The plasma in the artery flows along the arteryblood capillaryAt the end of the artery, many substances will enter the tissue fluid through the capillary wall.
Capillaries are the smallest and most widely distributed vessels.They branch and mesh with each other.Within organs and tissuesCapillary networkThe density of the tissues and organs with strong metabolism are as followsskeletal muscle、myocardium, lung, kidney and many glands, the capillary network is very dense;Tissue with low metabolism, such as bonetendonandLigamentThe capillary network is sparse.
structure
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The capillary diameter is generally 6-8 μ m,Blood sinusLarger, with a diameter of 40 μ m.The capillary wall is mainly composed of one layerendothelial cellsandBasement membraneform.The thin capillary is surrounded by an endothelial cell on the cross section, and the thickerblood capillaryIt is surrounded by 2-3 endothelial cells.There is a little connective tissue outside the basement membrane of endothelial cells.In endothelial cells andBasement membraneThere is a kind of flat and protuberant cell scattered between them, and the cell protuberance clings to the base of endothelial cell, calledPericyte（pericyte）。PericyteIts function is still unclear, some people think that it mainly plays a mechanical support role;Others believe that they are undifferentiated cells, which candifferentiationbysmooth muscleFiber andFibroblast。
