Thoracic ducts

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1. THORACIC DUCT By Dr. Vibhash k. Vaidya

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

6. Fig: Formation, Course, And Termination of Thoracic duct

7. Relations

8. 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

9. 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