University:
Stanford University
Course:
MED 101 | Human Anatomy
Academic year:

2023
Views:

379

Pages:

1
Author:

larbi43100

Undifferentiated external genitalia Before the 7th week, the cloacal membrane is surrounded by a rim, the cloacal fold, projecting in its ventral part where it constitutes the cloacal eminence. After the partitioning of the cloaca and the development of the perineum, the membrane is divided into two zones, anal membrane and urogenital membrane, each surrounded by its bulge. The rim circumscribing the urogenital membrane gives the genital fold on each side and the cloacal eminence becomes the genital tubercle. Laterally, mesenchymal proliferation raises the ectodermal covering and determines the formation of the labioscrotal folds. 1. The gubernaculum During the 7th week, the retroperitoneal mesenchyme condenses and forms a fibrous cord, the gubernaculum, which connects the lower pole of the gonad to the labio-scrotal folds. 2. The vaginal process At the same period of development there appears an evagination of the peritoneal cavity, the vaginal process, which slides along the gubernaculum and collapses the abdominal muscular wall; the muscular area which circumscribes the vaginal process will be at the origin of the inguinal canal. 3. Malformations of the urogenital system appearing from undifferentiated stage Certain malformations of the urogenital system result from developmental anomalies occurring before sexual differentiation: ✪At the time of formation of the definitive kidneys: renal agenesis due to the absence of contact of the metanephrogenic blastema with the ureteric bud, this anomaly can be unilateral or bilateral. ✪At the time of the ascension of the kidney: ectopia (position anomaly) or fusion of the anlages (iron kidney on horseback). abnormalities of the course of the ureter ✪At the time of septation of the cloaca the persistence of communication between the urogenital sinus and the terminal part of the digestive tract determines the formation of fistulas whose path then depends on sexual differentiation (recto-vesical, recto-urethral or rectovaginal) ✪At the time of the formation of the trine, anomalies of the joining of the ureters into the bladder.