Muscle systems of the lower urinary tract of the male rhesus monkey (Macaca mulatta): histomorphology and 3-dimensional reconstruction.

PURPOSE: The structure and function of the lower urinary tract are still a subject of controversial discussion. Experiments in various animals, including rhesus monkeys, are often performed to improve the understanding of human physiology without adequate knowledge of anatomical differences. Therefore, a detailed study of the lower urinary tract of the male rhesus monkey (Macaca mulatta) was performed to elucidate anatomical correspondences in rhesus monkeys and humans.
MATERIALS AND METHODS: Lower urinary tract anatomy and histomorphology were investigated in male rhesus monkeys on serial sections. To differentiate striated and smooth muscle immunohistochemical staining was done. Three-dimensional reconstructions were developed to demonstrate the topography of the muscle systems.
RESULTS: We identified certain systems, including detrusor musculature extending on the bladder neck, a ventral longitudinal muscle system of the bladder neck, continuation of the musculature of the ureters to the verumontanum, a urethral sphincter consisting of a striated and a smooth muscle part, musculature between the urethra and rectum, and a striated longitudinal muscle system ventral to the urethral sphincter. The prostate gland of the rhesus monkey does not encircle the urethra but is attached dorsolateral. The internal sphincter (musculus sphincter vesicae) of humans does not exist in the rhesus monkey. The longitudinal systems of the urethra differ significantly from those in humans.
CONCLUSIONS: Due to significant differences in lower urinary tract anatomy the suitability of the male rhesus monkey seems limited as an animal model for humans. It is not suitable for studying the longitudinal muscle systems of the human bladder neck.