins).
  • Drains most of the body; the right lymphatic duct drains only the right upper quadrant.
  • Chylothorax is a recognised complication of oesophagectomy and thoracic surgery.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)

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