The human body has two major circulatory systems: the blood and lymphatic systems. Although the blood vascular system and the lymphatic system operate in parallel and share some anatomical features, the two vascular systems have had very different fates in science and medicine, as they display distinct structural and functional features. While the blood system has been extensively studied and examined, the lymphatic system has been neglected and considered as less important compared with the blood system. The word lymph comes from the Latin word lymphaticus, meaning, "connected to water," as lymph is clear, nevertheless our knowledge about the lymphatic system is far from clear. Yet, in past decades, a series of landmark discoveries has unraveled
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The structure of collecting lymphatics allow such a function since the wall consist of multiple layers. In fact Three layers can be identified—the intima, media and adventitia similar to that of blood vessels. The inner most layer consists of connected LECs in zipper-like junctions and therefore the absence flap valve. LECs also surrounded with continuous basement membrane (13). Consequently, the collecting lymphatic lack the ability of absorbing interstitial fluid compared with initial lymphatic capillaries and precollecting lymphatics. The second layer consists of a muscle bundle arranged in hellicoidal fashion (7). The outermost layer is the adventitia that consists of fibrous tissue. Collecting lymphatic vessels characterized also by the presence of valves. The valve leaflets consist of collagen fibers covered only with a monolayer of LECs, and SMCls are absent from the valve leaflets. The presence of these passive valves, passive since they lack SMCs and hence propulsive contraction, preserve a unidirectional flow of the lymph from one segment of the vessel to the next one. High lymph pressure upstream of a valve opens the valve and allows lymph flow, whereas reverse flow pushes the leaflets against each other and closes the valve …show more content…
The mucosa are folded in a structures called villi to increase surface area of absorption. Each villi contain a bundle of lymphatic capillaries consist of single sac-like vessels called lacteal. Lacteal, which has the same structure of initial lymphatics and occupy the centers of the villi, consist of non-fenestrated single layer of LECs, with no basement membrane, compared with blood capillaries. Despite the fact the lacteal lacks fenestrations, chylomicrons are transported through the wide junctions between LECs. At the base of the villi, lacteals are connected to submucosal lymphatics. Hence the main function of lacteal is transport lymph to the submucosal lymphatics. Lacteal does not contain smooth muscle layer and therefore they lack the ability to contract spontaneously.
The submucosa layer consists of dense or loose connective tissue. All blood vessels, nerves and lymphatic vessels that supply mucosa are run through submucosa. Similar to the lacteal, the submucosal lymphatics consist of single lymphatic endothelial cells and also lack the smooth muscle
The structure of collecting lymphatics allow such a function since the wall consist of multiple layers. In fact Three layers can be identified—the intima, media and adventitia similar to that of blood vessels. The inner most layer consists of connected LECs in zipper-like junctions and therefore the absence flap valve. LECs also surrounded with continuous basement membrane (13). Consequently, the collecting lymphatic lack the ability of absorbing interstitial fluid compared with initial lymphatic capillaries and precollecting lymphatics. The second layer consists of a muscle bundle arranged in hellicoidal fashion (7). The outermost layer is the adventitia that consists of fibrous tissue. Collecting lymphatic vessels characterized also by the presence of valves. The valve leaflets consist of collagen fibers covered only with a monolayer of LECs, and SMCls are absent from the valve leaflets. The presence of these passive valves, passive since they lack SMCs and hence propulsive contraction, preserve a unidirectional flow of the lymph from one segment of the vessel to the next one. High lymph pressure upstream of a valve opens the valve and allows lymph flow, whereas reverse flow pushes the leaflets against each other and closes the valve …show more content…
The mucosa are folded in a structures called villi to increase surface area of absorption. Each villi contain a bundle of lymphatic capillaries consist of single sac-like vessels called lacteal. Lacteal, which has the same structure of initial lymphatics and occupy the centers of the villi, consist of non-fenestrated single layer of LECs, with no basement membrane, compared with blood capillaries. Despite the fact the lacteal lacks fenestrations, chylomicrons are transported through the wide junctions between LECs. At the base of the villi, lacteals are connected to submucosal lymphatics. Hence the main function of lacteal is transport lymph to the submucosal lymphatics. Lacteal does not contain smooth muscle layer and therefore they lack the ability to contract spontaneously.
The submucosa layer consists of dense or loose connective tissue. All blood vessels, nerves and lymphatic vessels that supply mucosa are run through submucosa. Similar to the lacteal, the submucosal lymphatics consist of single lymphatic endothelial cells and also lack the smooth muscle