奶牛精子尾部主段外周致密纤维的电子显微镜观察

奶牛精子尾部主段的中央结构为轴丝。在轴丝的外方有外周致密纤维。外周致密纤维由中段延伸而来。进入主段后,9条外周致密纤维逐一终止。最早终止的是第8条纤维。随后的终止顺序是第3、7、4、2、6、5、9、1条。因此,9条外周致密纤维中,最长的是第1条纤维,最短的是第8条纤维。9条纤维按长短顺序排列依次是第1、9、5、6、2、4、7、3、8条。根据外周致密纤维数量的多寡,可以将主段分为10个区域。从近中段端至近末段端,这10个区域依次是9条、8条、7条、6条、5条、4条、3条、2条、1条、0条纤维区域。外周致密纤维的外方有一纤维鞘。纤维鞘的背侧纵柱和腹侧纵柱分别向内伸出一个嵴。在主段的0条纤维区域,纤维鞘直接位于轴丝之外。在纤维鞘的外方还有精子的细胞质膜。

ELECTRON MICROSCOPIC OBSERVATIONS ON THE OUTER DENSE FIBERS OF THE PRINCIPAL PIECE OF THE BOVINE SPERM TAIL

At the proximal end of the principal piece of bovine sperm tail, the axoneme, which is situated at the center of the tail, is encircled by nine outer dense fibers. These fibers extend from the middle piece of the tail. The outer dense fibers are numbered as follows:. Let the cross sections of the principal piece be located at a position in which the dynein arms of A tubule of one doublet point to B tubule of the adjacent doublet clockwise. Let the connecting line of the axoneme's two central single microtubules coincide with coordinate's Y axis and the middle point of the connecting line be the origin of the coordinate. The only doublet which is on X axis of the coordinate is numbered as doublet 1. The rest eight doublets are numbered clockwise as doublet 2 to doublet 9 respectively. The nine outer dense fibers are numbered the same as the corresponding doublets inside. These outer dense fibers taper and terminate one by one within the principal piece. The terminating sequence is No.8, No.3, No.7, No.4. No.2. No.6, No.5,No .9, No.l. In order of length, nine outer dense fibers are ranged as follows. No.l, No.9, No.5, No.6, No.2, No.4, No.7. No.3. No.8 Therefore the principal piece can be divided into 10 regions according to the quantity of the outer dense fibers. From the proximal end to the distal end, there is 9-fiber, 8-fiber, 7-fiber, 6-fiber, 5-fiber, 4-fiber, 3-fiber, 2-fiber. 1-fiber and 0-fiber region. Outside the outer dense fibers, there is a fibrous sheath, which consists of circumferential ribs, dorsal longitudinal column, and ventral longitudinal column. The ridges of the dorsal and ventral longitudinal columns extend inward respectively. At the distal end of the principal piece where there is no outer dense fiber, the axoneme is encircled the fibrous sheath immediately.