Rectovaginal fascia: An important structure in pelvic visceral surgery? About its development, structure, and function

BACKGROUND

The existence, development, and function of the rectovaginal fascia has been discussed in literature. In women, a defect in the fascia leads to rectoceles and severe constipation. In pediatric textbooks for anorectal or urogenital surgery, however, it is not mentioned. Does the fascia exist in children?

METHODS

The pelvises of 31 female and, as controls, 31 male fetuses (age from 9 weeks of gestation to newborn) were plastinated. Sections (transversal, sagittal, and frontal) were stained with azure II/ methylenblue/ basic fuchsin and viewed at a magnification of 6.5x to 80x. In addition, the authors investigated macroscopically and microscopically the rectovaginal fascia in 1 fetal and 1 adult cadaver.

RESULTS

At the beginning of the fetal period the authors recognized the anlage of the rectovaginal fascia caudal from the rectouterine excavation. Later, a fascia of connective tissue develops. It is connected directly to areolar connective tissue at the dorsal wall of the vagina. Neurovascular bundles are situated ventrolaterally of the rectal wall. At the level of the anorectal flexure this fascia separates the rectum and the vagina.

CONCLUSIONS

Our investigations indicate that the rectovaginal fascia is completely developed in newborns, through differentiation of mesenchyme, which develops into a fascia. It protects different compartments and serves as an abutment to the rectal wall. Thus, it is important for adequate bowel emptying. For the surgeon it is a leading structure for preventing nerve damage of the autonomic nerve supply of the pelvic organs. It should be known, protected, and, if necessary, reconstructed.

Plasticity of the urothelial phenotype: effects of gastro-intestinal mesenchyme/stroma and implications for urinary tract reconstruction

The present study tests the hypothesis that heterotypic stromal-epithelial interactions cause phenotypic changes in urothelium. The rational for the experimental design is to simulate heterotypic stromal-epithelial interactions that are created at the anastomotic site of intestinal-bladder augmentations and internal urinary diversions where the urothelium is in direct contact with the gastro-intestinal tract tissues. Tissue recombination experiments were performed by combining 14-day embryonic rat and mouse rectal mesenchyme with urothelium from embryonic, newborn, and adult mice or rats. All tissue recombinants were grown beneath the renal capsule of athymic mouse hosts for 6-16 weeks. Analyses were performed to detect expression of uroplakins, cytokeratin 7, 14, 19 and mucin secreting epithelial cells via Periodic Acid-Schiff (PAS). The phenotype of both mouse and rat urothelium was changed to a glandular morphology under the influence of rectal mesenchyme. Immunohistochemical staining revealed a loss of the urothelial specific uroplakins and cytokeratins 7, 14, and 19 (characteristic of urothelium). Histologic analysis revealed the presence of mucin secreting glandular structures which stained positive for PAS. The urothelial transdifferentiation into glandular epithelium was not a function of epithelial age and occurred in the embryonic, newborn and adult urothelium. Likewise, rectal mesenchyme from embryonic, neonatal, and adult animals was able to induce glandular differentiation in bladder epithelium. Urothelium exhibits the plasticity to change into an intestinal like epithelium as a result of mesenchymal/stromal stimulation from the gastro-intestinal tract. This experimental result is germane to heterotypic stromal-epithelial interactions that are created in patients with urinary tract reconstructions (intestinal augmentations, de-mucosalized urothelial lined bladder patches, and internal urinary diversion such as ureterosigmoidostomies). We propose that heterotypic stromal-epithelial interactions may play a role in determining histodifferentiation of urothelial cells at the anastomotic site between bowel and bladder tissue in patients with gastro-intestinal urothelial reconstructions.

Cell apical surface area in enterocytes from chicken small and large intestine during development

The absorptive surface of epithelial cells from chicken small and large intestine was studied at the day of hatch (1 d group) and at 2 and 6 wk after hatch. The segments considered were duodenum, jejunum, ileum, cecum (proximal, medial, and distal regions), and rectum. The length, diameter, and density of microvilli as well as cell apical diameter were measured in tip-villous enterocytes by transmission electron microscopy. The results obtained showed that during development: 1) microvillus length remained constant in duodenum and jejunum and decreased in the other segments; 2) microvillus diameter increased only in the jejunum and the rectum; 3) microvillus density increased in duodenum, ileum, distal cecum, and rectum (especially from 1 d to 2 wk) and did not change in the other segments; 4) cell apical diameter did not change; 5) apical surface area increased both in the duodenum (2nd to 6th wk) and in the jejunum (1 d to 2 wk) but did not change in the ileum. In the proximal-medial cecum and in the rectum there was a decrease in apical surface, whereas no changes were observed in distal cecum. Results indicated that microvillus length and density are the variables that best explain the changes observed in apical surface that occurred during development.

