Anatomical study of the infra-montanal urethra in man

Sex differences in lower urinary tract biology and physiology

Females and males differ significantly in gross anatomy and physiology of the lower urinary tract, and these differences are commonly discussed in the medical and scientific literature. However, less attention is dedicated to investigating the varied development, function, and biology between females and males on a cellular level. Recognizing that cell biology is not uniform, especially in the lower urinary tract of females and males, is crucial for providing context and relevance for diverse fields of biomedical investigation. This review serves to characterize the current understanding of biological sex differences between female and male lower urinary tracts, while identifying areas for future research. First, the differences in overall cell populations are discussed in the detrusor smooth muscle, urothelium, and trigone. Second, the urethra is discussed, including anatomic discussions of the female and male urethra followed by discussions of cellular differences in the urothelial and muscular layers. The pelvic floor is then reviewed, followed by an examination of the sex differences in hormonal regulation, the urinary tract microbiome, and the reticuloendothelial system. Understanding the complex and dynamic development, anatomy, and physiology of the lower urinary tract should be contextualized by the sex differences described in this review.

Human rhabdosphincter cell culture: a model for videomicroscopy of cell contractions

BACKGROUND

Physiology of the human rhabdosphincter and its innervation are still a subject to controversy. A better understanding of rhabdosphincter function and anatomy might help to solve important urological problems like urinary incontinence. It was the aim of the present study to develop a human sphincter cell culture model for investigation of contraction mechanisms in vitro. METHODS AND RESULTS Cells were isolated from human rhabdosphincter tissue obtained from prostatectomy and cystoprostatectomy specimens. Cultured cells expressed typical features of striated muscle cells. By means of videomicroscopy with a time lapse videosystem cell contractions could be documented. Under control conditions without any contractile stimulant 8% of the cells were seen to contract. Cholinergic stimulation with 10 mM of acetylcholine induced a significant increase in contraction rate to 49%.

CONCLUSIONS

These results demonstrate that cholinergic stimulation triggers contraction of cultured human rhabdosphincter cells. This model might help to understand external urethral sphincter physiology and to establish new therapies for the treatment of sphincter dysfunctions. Prostate 47:189-193, 2001.

Supra and infralevator neurovascular pathways to the penile corpora cavernosa

The aim of this study was to provide a comprehensive description of both penile innervation and vascularisation. Eighty-five male cadavers were examined through gross and microscopic anatomical analysis. The pelvic nerve plexus had both parasympathetic and sympathetic roots. It was distributed to the external urethral sphincter giving rise to cavernous nerves which anastomosed in 70% of the cases with the pudendal nerve in the penile root. Accessory pudendal arteries were present in the pelvis in 70% of the cases, anastomosing in 70% of the cases with the cavernous arteries that originated from the pudendal arteries. Transalbugineal anastomoses were always seen between the cavernous artery and the spongiosal arterial network. There were 2 venous pathways, 1 in the pelvis and 1 in the perineum with a common origin from the deep dorsal penile vein. It is concluded that there are 2 neurovascular pathways destined for the penis that are topographically distinct. One is located in the pelvis and the other in the perineum. We were unable to determine the functional balance between these 2 anastomosing pathways but experimental data have shown that they are both involved in penile erection. These 2 neurovascular pathways, above and below the levator ani, together with their anastomoses, form a neurovascular loop around the levator ani.

Immunohistochemical and ultrastructural study of rhabdosphincter component of the prostatic capsule

PURPOSE

There has been no complete agreement on functional anatomy of muscular components of the urethral sphincteric mechanism, particularly in the male patient. The prostatic capsule was studied to define its histological structure and to determine whether its rhabdosphincter component (prostatocapsular rhabdosphincter) consists only of slow twitch or slow and fast twitch striated myofibers.

MATERIALS AND METHODS

We studied 11 whole prostates, including 1 obtained at autopsy and 10 by radical prostatectomy. Samples of prostatic capsule from 4 operative specimens were studied by electron microscopy. Whole mount paraffin sections from transverse slices of the remaining 7 prostates were double labeled with avidin biotin conjugate immunostaining using the primary monoclonal antibodies anti-alpha smooth muscle actin plus anti-alpha sarcomeric actin (all striated myofibers) or antiskeletal myosin fast (fast myofibers only). Tissue components of the prostatic capsule, including smooth muscle and slow versus fast twitch striated myofibers, were quantified by computerized image analysis.

RESULTS

The prostatic capsule consisted of collagen, smooth muscle and striated myofibers. It varied in thickness and proportion of the 3 components among specimens, and in each in relation to transverse circumferential aspect and craniocaudal (horizontal) level of the prostate. Collagen and smooth muscle were equally important components. Striated muscle elements within the capsule consisted of fast twitch and dominant slow twitch myofibers, and were much more abundant in the caudal (distal, lower) than the cranial (proximal, upper) half of the capsule, where they were deficient ventrally (anteriorly) and dorsally (posteriorly). The prostatocapsular rhabdosphincter thus had a butterfly-like appearance, with a thick posteriorly open ring at the apex and 2 thinner, divergent leaflets tapering toward the base at the bladder neck. The fast myofiber population decreased progressively from apex to base of prostate.

