Testis and spermatogenesis - Examine the preserved-mounted specimens of testes and vas deferens, noting the macroscopic features (lobes, tubules, etc.) for correlation with these structures on the slides.

Examine both the trichrome-stained section of testis (slide 55) and the H&E stained testis (slide 119). Identify the capsule (tunica albuginea), interstitial tissue or stroma (which is not very well preserved in slide 55), and the seminiferous tubules (Fig. 18.3 and 18.4).

What constitutes the parenchyma of the testis?

Clinical note: Failure of the testes to descend into the scrotum during fetal development (cryptorchidism) maintains their temperature at 37oC which inhibits spermatogenesis, although testosterone production can still occur. Excessive blood flow or dilated vasculature in the scrotum (varicocoele) is another potential cause of male infertility and can be surgically corrected.

Study the schematic diagram (next page) of spermatogenesis and its relationship to the sustentacular Sertoli cells. On slide 155 examine the cells inside a seminiferous tubule and distinguish their interrelationships during spermatogenesis. In a tubule cut transversely, identify myofibroblasts (myoid cells), Sertoli cells (with nucleoli), spermatogonia, and the large primary spermatocytes (Fig. 18.5). The smaller secondary spermatocytes are much more short-lived and therefore more difficult to find. (Do not spend time looking for these.) Identify spermatids and differentiating spermatozoa. Try to distinguish some of the morphological stages and changes that occur in the differentiating spermatids during spermiogenesis (Fig. 18.6) and study the ultrastructure of a mature spermatozoon (Fig. 18.7).

Describe the process of meiosis and the cellular changes during spermatogenesis.

Sketch the changes a spermatid undergoes during spermiogenesis.

More about the testis.