Thoracic Duct

Thoracic Duct


THORACIC DUCT 

  • Also c/d as Pacquet duct.
  • The Thoracic Duct is the largest lymphatic vessel(trunk) or great lymph channel, which drains lymph into the bloodstream from the majority of the body. 
  • Appearance of the lymph in thoracic duct is milky white since it includes a product of fat digestion (chyle) from the intestine.
  • Because of presence of numerous valves in its lumen, the duct appears beaded.

 Area of drainage:

  • The thoracic duct drains the lymph from all the parts of the body with the exception of the (a) right side of the head and neck, (b) right side of the chest wall, (c) right lung, (d) right side of the heart, and (e) right surface of the liver.
  • Thoracic duct drains lymph from whole of the body with the exception of the right upper quadrant of the body that is drained by the right lymphatic duct.

Extent:

  • The thoracic duct extends to the upper end of Cisterna chyli on the posterior abdominal wall at the lower border of T12 vertebra to the junction of left internal jugular and left subclavian veins at the root of the neck.

Measurements:

The measurements (normal) of the thoracic duct are as follows:

  • Length: 45 cm (18 inches).
  • Width of lumen: 5 mm (at the ends but narrow in the middle).

FORMATION, COURSE AND TERMINATION

                  

  • The duct begins in the abdomen at the lower border of T12 vertebra, as a continuation of cisterna chyli near the lower border of T12 vertebra and enters the thorax via the aortic opening of the diaphragm (at T12).
  • It then ascends in the posterior mediastinum to the right of midline on the front of vertebral bodies.
  • On reaching the T5 vertebra, it crosses the midline from right to left side and enters the superior mediastinum to run along the left border of the esophagus and reaches the root of the neck.
  • At the level of C7 vertebrae, arches towards left side to open into left brachiocephalic vein at the angle of union of left subclavian & left internal jugular veins.
  • Thoracic duct receives lymph from both halves of the body below the diaphragm & the left half above the diaphragm.

TRIBUTARIES

  • The tributaries of the thoracic duct are as follows:

In the abdomen:

  • Efferent from lower 6 intercostal lymph nodes of both sides.

In the thorax:

  • A pair of the ascending lymph trunks which drains lymph from the upper lumbar lymph nodes (para-aortic lymph nodes).
  • A pair of the descending lymph trunks which drain lymph from the posterior intercostal lymph nodes of upper 6 spaces.
  • Lymph vessels from the posterior mediastinal lymph nodes.

In the neck:

  • Left jugular lymph trunk, draining lymph from the neck.
  • Left subclavian lymph trunk, draining lymph from the left upper limb.
  • Left bronchomediastinal trunk.
Exam Question
 
  • Thoracic duct is also called as Pacquet duct .
  • Length of thoracic duct is  45 cm (18 inches).
  • Thoracic duct does not drains Right upper part of body.
  • Thoracic duct receives lymph from both halves of the body below the diaphragm & the left half above the diaphragm.
  • Thoracic duct enters from abdomen to thorax at T12
  • Thoracic duct opens into Left brachiocephalic vein.
  • Thoracic duct is formed by Continuation of upper end of cisterna chyli.
  • The thoracic duct crosses from the right to the left at the level of T5 vertebrae.
  • Thoracic duct terminates into the left brachiocephalic vein at the junction of Internal jugular vein and subclavian vein
Don’t Forget to Solve all the previous Year Question asked on Thoracic Duct

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