CONCLUSIONS

Proof is provided for mixed slow and fast twitch myofiber structure of the prostatocapsular component of human male rhabdosphincter. Sustained (tonic) contraction of slow myofibers probably reinforces the role of urethral smooth muscle in maintaining continence during bladder filling. Swift contraction of fast myofibers that abound caudally in the capsule probably supplements urethral closure by the bulkier membranous urethral part of the rhabdosphincter in preventing leakage of urine under stress when voiding is imminent or willfully withheld.

Orthotopic urinary diversions. Preparation of the urethra and continence problem

Preparation of the urethra is a crucial surgical moment when about to carry out an orthotopic urinary diversion. Correct procedure at this stage results in an efficient residual functional urethra, necessary for guaranteeing sphincteric function in order to avoid passive incontinence (it being well-known that active incontinence, mainly at night, is instead tied to the intrinsic nature of the enteric material used for bladder replacement). The authors describe the most important surgical procedures and in particular dissection of the apex of the prostate and entero-urethral anastomosis.

Functional anatomy of the organs of micturition

The anatomy of the organs of micturition has been the subject of study for nearly 150 years. As a result of advances in techniques and methods of clinical and research investigation, studies over the past three decades have intensified and have been increasingly directed at the functional implications and significance of organ anatomy and structure. This has led to revision of many traditional ideas about micturition and the development of new viewpoints and modalities for study of its disorders. This article summarizes the evolution of our thinking and understanding of the functional anatomy of the bladder and urethra over the years, and suggests possible directions for continued clinical study and investigation.

Anatomy of the prostatic nerves

The entire prostate of a 10 year old boy was cut with a microtome in to 4300 serial slices. The nerves were stained using a monoclonal antibody called anti PS 100. All information was recorded using a computer reconstruction programme. The prostatic nerve supply is very abundant. The nerve fibers of the cranial prostate (central zone) follow a pathway parallel to the anterior surface of the seminal vesicles going towards the caudal prostate. The periurethral zone is widely innervated by nerves arising from the periphery. The caudal prostate also contains many nerve fibers of variable size. We identified many nerve fibers along the anterior surface of the seminal vesicles and surrounding the lateral aspect of the prostatic capsule. They penetrate the capsule and the whole circumference of the caudal prostate. The prostatic capsule is covered by numerous nerve fibers and ganglia, which form a true periprostatic nerve network. The urethra is supplied by numerous thick fibers of more than 30 microns in diameter.

Reflections and suggestions on the nomenclature of the prostate

The prostate has been given different and contradictory nomenclatures. The nomenclature of the normal prostatic gland must allow for the concepts of comparative anatomy, human anatomy and pathologic anatomy. The object of this study, based on a review of the literature, is to analyse the discordant terminologies, which give rise to misunderstandings, and to suggest a simple nomenclature conformant to anatomic rules and the descriptions of leading authors. It seems necessary to suggest a schema utilising the studies of comparative anatomists and the original descriptions of Albarran and correlating all this information. One must distinguish between the prostate, the prostatic gland and the periprostatic fibromuscular tissue. The central glands are those situated at the center of the prostate in the urethral wall. The prostatic glands themselves are found around the urethra. Within these glands there is a distinction between the cranial glands situated around the ejaculatory ducts, which drain above the seminal colliculus, and the caudal glands situated below the ejaculatory ducts which drain into the urethra below the colliculus. Between the wall of the urethra which contains the central glands and the peripheral glands is the transitional zone.

Impact of radical prostatectomy on the characteristics of bladder and urethra

A prospective study was done to evaluate the long-term effects of radical prostatectomy on the function of the bladder in filling and voiding. Preoperative urodynamic studies were done on 29 patients with a mean age of 62.9 +/- 5.2 years. The preoperative results show that 16 of the 29 patients demonstrated detrusor instability with maximum contractile pressures of 59 +/- 28 cm. water. Followup urodynamic assessment was done in 13 of these patients 22.9 +/- 1.1 months after surgery. Postoperatively, the maximum detrusor instability pressure did not decrease significantly (49 +/- 17 cm. water). Comparison of the operative and postoperative urodynamic characteristics of bladder filling shows that radical prostatectomy produced no significant change in the filling characteristics of the bladder in terms of bladder capacity, or volume at which sensations of fullness or urgency are reported. Voiding pressure-flow studies show a significant increase in maximum flow rate (8 +/- 1 to 13 +/- 2 ml., per second, p = 0.007), and significant decreases in maximum detrusor pressure (61 +/- 5.4 to 39 +/- 4 cm. water, p = 0.002), urethral opening pressure (45 +/- 7 to 25 +/- 4 cm. water, p = 0.004) and residual volume (150 +/- 37 to 62 +/- 43 ml., p = 0.019). Urethral profile measurements show that there was no significant change in either the maximum urethral closure pressure (94 +/- 9 to 83 +/- 9 cm. water) or external sphincter length (3.6 +/- 0.8 to 3.2 +/- 0.8 cm.). Preoperatively, the bladder neck pressures were 25 +/- 4.4 cm. water and were abolished after prostatectomy, indicating that the decrease in obstructive characteristics is due to removal of the prostate.