The Differences And Resemblances Of The Structure Of Urinary Sphincter Between Female Fischer344Rats And Human Female

Objective: To settle the mechanism of women urinary continence, one couldpotentially rely on epidemiological or clinical studies. However, the inherentlimitations of clinical studies do not enable the investigation of mechanisticcause-and-effect relationships under controlled conditions. So an animal model thatshares the biological characteristics of the human condition is the only workablealternative for investigating the mechanism. And experiments are often performed inanimal models especially mammals. Researchers often choose rats as the animalmodels. But before apply the results of animal model studies to the humans, it isnecessary to attain a clear knowledge of the comparative anatomy of both species. Soour experiment is about detailed comparative studies of the lower urinary tract of thefemale Fischer344rats and the human female, to demonstrate anatomicalcorrespondences and differences between both species.Methods: We investigated the lower urinary tract anatomy of9female Fischer344rats and two human female by serial sections. Each one of urinary tract was dividedinto three parts: proximal，middle and distal, stained with Masson’S trichrome，Amicroscope was used to observe and describe the microstructure and the spatialconformation of the urethra．Results: The resemblances: Both the urethra of human female and female Fischer344rats can be divided into Three parts according to histology: the Proximal, the Middle, and the Distal. From inside to outside, the Proximal comprise: the circular smoothmuscle layer, dense connective tissue and mucosa. The urinary lumen isfunnel-shaped at this part, so we named the Proximal “funnel-shaped urethra”. Thestructure of the Middle is different from the Proximal, from outside to inside, there areΩ-shape striated muscle fiber, circular and longitudinal smooth muscle, denseconnective tissue and mucosa, the urinary lumen is slit-shaped, much narrower thanthe Proximal because of the existence of the urethra ridge. The Middle is capable ofurinary continence due to its special structure, it acts like sphincter, so we name theMiddle “sphincter urethra”. From outside to inside, compare with the Middle, theDistal has less smooth muscle fiber, dense connective tissue and mucosa. The urinarylumen of the Distal is wider, ampulla-shaped, so named “ampulla-shaped urethra”.The differences: first, human female have a musculus sphincter vesicae, which isnot found in rats; secondly, the distribution of muscle fiber of human female urinarytract is different from the rat’s, we mark the bladder neck as0%, and the externalmeatus as100%, the striated muscle fiber can be found in20%-80%in human female,and smooth muscle fiber is almost0%to100%; In Fischer344rats, the striatedmuscle fiber spread from10%to70%, smooth muscle fiber range from0%to80%.Conclusions: There is a degree of resemblance between the anatomic structure oflower urinary tract of female Fischer344rats and female human, they are suitableanimal models to simulate women. Suggest that physiological interpretations ofurethral functions in respect to urinary continence obtained in one specie can be partlyattributed to humans.