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Describe the course and drainage of the thoracic duct. Add a note on chylothorax.

Anatomy · 1st Professional — Pre-Clinical

Definition

The thoracic duct is the largest lymphatic vessel in the body, about 45 cm long, draining lymph from most of the body into the venous system.

Origin and Course

  • The cisterna chyli is formed by the union of the right and left lumbar trunks and the intestinal trunk
  • The duct is beaded in appearance because of its numerous valves

Area of Drainage

Drained by the thoracic ductDrained by the right lymphatic duct
Both lower limbsRight side of the head and neck
Whole abdomen and pelvisRight upper limb
Left half of the thoraxRight half of the thorax
Left upper limb—
Left side of the head and neck—
— that is, the whole body except the right upper quadrant— the right upper quadrant only
  • Three quarters of the body drains through the thoracic duct
  • It carries 1–2 litres of lymph a day, including chyle — the fat absorbed from the intestine, which makes it milky after a meal

Tributaries

  • Descending thoracic lymph trunks from the lower intercostal spaces of both sides
  • Upper intercostal lymph trunks of the left side
  • In the neck — the left jugular, left subclavian and left bronchomediastinal trunks (these may open separately into the veins)

Clinical Importance — Virchow’s Node

Applied Aspects

  • Chylothorax — injury to the duct causes milky lymph to collect in the pleural cavity. Injury above T5 gives a left-sided chylothorax; below T5 a right-sided one, because of where the duct crosses
  • Causes of injury — oesophagectomy, thoracic aneurysm surgery, penetrating trauma, and malignant obstruction
  • Chyluria and chylous ascites occur in filariasis, from lymphatic obstruction — important in India
  • The duct can be ligated safely, because abundant lymphaticovenous communications open up
  • Its variability is considerable — it may be double, or open by several channels, which is why it is easily injured in surgery of the posterior mediastinum and root of the neck

All questions in Thorax

  1. Q1Define the mediastinum and describe its divisions with their contents. Add a note on the structures at the level of the sternal angle. ★
  2. Q2Describe the chambers of the heart, its conducting system and its blood supply. Add a note on the surface marking of the valves. ★
  3. Q3Describe the lungs with their lobes, fissures and root. Explain bronchopulmonary segments and add a note on the pleura. ★
  4. Q4Describe the diaphragm under origin, openings, nerve supply and actions. Add a note on its applied anatomy. ★
  5. Q5Describe the intercostal space with its muscles, vessels and nerves. Add a note on the thoracic cage and applied aspects. ★
  6. SN1Describe the coronary circulation with its branches and peculiarities. ★
  7. SN2Describe the pericardium with its layers and sinuses. Add a note on cardiac tamponade. ★
  8. SN3Describe the course and distribution of the phrenic nerve. Explain the referred pain to the shoulder. ★
  9. SN4Describe the azygos system of veins and its clinical importance. ★
  10. SN5Describe the course and drainage of the thoracic duct. Add a note on chylothorax. ★
  11. SN6Describe the formation, course and relations of the superior vena cava. Add a note on SVC obstruction. ★
  12. SN7Describe the breast with its lymphatic drainage. Add a note on the surface anatomy of the thorax.

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