Disposition of the striated urethral sphincter and its relation to the prostate in human fetuses

Abstract

Objective: To describe the arrangement of the muscle fibers of the striated urethral sphincter and its relationship with the prostate during the fetal period in humans. Materials and Methods:We analyzed 17 prostates from well preserved fresh human fetuses ranging in age from 10 to 31 weeks postconception (WPC). Transversal sections were obtained and stained with Gomori's trichrome and immunolabeled with anti alpha-actin antibody. Results: We found that the urethral striated sphincter (rabdosphincter) is located on the periphery of the smooth muscle and there was no merge between striated and smooth muscle fibers in any fetal period. In the prostate apex, the striated sphincter shows a circular arrangement and covers completely the urethra externally, whereas adjacent to verumontanum, it looks like a "horseshoe" and covers only the anterior and lateral surfaces of the urethra. Near the bladder neck, in fetuses younger than 20 WPC, we have found striated muscle fibers only at the anterior surface of the prostate, while in fetuses older than 20 WPC, the striated muscle covers the anterior and lateral surfaces of the prostate. Conclusions: The urethral sphincter muscle covers the anterior and lateral surfaces of the urethra in all fetuses older than 20 WPC, close to the bladder neck and at the distal prostate. In the region of the prostate apex, the urethral sphincter covers completely the urethra circularly. The knowledge of the normal anatomy of the urethral sphincter in fetuses could be important to understand its alterations in congenital anomalies involving the base of the bladder, the bladder neck and the proximal urethra.

Genitourinary dysfunction in male rats after bilateral neurectomy of the motor branch of the sacral plexus

“…Simultaneous denervation of BC, IC and EUS, and species differences between man and rat genitourinary tract anatomy (man does not have coagulant sexual glands and the EUS covers part of the prostate)22, 23 and physiology (EUS does not discharge during voiding in men)24 limited us to determine the control of each muscle on the urinary function and to extrapolate the result to humans. However, it is important to recognize that damage to BS and IC muscle has been considered a factor for sexual (erectile and ejaculatory) and micturition (postmicturition dribbling) dysfunction in men 25…”

The position of the testis during the fetal period: an additional parameter to estimate fetal weight

“…All measurements were performed by the same investigator. The gestational age of the fetuses was determined in weeks post conception, according to the foot length criteria, which currently is the most acceptable method to estimate the fetal age (7)(8)(9)(10).…”