2. • The thoracic duct is the largest lymphatic vessel.
• Which drains lymph from most of the body into the bloodstream.
• The lymph in the thoracic duct is milky-white in appearance because it
contains a product of fat digestion (chyle) from the intestine.
• The duct appears beaded due to the presence of numerous valves in its
lumen.
THORACIC DUCT
3. • The thoracic duct drains the
lymph from all the parts of the
body except 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.
• (e) right surface of the liver.
Area of drainage
4. • 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:
• Length: 45 cm (18 inches).
• Width of lumen: 5 mm
5. • The thoracic duct begins below in the abdomen as a dilated sac, the cisterna
chyli.
• It ascends through the aortic opening in the diaphragm, on the right side of the
descending aorta.
• It gradually crosses the median plane behind the esophagus and reaches the left
border of the esophagus at the level of the lower border of the body of the 4th
thoracic vertebra (sternal angle).
• It then runs upward along the left edge of the esophagus to enter the root of the
neck.
• In the root of the neck, it bends laterally behind the carotid sheath and in front
of the vertebral vessels.
• It turns downward in front of the left phrenic nerve and crosses the subclavian
artery to enter the beginning of the left brachiocephalic vein.
FORMATION, COURSE, AND TERMINATION
9. • In the abdomen: Efferent from lower six intercostal
lymph nodes of both sides.
• In the thorax:
• 1. A pair of the ascending lymph trunks which drains lymph
from the upper lumbar lymph nodes (para-aortic lymph
nodes).
• 2. A pair of the descending lymph trunks which drain lymph
from the posterior intercostal lymph nodes of upper six
spaces.
• 3. Lymph vessels from the posterior mediastinal lymph
nodes.
• In the neck:
• 1. Left jugular lymph trunk, draining lymph from the neck.
• 2. Left subclavian lymph trunk, draining lymph from the left
upper limb.
• 3. Left bronchomediastinal trunk.
TRIBUTARIES
10. • Injury of thoracic duct: It is thin walled and may be colorless, therefore, it is
sometimes injured during surgical procedures in the posterior mediastinum.
• Laceration of the thoracic duct during lung surgery results in chyle entering into
the pleural cavity producing a clinical condition called chylothorax.
• Obstruction of thoracic duct: Sometimes in filarial infection, the thoracic duct is
obstructed by microfilarial parasites leading to widespread effects, such as
chylothorax, chyloperitoneum, chyluria, and even the accumulation of chyle in
the tunica vaginalis (chylocele).
Clinical Anatomy