Thoracic Duct

Describe the origin, course and termination of thoracic duct.

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Thoracic duct is the largest lymph duct. It has beaded appearance because of the presence of valves. It drains lymph from all the parts of the body except :

• Right half of head and neck
• Right half of thoracic cavity and right lung
• Right upper limb

Origin

Thoracic duct begins at the upper end of cistern chyli ( at lower border of T12 vertebra )

Course 

• Enters posterior mediastinum by passing through the aortic opening of the diaphragm lying between azygous vein on right side and descending aorta on the left side.
• Ascends up in the posterior mediastinum on the right side of the median plane.
• Crosses from right to left side behind the oesophagus and in front of the 5^th thoracic vertebra.
• Ascends in the superior mediastinum along the left of the oesophagus.
• Passes through inlet of thorax and enters root of the neck.
• In the neck it curves laterally in front of vertebral vessels and behind the carotid sheath.

Termination

Drains into the junction of left internal jugular and left subclavian veins.

Name the tributaries and areas drained by thoracic duct.

Tributaries :

• Cysterna chyli located in front of L1 and L2 vertebra. It receives lymph from
  • Intestinal lymph trunk
  • Two lumbar lymph trunks
• Lymphatics from the lower posterior intercostals nodes
• Left bronchomediastinal lymph trunk – drains lymph from lungs  and mediastinum.
• Left jugular lymph trunk – drains lymph from left half of head and neck.
• Left subclavian lymph trunk – drains lymph from left upper limb.

Areas drained by thoracic duct:

• All parts of body below the diaphragm.
• Left half of thoracic region.
• Left upper limb
• Left half of head & neck.

Applied Aspect