Wrobel K H, Schilling E, Zwack M
Cell Tissue Res. 1986;246(2):387-400. doi: 10.1007/BF00215902.
Histology and ultrastructure of the connexion of seminiferous and straight testicular tubules were studied in 58 bovine testes of 29 animals ranging from 4 to 52 weeks of postnatal development. In the 4th and 8th week seminiferous tubules are solid. Their non-germinal supporting cells possess spherical nuclei in a basal location and a great amount of granular endoplasmic reticulum. The straight tubules have a narrow lumen and a stratified epithelium rich in intercellular canaliculi. Between 20 and 25 weeks the seminiferous tubules acquire a lumen and develop a terminal segment, the tip of which (terminal plug) protrudes into the cup-shaped modification of the adjacent straight tubule. At 30 weeks the structural differentiation between seminiferous tubule proper and its terminal segment has proceeded: in the former spermatocytes and spermatids make their first appearance, and the supporting cells have transformed to Sertoli cells. In the latter the morphology of the supporting cell preserves a more primitive state. Starting from the 16th week and proceeding through the 30th week and further, the epithelium of the tubulus rectus close to the connexion with the seminiferous tubule becomes monolayered by rearrangement of its cells and advances along the basal lamina into the area of the seminiferous tubule. Those cells of the seminiferous tubule that are cut off from the basal lamina by invading rectus cells degenerate. Between 40 and 52 weeks the adult situation is principally achieved. The terminal segment of the seminiferous tubule is tripartite consisting of transitional region, intermediate portion, and terminal plug. The terminal segment is surrounded by a vascular plexus. The straight testicular tubule adjacent to the terminal segment is modified into a cup region encompassing the terminal plug, followed by a narrow stalk region, which is lined by simple columnar epithelium. Mononuclear free cells are a constant feature of the tubulus rectus epithelium in all stages of postnatal development.
对29头出生后4至52周龄动物的58个牛睾丸中曲细精管与直细精管连接部的组织学和超微结构进行了研究。在第4周和第8周时，曲细精管是实心的。其非生精支持细胞的细胞核呈球形，位于基部，含有大量颗粒内质网。直细精管管腔狭窄，上皮为复层，富含细胞间小管。在20至25周之间，曲细精管形成管腔并发育出终末段，其顶端（终末栓）突出到相邻直细精管的杯状结构中。在30周时，曲细精管本身与其终末段之间的结构分化已经进行：在前者中，出现了初级精母细胞和精子细胞，支持细胞已转化为支持细胞。在后者中，支持细胞的形态保持更原始的状态。从第16周开始，经过第30周及以后，靠近与曲细精管连接部的直细精管上皮细胞通过重排变为单层，并沿着基膜向曲细精管区域推进。那些被侵入的直细精管细胞从基膜上切断的曲细精管细胞会退化。在40至52周之间，基本上达到了成年状态。曲细精管的终末段分为三部分，由过渡区、中间部分和终末栓组成。终末段被血管丛包围。与终末段相邻的直细精管被改造成一个杯状区域，包围着终末栓，接着是一个狭窄的柄状区域，内衬单层柱状上皮。单核游离细胞是出生后发育各阶段直细精管上皮的一个恒定特征。
