Functional Anatomy and Histology of the Testis

Abstract

The human testis is a paired endocrine and exocrine organ producing sex steroid hormones and mature haploid sperm. The latter are transported into the epididymis for further maturation and storage. Especially the endocrine function requires a specific anatomical and histological structure of the testis, i.e., a special “location” of the testis outside the body in the scrotum, a sophisticated blood supply, and the development of lobes within the testis containing seminiferous tubules surrounded by the interstitial compartment. Within the seminiferous tubules, both somatic Sertoli cells and different germ cell developmental stages can be described. As “nursery cells,” Sertoli cells build up the blood-testis barrier. This is required for preventing the meiotic germ cells from the own immune system and for creating a microenvironment essential for the germ cells development. Certain hormone receptors, such as androgen and estrogen receptors, specific secretions products, such as androgen binding protein, and special structural features are provided by Sertoli cells. Most interestingly, structural features of the Sertoli cells include basal and apical ectoplasmic specializations. These are required both for blood-testis barrier formation and for linking elongated spermatids within the Sertoli cell cytoplasm until sperm release. As an important part of the functional histology of the testis, Sertoli cell structure and function will be discussed in this chapter. Additionally, stages of spermatogenesis with the different germ cell differentiation steps will be described for a broad overview of testicular histology. Within the interstitial compartment, not only well-known steroid-producing Leydig cells are present but also certain cells of the immune system (mainly macrophages), lymph and blood vessels, as well as rarely seen nerve fibers.