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Unformatted text preview: www.brain101.info 1 THE PELVIS AND THE PERINEUM Development of the Urogential Region The Pelvic Brim Rectum, Anal Canal, Ischioanal Fossae External Genitalia Vascular / Nervous Supply to the Pelvis The Perineum Pelvic Viscera Female Reproductive Organs Male Reproductive Organs Vessels of the Pelvis DEVELOPMENT OF THE UROGENITAL REGION INTERMEDIATE MESODERM: Development of the urogenital system originates from the intermediate mesoderm, one of the three mesodermal layers formed after neurulation. There are three mesodermal layers o Paraxial Mesoderm: Forms the somites + vertebral column o Lateral Plate Mesoderm: Forms the body walls o Intermediate Mesoderm: Forms the urogenital system. UROGENITAL RIDGE: Develops from the intermediate mesoderm. It forms longitudinal columns. This ridge will lead to development of the following: Gonadal Ridge: Will form the indifferent gonad ------> ovaries / testis Nephrogenic Cord: Will form the kidney Mesonephric Duct: Will form the ureter and the male genital ducts, seminal vesicles. Paramesonephric Duct: Will form the Uterine Tubes o Uterovaginal Primordium: Formed from the paramesonephric duct. It will form the uterus and part of the vagina. CLOACA: ENDODERMAL! The distal portion of the GI tube, after foregut / midgut / hindgut. It forms the following structures. It forms the Urogenital Sinus , which in turns leads to the following structures. The Urinary Bladder Urethra, Prostate Gland, Bulbourethral Glands (male) o The prostate is lobulated, coming off the pelvis portion of the UG sinus. o The bulbourethral gland als comes off the pelvic portion of the UG sinus. o The seminal vesicles do not come from UG sinus!-- they come from the mesonephric duct. Urethra, Vaginal Epithelium, Vestibular Glands, Vestibule (female) GUBERNACULUM: The primitive round ligament and ovarian ligament in the female. Developmentally, it determines the descent of the gonads in both species. It is a long, tenuous cord. o The superior end of the cord attaches to the inferior pole of the gonad to pull them down. o The inferior pole attaches to the primitive labia (scrotum), or the developing perineal region. The shrinking of the gubernaculum pulls the gonad down from the abdominal region (initially it develops as high as T10!) Processus Vaginalis = invagination in the abdominal wall, near the inferior part of the gubernaculum. o It invaginates into the labioscrotal folds. o The processus vaginalis is more prominent in the male, due top the descent of the testes through it. o Inguinal Canal forms by shrinking of the gubernaculum, dragging the processus vaginalis with it. The round ligament (female) or spermatic cord (male) go through the inguinal canal. www.brain101.info 2 o Congenital Indirect Hernia results when the processus vaginalis remains patent after birth....
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