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 formsthe albuginea. The wall of these cords thickens, it is made up of cells derived from theblastema, 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, whichunites 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 theconnection between the rete testis and the Wolffian canal, they constitute the efferent conesof the testicle. The Wolffian canal persists and is at the origin of most of the male genitaltract: The short segment located above the efferent cones is the only one to regress, itscephalic 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 bodyof the epididymis. The segment located below the efferent cones keeps a path sinuous and fills the tail of theepididymis The caudal part takes a rectilinear path, is surrounded by a wall thick andbecomes the vas deferens. Muller's canal regresses almost completely, only persists itscephalic 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 posteriorwall of the urogenital sinus opposite the müllerian tubercle remain very reduced in the malesex; they form a small cavity, the prostatic utricle, while the müllerian tubercle persists in theform 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 the10th 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 endof the 3rd month to buds which develop in the mesenchyme which surrounds it. These budswill continue to develop during fetal life into the glandular units of the prostate. During thisproliferation 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. Thissegment of the Wolffian canal located below the mouth of the seminal vesicle will becomethe ejaculatory duct which follows the vas deferens. These accessory glands of the male genital tract will become functional after puberty, theirsecretions 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 locatedabove the junction of the ejaculatory ducts, it becomes urogenital below this junction as inthe rest of its course; the underlying segment, located in the floor of the region pelvic, is called the membranousurethra, ✪ 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 junctionas 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.