Anatomy and histology of the lower urinary tract

The function of the lower urinary tract is basically storage of urine in the bladder and the at-will periodic evacuation of the stored urine. Urinary incontinence is one of the most common lower urinary tract disorders in adults, but especially in the elderly female. The urethra, its sphincters, and the pelvic floor are key structures in the achievement of continence, but their basic anatomy is little known and, to some extent, still incompletely understood. Because questions with respect to continence arise from human morbidity, but are often investigated in rodent animal models, we present findings in human and rodent anatomy and histology. Differences between males and females in the role that the pelvic floor plays in the maintenance of continence are described. Furthermore, we briefly describe the embryologic origin of ureters, bladder, and urethra, because the developmental origin of structures such as the vesicoureteral junction, the bladder trigone, and the penile urethra are often invoked to explain (clinical) observations. As the human pelvic floor has acquired features in evolution that are typical for a species with bipedal movement, we also compare the pelvic floor of humans with that of rodents to better understand the rodent (or any other quadruped, for that matter) as an experimental model species. The general conclusion is that the "Bauplan" is well conserved, even though its common features are sometimes difficult to discern

Intraluminal pressure changes in vivo in the middle and distal pig ureter during propagation of a peristaltic wave

Intraluminal pressure changes in vivo in the middle and distal pig ureter during propagation of a peristaltic wave. Roshani H, Dabhoiwala NF, Dijkhuis T, Lamers WH. Department of Urology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. OBJECTIVES: To establish the characteristics of mechanical activity during ureteral peristalsis and unidirectional bolus transport, pressure changes in the middle and distal (juxtavesical and ureterovesical junction) porcine ureter were quantified in vivo. METHODS: Five female New Yorkshire pigs (50 to 60 kg) were studied under halothane anesthesia. The endoscopic approach was used to position an 8-channel 6 F perfusion catheter under direct vision into the distal ureter by way of the orifice. Ureteral activity was studied in two separate sessions at 1-week intervals. The pressure, propagation velocity, and length of the peristaltic waves were analyzed. RESULTS: The average maximal pressure in a not previously instrumented ureter amounted to 35.7 +/- 1.2 cm H(2)O in the mid-ureter, and decreased to 19.4 +/- 1.3 cm H(2)O in the juxtavesical ureter (P < 0.001) and further to 7.2 +/- 1.0 cm H(2)O (P < 0.001) in the submucosal segment. The propagation velocity of the peristaltic wave through the ureter was 2.1 +/- 1.3 cm/s. The length of the pressure peak was 5.9 +/- 1.6 cm. CONCLUSIONS: A ureteral peristaltic contraction wave travels at approximately 2 cm/s and is approximately 6 cm long. It is responsible for the unidirectional transport of a urinary bolus and itself acts as an "active" antireflux mechanism. The maximal pressure in the lumen of the ureter decreased from proximally to distally, but remains sufficiently high at the ureterovesical junction to prevent retrograde urine leakage when the ureter empties its urinary bolus into the bladder and the orifice is ope

Innervation of the pelvic floor muscles: a reappraisal for the levator ani nerve

OBJECTIVE: We investigated the clinical anatomy of the levator ani nerve and its topographical relationship with the pudendal nerve. METHODS: Ten female pelves were dissected and a pudendal nerve blockade was simulated. The course of the levator ani nerve and pudendal nerve was described quantitatively. The anatomical data were verified using (immuno-)histochemically stained sections of human fetal pelves. RESULTS: The levator ani nerve approaches the pelvic-floor muscles on their visceral side. Near the ischial spine, the levator ani nerve and the pudendal nerve lie above and below the levator ani muscle, respectively, at a distance of approximately 6 mm from each other. The median distance between the levator ani nerve and the point of entry of the pudendal blockade needle into the levator ani muscle was only 5 mm. CONCLUSION: The levator ani nerve and the pudendal nerve are so close at the level of the ischial spine that a transvaginal "pudendal nerve blockade" would, in all probability, block both nerves simultaneously. The clinical anatomy of the levator ani nerve is such that it is prone to damage during complicated vaginal childbirth and surgical interventions

Lack of specificity of commercially available antisera against muscarinergic and adrenergic receptors

Commercially available antisera against five subtypes of muscarinic receptors and nine subtypes of adrenoceptors showed highly distinct immunohistochemical staining patterns in rat ureter and stomach. However, using the M1-4 muscarinic receptor subtypes and alpha(2B)-, beta(2)-, and beta(3)-adrenoceptors as examples, Western blots with membranes prepared from cell lines stably expressing various subtypes of muscarinic receptors or adrenoceptors revealed that each of the antisera recognized a set of proteins that differed between the cell lines used but lacked specificity for the claimed target receptor. We propose that receptor antibodies need better validation before they can reliably be used

The contribution of the levator ani nerve and the pudendal nerve to the innervation of the levator ani muscles; a study in human fetuses.

OBJECTIVES: The contributions of the pudendal and levator ani nerves to the innervation of the levator ani muscle (LAM) are disputed. Because of the relatively large size of the nerves in early life, we investigated this issue in human fetuses. METHODS: (Immuno)histochemically stained serial sections of nine human fetuses (9-22 wk of gestation) were investigated. Both the left and right sides of the fetal pelves were studied individually and 3D reconstructions were prepared. RESULTS: The levator ani nerve innervated the LAM in every pelvis, whereas a contribution of the pudendal nerve to the innervation of the LAM could be demonstrated in only 10 pelvic halves (56%). In 10 halves, we observed a communicating nerve branch between the pudendal and levator ani nerves that pierced the pelvic floor between the LAM and the coccygeus muscle. No sex differences were observed, but the innervation pattern did differ between the left and right side of a pelvis. CONCLUSIONS: The LAM often has a dual somatic innervation with the levator ani nerve as its constant and main neuronal supply