Thoracic Duct and Lymphatics

Thoracic Duct and Lymphatics

Thoracic Duct and Lymphatics

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Thoracic Duct: Overview - Lymph's Main Highway

  • Largest lymphatic vessel; primary conduit for lymph return to venous system.
  • Drains lymph from ~75% of the body:
    • Both lower limbs, pelvis, abdomen (most parts).
    • Left side of thorax, left upper limb, left head & neck.
  • Origin: Cisterna chyli (dilated sac, anterior to L1-L2 vertebrae).
  • Length: Approx. 38-45 cm; Diameter: 2-5 mm.
  • Terminates: Left venous angle (junction of left internal jugular & left subclavian veins).
  • Contains numerous valves to prevent lymph backflow. Thoracic duct and major lymphatics

⭐ The thoracic duct is responsible for transporting chyle, a lipid-rich lymph, from the intestines to the bloodstream. This gives the lymph a milky appearance after a fatty meal.

Thoracic Duct: Course & Relations - The Upward Journey

  • Origin: Cisterna chyli (anterior to L1-L2 vertebrae).
  • Thoracic Entry (T12): Via aortic hiatus; right of aorta, posterior to esophagus initially.
  • Posterior Mediastinum Ascent (T12-T5):
    • Between descending aorta (left) & azygos vein (right).
    • Posterior to esophagus.
    • 📌 Mnemonic: "A DUCK between two GOOSEs" (Aorta, Duct, AzyGOS vein).
  • Crossing (T5): Inclines left, posterior to esophagus, reaches left side of esophagus.
  • Superior Mediastinum Ascent (T5-C7):
    • Ascends on left of esophagus.
    • Medial to left pleura/lung.
  • Cervical Arch (C7): Arches laterally over apex of left lung; anterior to vertebral vessels & sympathetic trunk.
  • Termination: Left venous angle (junction of L. internal jugular & L. subclavian veins).

Thoracic duct and lymphatics diagram

⭐ The thoracic duct crosses from right to left at the level of the T5 vertebra, posterior to the esophagus.

Thoracic Duct: Tributaries & Drainage - The Great Collector

The body's main lymph collector, draining ~75% of total lymph.

  • Key Tributaries:
    • Cisterna chyli (receives lumbar & intestinal trunks)
    • Intercostal trunks (descending & left upper)
    • Left jugular, subclavian, & bronchomediastinal trunks (terminate into duct)
  • Drainage Areas:
    • Both lower limbs, pelvis, abdomen
    • Left thorax, left upper limb
    • Left side of head & neck Thoracic duct and drainage areas

⭐ Drains all lymph except from the right upper quadrant (served by right lymphatic duct).

Thoracic Lymphatics: Nodes & Vessels - Chest's Drainage Network

Thoracic duct and lymphatic drainage

  • Principal Node Groups:
    • Parietal: Parasternal, intercostal, phrenic (diaphragmatic).
    • Visceral: Tracheobronchial (hilar, carinal), bronchopulmonary, paratracheal, posterior mediastinal.
  • Major Collecting Trunks:
    • Thoracic Duct: Drains ~75% of body; empties into left venous angle (junction of left internal jugular & subclavian veins).
    • Right Lymphatic Duct: Drains ~25% (right head, neck, arm, right thorax); empties into right venous angle.

⭐ Virchow's node (left supraclavicular) enlargement often signals gastric cancer metastasis (Troisier's sign).

Thoracic Duct: Clinical Significance - When Flow is Disrupted

  • Chylothorax: Most common; chyle in pleural space.
    • Causes: Trauma (surgical, accidental), malignancy (esp. lymphoma), congenital, infections.
    • Impact: Malnutrition (↓protein, ↓fat, ↓lymphocytes), immunodeficiency, respiratory distress.
  • Other manifestations: Chylous ascites, chylopericardium.
  • Diagnosis: Fluid: milky, triglycerides > 110 mg/dL, chylomicrons present.
  • Management: Conservative (low-fat diet, MCT oil), octreotide, surgical (ligation, pleurodesis).

    ⭐ Iatrogenic injury during thoracic or neck surgery is the most common cause of chylothorax.

High‑Yield Points - ⚡ Biggest Takeaways

  • Thoracic duct: largest lymphatic channel, drains lymph from ~75% of the body.
  • Origin: cisterna chyli (L1-L2); enters thorax via aortic hiatus (T12).
  • Ascends between descending aorta (left) & azygos vein (right), anterior to vertebrae.
  • Crosses to the left at T5 vertebra (sternal angle).
  • Empties into left venous angle (junction of L. internal jugular & L. subclavian veins).
  • Chylothorax: chyle in pleural space, indicates thoracic duct injury.

Practice Questions: Thoracic Duct and Lymphatics

Test your understanding with these related questions

Anterior Mediastinal nodes are included in which level of lymph nodes?

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Flashcards: Thoracic Duct and Lymphatics

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The thoracic duct lies in the _____ and posterior inferior mediastinum.

TAP TO REVEAL ANSWER

The thoracic duct lies in the _____ and posterior inferior mediastinum.

superior

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