Ontogeny of the endocrine cells of the intestine and rectum of sea bass (Dicentrarchus labrax L.): an ultrastructural study

Several endocrine cell types were ultrastructurally characterized during the differentiation of the intestine and rectum of sea bass (Dicentrarchus labrax L.) larvae. Only one cell type (type I) was found in the posterior region of the undifferentiated gut of 5-day-old larvae (phase I). Types V and VI were found in both the intestine and rectum, types II, III and IV in the intestine, and types VII and VIII in the rectum of 9- and 12-day-old larvae (phase II), the rectum alone showing signs of functional differentiation. In phase III larvae, in which both the intestine and rectum were differentiated, types IX, X, XI, XII, XIII, XIV and XV were found in the intestine, only types X, XI and XII being seen in the rectum. Besides these, a new cell type, XVI, was observed in the intestine of 55- and 60-day-old larvae (phase IV), in which the digestive tract was completely differentiated. The endocrine cells appearing in phases I and II showed very scarce secretory granules and the ultrastructural features of undifferentiated cells. Some endocrine cell types in the earliest developmental stages were related to some of those found later. A maturational process of the endocrine cell types paralleled the differentiation of the intestine and rectum, with an apparent increase in the number of secretory granules accompanying organelle development.

Sex-related differences in the expression of chick enterocyte butyrylcholinesterase during embryonic and post-hatching development

The butyrylcholinesterase activity of chick enterocytes was studied from day 15 in ovo up to day 90 after hatching. The activities detected in both sexes at the level of jejuno-ileum change in a parallel manner, but the activity is always higher in the female than in the male during embryonic development. After hatching, the differences are less apparent although the study of the enzyme distribution along the intestine showed sex-related variations, mainly at the level of the anterior and middle parts of jejuno-ileum in the young adult. Analysis of butyrylcholinesterase by sucrose gradient centrifugation allowed to identify two globular soluble species (G1 and G4 forms). The G4/(G1 + G4) ratio decreases during the development but this variation in the female does not parallel that observed in the male. Besides, the molecular form distribution along the intestine, studied after hatching, differs according to the sex. Taken together our results lead to hypothesize that the ontogeny and the regulation of the chick enterocyte butyrylcholinesterase depend on hormones.

The mab-9 gene controls the fate of B, the major male-specific blast cell in the tail region of Caenorhabditis elegans

The internal structures of the tail of male Caenorhabditis elegans nematodes are made by the descendants of four cells (B, Y, F, and U) which divide only in males. These cells are also present in hermaphrodites, where they have minor structural roles in the rectum. Here we show that the gene mab-9 is required for the correct development of two of these male-specific blast cells, B and F. In mutant males, the lineages of B and F resemble those of Y and U, respectively. These abnormal lineages lead to grossly defective male tails. We suggest that in mab-9 males the identities of B and F are transformed into Y and U, their respective anterior neighbors. The case for the F-to-U transformation is less strong than for the B-to-Y transformation because the wild-type lineages of F and U are very similar. Some mab-9 hermaphrodites are constipated as a result of abnormal rectal structure. This may be the result of an analogous fate transformation. mab-9 worms of both sexes are slightly uncoordinated. We propose that the fates of the four rectal cells are initially specified as two pairs (B and Y, F and U) and that the function of mab-9 in both sexes is to differentiate the posterior member of each pair from its anterior neighbor.

[Enzymatic activity of neurons of various parts of the digestive tube in postnatal ontogenesis of the rat (cytophotometric histochemical study)]

Enzymatic activity in cells of the muscular-intestinal plexus of the esophagus, duodenum and rectum has been studied cytophotometrically. Glucose-6-phosphatase dehydrogenase, NADPh-dehydrogenase, acid phosphatase, alkaline phosphatase (APh), monoamine oxidase, acetylcholine esterase (AChE) have been revealed in 19-20-day-old embryos, in 1-, 21-, 30-day-old rats and in mature rats. A high APh activity is revealed in all the groups studied; in the process of development the duodenum legs behind, concerning AChE activity. This demonstrates certain peculiarities in its mediator regime. Evidently, dyskinetic phenomena in the middle part of the gastrointestinal tract in children are connected with this. Enzymatic activity, connected with general metabolic processes, demonstrates that differentiation develops towards decreasing amount of cellular types, while the enzymes, that are connected with metabolism of the mediators, demonstrate an increasing variability of cells in the process of their differentiation.

Influence of age and sex on anal sphincters: manometric evaluation of anorectal continence

To investigate the exact nature of anorectal continence, a manometric evaluation was performed in 88 healthy test persons with a two-balloon catheter. The pressure in the anal canal (PAC) and the rectal ampulla at rest (PAR), the maximum squeeze pressure (PAC max) and pressure rise in the anal canal after dilatation of the rectal ampulla delta PAC) were evaluated separately for men and women, and the test persons were divided into 3 age groups (group I: under 40 years, group II: 40-60 years, group III: over 60 years). PAC showed a statistically significant difference between men and women and a constant decrease with age--statistically significant for men and for women between groups II and III--whereas the statistical significance of the 3 other values had to be restricted to a constant decrease with advance in years. Anorectal continence is characterized by a PAC at rest of over 40 mm Hg, a PAC max reaching at least 80 mm Hg, a pressure gradient between rectal ampulla and anal canal of over 20 mm Hg and a delta PAC of more than 10 mm Hg. These values as well as the differences depending on age and sex should be kept in mind for the evaluation of the continence function.

