The testis

Abstract

The mammalian testis has two basic compartments: the interstitial (intertubular) compartment and the seminiferous tubule compartment (Fig. 1A). The interstitial compartment is highly vascularized and contains Leydig cells clustered near or around the vessels. These cells are responsive to luteinizing hormone (LH) and secrete testosterone, which subsequently accumulates in the interstitium and the seminiferous tubules at relatively high concentrations. The Leydig cell possesses abundant smooth endoplasmic reticulum (SER) and mitochondria, both of which contain the enzymes associated with steroid biosynthesis (Fig. 1B). The seminiferous tubule compartment contains Sertoli cells and developing and mature germ cells. The formation of spermatozoa from stem spermatogonia (spermatogenesis) includes mitotic and meiotic division, followed by cellular differentiation (spermiogenesis). Thus, the two major areas of activity within the testis center on steroidogenesis and spermatogenesis. A large body of literature provides evidence that LH (via stimulation of testosterone) and follicle-stimulating hormone (FSH) are the key regulators of spermatogenesis. © 2005 Humana Press Inc.