Q.Describe the histological structure of a seminiferous tubule.

[!TLDR]

A seminiferous tubule's wall is a germinal epithelium of germ cells at successive stages of spermatogenesis interspersed with supporting Sertoli cells, with hormone-secreting Leydig cells in the surrounding interstitial tissue.

[!ANSWER]

Germinal epithelium (spermatogonia to spermatids) + Sertoli cells inside the tubule; Leydig cells in the interstitial tissue outside it.

In transverse section, a seminiferous tubule shows a thick, multi-layered germinal (spermatogenic) epithelium surrounding a central lumen. Germ cells are arranged in concentric layers reflecting successive stages of spermatogenesis, from spermatogonia against the basement membrane through primary and secondary spermatocytes to spermatids nearest the lumen. Interspersed among them, running from the base to the lumen, are tall Sertoli cells, which nourish and support the germ cells and are the target of FSH. Outside the tubule's boundary wall, in the interstitial connective tissue between adjacent tubules, lie clusters of Leydig cells, which secrete testosterone under LH stimulation.

[!ANSWER]

Germinal epithelium (spermatogonia to spermatids) + Sertoli cells inside the tubule; Leydig cells in the interstitial tissue outside it.

Describe the tubule wall from base to lumen (successive germ-cell stages plus Sertoli cells), then describe what lies outside the tubule (Leydig cells in interstitial tissue) -- an inside-then-outside structure.

Placing Leydig cells inside the seminiferous tubule wall alongside the germ cells and Sertoli cells -- Leydig cells actually lie outside the tubule, in the interstitial tissue between tubules.