Thoracic duct

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Thoracic duct

In human anatomy

Anatomy

Anatomy is a branch of biology that is the consideration of the body plan. It is a general term that includes human anatomy, animal anatomy and plant anatomy ....
, the thoracic duct (aka left lymphatic duct) is an important part of the lymphatic system

Lymphatic system

The lymphatic system in vertebrates is a network of conduits that carry a clear fluid called lymph. It also includes the lymphoid tissue through which the lymph travels....
—it is the largest lymphatic vessel in the body. It is also known under various other names including the alimentary duct, chyliferous duct, duct of Pecquet, the left lymphatic duct and Van Hoorne's canal.

It collects most of the lymph

Lymph

Lymph is the fluid that is formed as the interstitial fluid. It enters the lymph vessels by filtration. The lymph then travels to at least one lymph node before emptying ultimately into the right or the left subclavian vein, where it mixes back with blood....
in the body (except that from the right arm and the right side of the chest, neck and head, and lower left lobe of the lung, which is collected by the right lymphatic duct

Right lymphatic duct

The right lymphatic duct, about 1.25 cm. in length, courses along the medial border of the Scalenus anterior at the root of the neck. In most cases it ends in the right subclavian vein, at its angle of junction with the right internal jugular vein, although the termination can be variable....
) and drains into the systemic (blood) circulation

Circulatory system

The circulatory system is an organ that moves nutrients, gases, and wastes to and from cells to help fight diseases and help stabilize body temperature and pH to maintain homeostasis....
at the left subclavian vein

Subclavian vein

In human anatomy, the subclavian veins are two large veins, one on either side of the body. Its diameter is approximately that of a man's small finger....
.

dults, the thoracic duct is typically 38-45cm in length and an average diameter of about 5mm.

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Location

In adults, the thoracic duct is typically 38-45cm in length and an average diameter of about 5mm. It usually starts from the level of the second lumbar vertebra and extends to the root of the neck

Neck

The neck is the part of the body on many limbed vertebrates that distinguishes the head from the torso or trunk. The scientific term signifying "of the neck" is nuchal....
.

It originates in the abdomen

Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity....
from the confluence of the right and left lumbar trunk and the intestinal trunk, forming a significant pathway upward called the cisterna chyli

Cisterna chyli

The cisterna chyli is a dilated sac at the lower end of the thoracic duct into which lymph from the intestinal trunk and two lumbar lymphatic trunks flow....
.

It extends vertically in the chest and curves posteriorly to the left carotid artery and left internal jugular vein

Internal jugular vein

The two internal jugular veins collect the blood from the brain, the superficial parts of the face, and the neck....
at the C7 vertebral level to empty into the junction of the left subclavian vein and left jugular vein

Jugular vein

The jugular veins are veins that bring deoxygenated blood from the head back to the heart via the superior vena cava....
, below the clavicle

Clavicle

In human anatomy, the clavicle or collar bone is classified as a flat bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is Abduction ....
, near the shoulders

Shoulders

Shoulders is drinking game that involves players competing in a fast paced game attempting to "count" to 21....
.

It traverses the diaphragm at the aortic aperture and ascends the posterior mediastinum

Posterior mediastinum

The posterior mediastinum is an irregular triangular space running parallel with the vertebral column....
between the descending thoracic aorta

Thoracic aorta

The thoracic aorta is contained in the posterior mediastinal cavity.It begins at the lower border of the fourth thoracic vertebra where it is continuous with the aortic arch, and ends in front of the lower border of the tenth thoracic vertebra, at the aortic hiatus in the diaphragm where it becomes the abdominal aorta....
(to its left) and the azygos vein

Azygos vein

The azygos vein is a vein running up the right side of the thoracic vertebral column. It can also provide an alternate path for blood to the superior vena cava....
(to its right).

Volume, mechanism, and direction of flow

In adults, the thoracic duct transports up to 4 L of lymph per day.

The lymph transport in the thoracic duct is mainly caused by the action of breathing, aided by the duct's smooth muscle

Smooth muscle

Smooth muscle is a type of non-striated muscle, found within the tunica media layer of large and small arteries and veins, the urinary bladder, uterus, male and female reproductive tracts, gastrointestinal tract, respiratory tract, the ciliary muscle, and iris of the eye....
and by internal valve

Valve

A valve is a device that regulates the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe Piping and plumbing fittings, but are usually discussed as a separate category....
s which prevent the lymph from flowing back down again.

There are also two valves at the junction of the duct with the left subclavian vein, to prevent the flow of venous blood into the duct.

Clinical significance

When the thoracic duct is blocked or damaged a large amount of lymph can quickly accumulate in the pleural cavity

Pleural cavity

In human anatomy, the pleural cavity is the body cavity that surrounds the lungs. The lungs are surrounded by the pleurae, a serous membrane which folds back upon itself to form a two-layered, membrane structure....
, this situation is called chylothorax

Chylothorax

A chylothorax is a type of pleural effusion. It results from lymphatic fluid accumulating in the pleural cavity....
.

The first sign of a malignancy (especially an intraabdominal one) may be an enlarged Virchow's node

Virchow's node

In medicine , Virchow's node is an enlarged, hard, left clavicle lymph node which can contain metastasis of visceral malignancy....
, a lymph node

Lymph node

A Lymph node is an organ consisting of many types of cells, and is a part of the lymphatic system. Lymph nodes are found all through the body, and act as filters or traps for foreign particles....
in the left supraclavicular area, in the vicinity where the thoracic duct empties into the left subclavian vein.

Additional images

External links

- "The thoracic duct and azygos venous network."

Thoracic duct

Location

Volume, mechanism, and direction of flow

Clinical significance

Additional images

See also

External links