Male Differentiation Educational Materials

Male differentiation 1. The gonadal anlage transforms into the testis ✪The primitive sex cords located in the center of the primordium gonad continue their proliferation and isolate themselves from the cortical zone which becomes fibrous and forms the albuginea. The wall of these cords thickens, it is made up of cells derived from the blastema, the Sertoli cells which surround the germ cells. ✪The cords take on a horseshoe shape and become the testicular cords. Connections with the mesonephros persist and constitute a network, the rete testis, which unites the ends of the testicular cords with the mesonephrotic ducts. ✪The mesenchymal elements of the blastema will constitute, between the testicular cords, the interstitial tissue in which Leydig cells differentiate, from the 8th week of development. ✪Germ cells remain at the spermatogonia stage until puberty. Only later will they transform into sperm during spermatogenesis. 2. The permanent genital tract develops from the remains of the mesonephros During regression of the mesonephros, there persists some tubules which will maintain the connection between the rete testis and the Wolffian canal, they constitute the efferent cones of the testicle. The Wolffian canal persists and is at the origin of most of the male genital tract: The short segment located above the efferent cones is the only one to regress, its cephalic part gives a non-functional remainder (see glossary), the pedunculated hydatid, The segment located opposite the efferent cones forms a numerous folds which fill the body of the epididymis. The segment located below the efferent cones keeps a path sinuous and fills the tail of the epididymis The caudal part takes a rectilinear path, is surrounded by a wall thick and becomes the vas deferens. Muller's canal regresses almost completely, only persists its cephalic end which gives a residue in contact with the testicle, the sessile hydatid. The sinovaginal bulbs which have developed at the stage undifferentiated from the posterior wall of the urogenital sinus opposite the müllerian tubercle remain very reduced in the male sex; they form a small cavity, the prostatic utricle, while the müllerian tubercle persists in the form of a small raised area, the veru montanum. 3. The urogenital sinus and the annexed glands Near its entrance into the urogenital sinus, the canal of Wolff gives birth on each side, at the 10th week, to a budding which will become the beginning of the seminal vesicle. The wall of the urogenital sinus located below the area of the trigone gives birth at the end of the 3rd month to buds which develop in the mesenchyme which surrounds it. These buds will continue to develop during fetal life into the glandular units of the prostate. During this proliferation the prostate surrounds the segment of the urogenital sinus which gave rise to it, narrows it and encompasses the utricle and the terminal part of the Wolffian ducts. This segment of the Wolffian canal located below the mouth of the seminal vesicle will become the ejaculatory duct which follows the vas deferens. These accessory glands of the male genital tract will become functional after puberty, their secretions will enter into the composition of sperm. After the development of the prostate, the urogenital sinus takes its final appearance: ✪the upper part of the vesicourethral canal becomes the bladder ✪the lower part corresponds to the male urethra which presents three segments: the segment enclosed in the prostate, the prostatic urethra, is only urinary for the part located above the junction of the ejaculatory ducts, it becomes urogenital below this junction as in the rest of its course; the underlying segment, located in the floor of the region pelvic, is called the membranous urethra, ✪the distal segment, the penile urethra, develops with the organs external genitalia at the level of the penis. ✪the segment enclosed in the prostate, the prostatic urethra, is only urinary for the part located above the junction of the ejaculatory ducts, it becomes urogenital below this junction as in the rest of its course; ✪the underlying segment, located in the floor of the region pelvic, is called the membranous urethra, ✪the distal segment, the penile urethra, develops with the organs external genitalia at the level of the penis.