In multicellular organisms, and particularly in mammals, both gonadal and
germ cell development are essential for the transmission of genetic information to the
next generations. The testes are paired ovoid organs located inside the scrotum but
outside the abdominal cavity. They have two major functions: spermatogenesis and
steroidogenesis. The former corresponds to the production of male gametes,
spermatozoa; the latter, to the production of hormones that will influence
spermatogenesis and consequently male reproductive function and health. The male
and female reproductive organs have the same precursor tissues. Initially, the embryo
has a bipotential gonad which may have a testicular or ovarian fate. Accordingly,
Müllerian ducts form the uterus and fallopian tubes in females and Wolffian ducts form
the epididymis, vas deferens, and ejaculatory duct in males. On the other hand, male
sex determination is triggered by sex-determining region Y (SRY), which is located on
the Y chromosome and works as a master regulator, initiating SOX9 expression. The
latter causes urogenital development, a highly complex process, through a complex
cascade of transcription factors and signaling events. These will promote testis
differentiation and ultimately the production of hormones that will lead to male
development and testicular function during adulthood. In this chapter, we will provide
a brief overview of the testicular anatomy and functional organization, as well as its
embryonic development.
Keywords: Genital ridge, Interstitial compartment, Leydig cells, Male
reproductive tract, Peritubular myoid cells, Prenatal development, Pre-Sertoli
cells, Sex-determining region Y, Sex differentiation, Testis cords, Tubular
compartment.
