Friede R L, Brzoska J, Hartmann U
Department of Neuropathology, University of Göttingen, Federal Republic of Germany.
J Anat. 1985 Dec;143:103-13.
The rabbit phrenic nerve was studied at seven phases of growth from the newborn to the adult to determine the length of the nerve fibres, the length of the internodes, the fibre calibre, the geometric proportions of the internodes and the thickness of the myelin sheaths. The elongation of the internodes corresponded precisely to the elongation of the nerve, indicating a constant number of approximately 140 internodes per fibre, each internode elongating commensurate with body growth. Internode elongation was accompanied by increases in fibre calibre, but these parameters did not change in precise proportion. The internodes of thick fibres were relatively short for calibre, as defined by the length/diameter quotient. This trend of foreshortening changed during growth. Sheath thickness, defined by the quotient axon diameter/fibre diameter, was determined with a computer-assisted method. Fibres of young rabbits had relatively thin sheaths for axon calibre, compared with adult rabbits. The changes in sheath thickness corresponded to the changes in internode geometry. This was consistent with previous studies showing that elongation or foreshortening of an internode of a given calibre has a slight, but definite effect on the thickness of its myelin sheath.
对从新生兔到成年兔生长的七个阶段的膈神经进行了研究，以确定神经纤维的长度、节间长度、纤维直径、节间的几何比例以及髓鞘厚度。节间的伸长与神经的伸长精确对应，表明每根纤维大约有140个节间，每个节间随着身体生长而伸长。节间伸长伴随着纤维直径的增加，但这些参数并非精确成比例变化。粗纤维的节间相对于直径而言较短，由长度/直径商来定义。这种缩短趋势在生长过程中发生了变化。通过计算机辅助方法确定了由轴突直径/纤维直径商定义的髓鞘厚度。与成年兔相比，幼兔的纤维对于轴突直径而言具有相对较薄的髓鞘。髓鞘厚度的变化与节间几何形状的变化相对应。这与先前的研究一致，先前研究表明给定直径的节间伸长或缩短对其髓鞘厚度有轻微但确定的影响。
