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. 2011 Jul 1;1(3):209–220. doi: 10.4161/spmg.1.3.17990

Figure 1.

Figure 1

Morphological and cellular features of spermatogenesis in the mammalian testis. The anatomical features of the rat testis shown here (A) share many of the feature similar to other mammalian testes including humans, and the schematic drawing shown in (B) depicts the major cellular events of spermatogenesis, namely spermatogonia/SSC self-renewal via mitosis and differentiation to type B spermatogonia, which in turn transform to preleptotene spermatocytes. Preleptotene spermatocytes are the germ cells residing in the basal compartment traverse the blood-testis barrier (BTB) at stage VIII of the epithelial cycle that enter the adluminal (apical) compartment while differentiate into leptotene, zygote and then pachytene spermatocytes in a process known as cell cycle progression. Diplotene spermatocytes eventually enter meiosis I to be immediately followed by meiosis II at stage XIV as shown in (A) to form haploid round spermatids (step I spermatids). Spermatids undergo spermiogenesis to form elongating and elongated spermatids involving 19 and 16 steps in rats and mice, respectively. Elongated spermatids transform into spermatozoa following the shredding of the residual body to be phagocytosed by the Sertoli cells to allow the release of sperm at spermiation. The fine morphological features of some of these germ cells are also depicted in (B). It is noted that the seminiferous epithelium is resting on the tunica propria, which is composed of an acellular zone namely basement membrane (a modified form of extracellular matrix) and type I collagen layer, and a cellular zone of peritubular myoid cell layer and the lymphatic microvessel. It is noted that the seminiferous epithelium is composed of only Sertoli and germ cells without the presence of any blood vessels and nerve fibers since all microvessels are restricted to the interstitial space between seminiferous tubules. The BTB also physically divides the seminiferous epithelium into the basal and adluminal (apical) compartments. Different cancer/testis (CT) antigens are expressed throughout spermatogenesis with unique patterns of cellular expression among different types of germ cells. PLS, preleptotene spermatocyte; RS, round spermatid.