Lymphatic System | Angiology | Anjani Mishra

 Written by Anjani Mishra

Lymphatic system

The term “lymphatic system” includes, in a broader sense, the descriptive and functional aspects of the lymphatic tissue structures and those of lymph system. The term lymphatics is limited to the lymph vessels.

The term “lymph vascular system” includes, the lymph capillaries, vessels, ducts and trunks, and their contents, but not the lymphnodes.

Lymph

• Lymph is a clear colourless fluid except in the intestinal vessels in which, after digestion, it is milky in colour.

• These are mainly distributed in the serous membrane, mucous membrane, synovial membrane, glands and skin.

• No lymph vessels are found in the central nervous system (except meninges), bone marrow, cornea, lens, vitreous humor of the eye, epithelial layer of the skin and other all avascular structures like hairs, nails, feather, cartilage etc.

Lymph circulation

• The lymph vessels start as “finger-like” thin walled capillaries in the connective tissue. They form a capillary networks which drains into larger and thicker walled collecting lymph vessels, lymph ducts and trunk. Ultimately the content of these trunks and ducts, the lymph empties into the cranial venacava.

• The movement of lymph from periphery to the centre is affected by pressure gradient brought about mainly by forces outside the lymphatic system. Usually the tissue pressure is greater than the pressure in the lumen of the lymph capillaries. Therefore, the pressure (lymph) in the vessels rises and the lymph moves centripedally to a region where the pressure is lower.

• Muscular activity, respiratory movement, abdominal pressure, intestinal movement etc. also provide pumping action to increase lymph flow.

Cisterna chyli

• Cisterna chyli is a dilated and elongated sac about 2-3 inches in length and 0.5 inch in thickness placed to the right side of the abdominal aorta at the level of 2^nd and 3^rd lumbar vertebrae and on the right face of the crus of diaphragm.

• It is formed by the union of lumbar and gastro-intestinal lymphatic trunks. It is the reservoir of lymph. From its cranial end the thoracic duct starts.

Thoracic duct

• This is the main lymphatic trunk which receives lymph from all parts of the body except from the right side of the head, neck, trunk and fore-limb.

• It enters the thorax through aortic aperture of diaphragm, passes forward along the right part of the dorsal face of the aorta and receives a large duct, coming from mediastinal lymph glands.

•  It then crosses the dorsal face of the esophagus and aorta to reach the left of the midline and finally terminates in the cranial venacava or left common jugular vein in front of 1^st rib.

• In the thorax, the vessels may be divided into two left and right branches which again unite at the level of 6^th thoracic vertebra.

Right lymphatic duct

• It receives lymph from right side of the head, neck, thorax and right fore-limb and opens into right common jugular vein.

Fig: schematic diagram of lymphatic system

(Note:- For more details go through the lymphatic system in Histology)

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