[Organization of the cavernous structures of the human rectum]

By means of complex histological and injection methods, including roentgenovasography and morphometry, 140 preparations of the human rectum have been studied during the late and middle fetal period, as well as during all periods of the postnatal ontogenesis. On the lateral walls of the columnar zone of the anal canal, places where the internal haemorrhagic nodes occur especially often, peculiar incapsulated and nonincapsulated microglomal cavernous bodies have been revealed. A large vascular peduncle connects them with the superior rectal artery and vein (according to 2-4 and 8-10 o'clock on the clock face) as complexes consisting of 2-3 penicilli and glomeruli. They are connected with the portocaval anastomoses of the initial multicanal anal-columnar sources of the superior and inferior rectal veins. The latter have various obturative mechanisms represented as microvalves, subintimal muscular toruli and arteriol-venular shunts of the obturative glomal and combined type.

The normal development of the anorectum in the pig

The development of the anorectum was studied in forty-four embryos and foetuses of pig varying in length from 9 mm total length to 210 mm crownrump length and in three newborn pigs. The presence of some features during critical stages in the development of the cloaca in the pig such as an epithelial mass protruding into the dorsal cloaca near its intestinal orifice and distinct differences in the type of epithelium in different regions of the cloacal system greatly facilitated the study of the developmental process. Thus it could be established that a change in position of the dorsal cloaca and adjacent structures such as the distal part of the gut and the urorectal septum via the dorsal part of the cloacal plate towards the tailgroove is of major importance for the partition of the cloaca into a separate intestinal and urogenital division. A subsequent disintegration of the dorsal part of the cloacal plate results in two separate openings for both the systems at the same time. Disintegration of the ventral part of the cloacal plate leads only to a further widening of the external opening of the urogenital system. In the cloacal system three distinct zones were discerned, a dorsal and ventral cloacal and a cloacal plate region. From the dorsal cloacal epithelium the whole anorectal segment between the intestinal mucosa and the anal epidermis develops. The epithelium of ventral cloacal origin seems to disappear completely . Cloacal plate epithelium forms the epithelial lining of distal parts of the urogenital system. The penile urethra in the male is formed by a ventralward movement of the urogenital opening by the growing perineum and not by fusion of genital folds.

Development of enkephalin in the rectum and ganglion of Remak of the chick

Radioimmunoassay (RIA) and high performance liquid chromatography were used in combination with immunocytochemistry to study the development of met-enkephalin (Met-enk) in the rectum and the ganglion of Remak of the chicken. Met-enk was detected by RIA in the rectum at 5 days of incubation (d.i.). The concentration increased from 5-9 d.i. and did not change significantly thereafter. In contrast, the concentration of Met-enk in Remak's ganglion increased throughout the developmental period of study. Met-enk immunoreactivity first appeared in cell bodies in Remak's ganglion at 6 d.i. and in a small number of processes in the wall of the rectum. By 9 d.i., Remak's ganglion contained many immunoreactive cell bodies, some of which extended processes into the wall of the rectum in the region of the myenteric plexus. Varicosities were first seen in the rectum at 13 d.i. and increased in number and staining intensity with developmental age. The fact that immunoreactive cell bodies persist in Remak's ganglion throughout the course of development and send processes into the rectum suggests that a major portion of enkephalinergic innervation of the rectum is extrinsic. On the other hand, the presence of Met-enk immunoreactivity in both nerve cell bodies and processes in rectal explants stripped of Remak's ganglion suggests that this peptide is also contained in intrinsic neurons in the chick rectum.

Kinetics of tissue proliferation in colorectal mucosa during post-natal growth

The main developmental event in the colorectal mucosa during post-natal growth is a dramatic increase in the number of crypts of Lieberkühn, resulting from a longitudinal fission of pre-existing crypts. In the present study, the kinetic aspects of this process have been analysed, using extensive gland and cell counts involving the entire colon and rectum of 24 male BD IX rats distributed into four age groups. The number of crypts was found to rise from an average 4652 to 423,800 between birth and adulthood; the corresponding ratios of bifurcating glands were 13.55 and 0.67%, respectively. Crypt production attained its maximum 18 days after birth with an hourly increment of 519 units. The time spent by replicating glands in the bifurcating stage ('fission time') averaged 6.9--10.5 hr. The mean number of epithelial cells per crypt rose from 249 in 4-day old rats to 635 in adults. The estimated total number of epithelial cells in the colon and rectum was one million in newborns and 248 million in adults. The increment in cell number peaked 3 weeks after birth with a value of 310,000/hr. During the first few days after birth, all cells produced in the epithelium were retained. Cell loss thereafter rapidly progressed, reaching 70% of the cell production in 3-week old animals.