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The thoracic duct is the largest lymphatic vessel in the body, allowing return of lymph from most of the body (all but the right superior quadrant) into the venous system.
The duct originates from the cisterna chyli in the abdomen, and enters the mediastinum through the aortic hiatus.
It ascends to lie directly anterior to the T6-T12 vertebrae, before deviating left as it ascends into the superior mediastinum.
While located in the posterior mediastinum, the thoracic duct receives lymphatic drainage from the intercostal spaces and neighboring anatomical structures through a number of branches. Thoracic Duct MBBSPPT.COM 2<br>
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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.
It is pale, thin walled vessel about the size of a drinking straw.
It does have a product of fat digestion (chyle) from the intestine.
Due to the presence of numerous valves in its lumen, the duct appears beaded. Thoracic Duct MBBSPPT.COM 4<br>
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Thoracic Duct MBBSPPT.COM 5<br>
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The thoracic duct drains the lymph from all the parts of the body with the exception of:
Right side of the head and neck,
Right side of the chest wall,
Right lung,
Right side of the heart, and
Right surface of the liver.
The right upper quadrant of the body that is drained by the right lymphatic duct. Area of drainage MBBSPPT.COM 6<br>
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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. Extent MBBSPPT.COM 8<br>
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The measurements (normal) of the thoracic duct are as follows:
Length: 45 cm (18 inches).
About the size of a drinking straw.
Width of lumen: 5 mm (at the ends but narrow in the middle). Measurements MBBSPPT.COM 10<br>
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FORMATION, COURSE AND TERMINATION MBBSPPT.COM 12<br>
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The duct begins in the abdomen at the lower border of T12 vertebra, as a continuation of cisterna chyli.
It enters the thorax via the aortic opening of the diaphragm separating aorta from the azygos vein.
It then ascends in the posterior mediastinum to the right of midline on the front of lower thoracic vertebra between the descending aorta (on its left) and azygos vein ( on its left).
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. COURSE in the thorax & abdomen MBBSPPT.COM 13<br>
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At the root of neck it arches laterally at the level of C7 vertebra in front of vertebral vessels and left cervical sympathetic trunk and behind the carotid sheath.
The summit of arch is located 3-4 cm above the clavicle.
Finally, the duct descends in front of the first part of left subclavian artery and finally ends by opening into the junction of left subclavian and left internal jugular veins.
The thoracic duct begins in abdomen, courses via thorax and ends in the neck. COURSE in the neck MBBSPPT.COM 14<br>
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In The Posterior Mediastinum,
Anterior:
Diaphragm.
Descending aorta (lower part).
Esophagus (upper part).
Posterior:
Vertebral column.
Anterior longitudinal ligament.
Terminal parts of hemiazygos and hemiazygos veins.
Right posterior intercostal arteries.
To the right:
Azygos vein.
To the left:
Descending thoracic aorta. Thoracic Duct MBBSPPT.COM 16<br>
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In The Superior Mediastinum,
Anterior:
Arch of aorta.
Commencement of left subclavian artery.
Posterior:
Vertebral column.
To the right:
Edge of esophagus.
To the left:
Lung and pleura. Thoracic Duct MBBSPPT.COM 18<br>
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In The Root Of The Neck,
Anterior:
Carotid sheath consisting of left common carotid artery, left internal jugular vein, and left vagus nerve.
Posterior:
Vertebral artery and vein.
Scalenus anterior muscle (medial border).
Phrenic nerve.
Thyrocervical trunk and its branches (example: suprascapular, transverse cervical, and inferior thyroid arteries). Thoracic Duct MBBSPPT.COM 19<br>
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The thoracic duct terminates in the junction between the left internal jugular and the left subclavian veins.
Near its junction with the venous system it is joined by:
The left jugular trunk, which drains lymph from the left side of the head and neck;
The left subclavian trunk, which drains lymph from the left upper limb;
Occasionally, the left broncho mediastinal trunk, which drains lymph from the left half of the thoracic structures. TRIBUTARIES MBBSPPT.COM 21<br>
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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 broncho mediastinal trunk. Thoracic Duct (The tributaries) MBBSPPT.COM 22<br>
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There are 3 stages in the development of the thoracic duct.
Stage I: In this phase, network of lymph channels is observed in front of the thoracic part of the vertebral column.
Stage II: In this phase, 2 longitudinal lymph channels appear, in the network of lymph channels, 1 on the left and another on the right using a number of cross communications.
Stage III: In this phase, the cross communication appears opposite the T5 vertebra, right longitudinal channel below this cross communication and left longitudinal channel above this cross communication persists and create the thoracic duct. All the other parts disappear. DEVELOPMENT MBBSPPT.COM 23<br>
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The thoracic duct is thin walled and might be colorless, for that reason, it ts sometimes injured inadvertently 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 named chylothorax.
The cervical part of thoracic duct could be damaged during block dissection of the neck. It ought to be ligated immediately. If ligated, the lymph returns by anastomotic channels.
Otherwise it might chylous fistula and leakage of lymph. INJURY OF THORACIC DUCT MBBSPPT.COM 24<br>
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Sometimes in filarial infection, the thoracic duct is obstructed by microfilarial parasites (wuchereria bancrofti) leading to widespread effects:
Chylothorax,
Chyloperitoneum,
Chyluria,
The accumulation of chyle in the tunica vaginalis (chylocele). OBSTRUCTION OF THORACIC DUCT MBBSPPT.COM 25<br>
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Thank You MBBSPPT.COM 26<br>
