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The ends of the endothelial cells that make up the wall of a lymphatic capillary overlap. When pressure is greater in the interstitial fluid than in lymph, the cells separate slightly, like the opening of a one-way swinging door, and interstitial fluid enters the lymphatic capillary. When pressure is greater inside the lymphatic capillary, the ...
Lymphatic vessels develop from lymph sacs that arise from developing veins, which are derived from mesoderm. The first lymph sacs to appear are the paired jugular lymph sacs at the junction of the internal jugular and subclavian veins. From the jugular lymph sacs, lymphatic capillary plexuses spread to the thorax, upper limbs, neck, and head.
Lymph vessels are lined by endothelial cells, and have a thin layer of smooth muscle, and adventitia that binds the lymph vessels to the surrounding tissue. Lymph vessels are devoted to the propulsion of the lymph from the lymph capillaries, which are mainly concerned with the absorption of interstitial fluid from the tissues.
It is filled with interstitial fluid, including lymph. [5] Interstitial fluid provides the immediate microenvironment that allows for movement of ions, proteins and nutrients across the cell barrier. This fluid is not static, but is continually being refreshed by the blood capillaries and recollected by lymphatic capillaries. In the average ...
Capillary walls allow the free flow of almost every substance in plasma. [6] The plasma proteins are the only exception, as they are too big to pass through. [5] The minimum number of un-absorbable plasma proteins that exit capillaries enter lymphatic circulation for returning later on to those blood vessels.
Lymph has a composition similar but not identical to that of blood plasma. Lymph that leaves a lymph node is richer in lymphocytes than blood plasma is. The lymph formed in the human digestive system called chyle is rich in triglycerides (fat), and looks milky white because of its lipid content.
The lymphatic system drains the head and neck of excess interstitial fluid via lymph vessels or capillaries, equally into the right lymphatic duct and the thoracic duct. Lymph nodes line the cervical spine and neck regions as well as along the face and jaw. The tonsils also are lymphatic tissue and help mediate the ingestion of pathogens.
A lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the small intestine. Triglycerides are emulsified by bile and hydrolyzed by the enzyme lipase, resulting in a mixture of fatty acids, di- and monoglycerides. [1] These then pass from the intestinal lumen into the enterocyte, where they are re-esterified to form ...