THE STRUCTURAL GRADING OF COLLAGEN FIBERS UNDER LIGHT AND ELECTRON MICROSCOPE / 解剖学报

ABSTRACT

The structure of collagen fibers in the loose and dense connective tissues, from various sources (central tendon of dog diaphragm, tentorium cerebelli of hen, pericardium of adult man, etc.) were investigated with light microscope (LM), transmitting electron microscope (TEM) with ultra thin sections cut after reembedding with epoxy resin following orientation under LM, and ultrathin section under TEM coordinated with the semithin section under LM. It was observed that (1) The logitudinal striated structure within the so called collagen fibers and the collagen fiber without the logitudinal striated structure under LM are all the closely arranged collagen fibril bundle in which the space between the fibrils is narrower than 0.2?m under TEM. So that both must belong to the same grade. (2) The collagen fibrils in vivo may be singlely dispersed, or in double, or in bundles formed from 3 to hundreds of fibrils; the space between fibrils varied closely to several ?m. (3) The diameter of collagen fibrils is genera ly 20—200 nm, but there are also thicker or thiner fibrils. According to these and other previous works, we suggest the following points on the nomenclature (1) The collagen fibril is the collagen structure which has generally the diameter of 20—200nm and the cross striations of 64—70nm along its longitudinal axis under EM It should no longer be Called the collagen microfibril. (2) The collagen fiber is the bundle which is composed of three or more closely arranging collagen fibrils bound by a small amount of cement substance. Under EM, the space between the bundles is larger than 0.2?m but the space between the fibrils within the bundle is narrower than 0.2?m. Under LM, the collagen fiber is the structure without the visible subunit filament and may branch and anastomose- each other. (3) The collection of collagen fibers should be called collagen fiber bundle. It includes the so called "collagen fibers" (old routine nomenclature) with the visible subunit filaments under LM. This nomenclature should remove the confusion on the structural grading of collagen fibers and unify the concept of collagen fiber under LM with that under EM.