Mendoza Ernesto, Schmid-Schönbein Geert W
Department of Bioengineering, Whitaker Institute for Biomedical Engineering, University of California San Diego, La Jolla, CA 92093-0412, USA.
J Biomech Eng. 2003 Jun;125(3):407-14. doi: 10.1115/1.1568128.
Recent experimental evidence indicates that lymphatics have two valve systems, a set of primary valves in the wall of the endothelial cells of initial lymphatics and a secondary valve system in the lumen of the lymphatics. While the intralymphatic secondary valves are well described, no analysis of the primary valves is available. We propose a model for primary lymphatics valves at the junctions between lymphatic endothelial cells. The model consists of two overlapping endothelial extensions at a cell junction in the initial lymphatics. One cell extension is firmly attached to the adjacent connective tissue while the other cell extension is not attached to the interstitial collagen. It is free to bend into the lumen of the lymphatic when the lymphatic pressure falls below the adjacent interstitial fluid pressure. Thereby the cell junction opens a gap permitting entry of interstitial fluid into the lymphatic lumen. When the lymphatic fluid pressure rises above the adjacent interstitial fluid pressure, the endothelial extensions contact each other and the junction is closed preventing fluid reflow into the interstitial space. The model illustrates the mechanics of valve action and provides the first time a rational analysis of the mechanisms underlying fluid collection in the initial lymphatics and lymph transport in the microcirculation.
最近的实验证据表明，淋巴管有两个瓣膜系统，一组位于初始淋巴管内皮细胞壁上的初级瓣膜和淋巴管腔内的次级瓣膜系统。虽然淋巴管内的次级瓣膜已有详细描述，但尚无对初级瓣膜的分析。我们提出了一个关于淋巴管内皮细胞连接处初级淋巴管瓣膜的模型。该模型由初始淋巴管中细胞连接处的两个重叠的内皮细胞延伸部分组成。一个细胞延伸部分牢固地附着于相邻的结缔组织，而另一个细胞延伸部分不附着于间质胶原。当淋巴管压力低于相邻的组织液压力时，它可自由弯曲进入淋巴管腔。从而细胞连接处打开一个间隙，允许组织液进入淋巴管腔。当淋巴液压力高于相邻的组织液压力时，内皮细胞延伸部分相互接触，连接处关闭，防止液体回流到间质空间。该模型阐明了瓣膜作用的机制，并首次对初始淋巴管中液体收集和微循环中淋巴运输的潜在机制进行了合理分析。
