日本人胎児の直腸に開口する小管の研究

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The urethra is provided with a complex structure known as praurethal ducts which play an extremely important role in infammatory diseases. These structure exist not only in the :internal urethra, but also in the labiomarginal portion, external orifice, dorsal and ventral aspects of prepuce and penis, extending to the perineum. Occasionally, the passage may reach the perirectal area from the perineum. The urethra and recto-anal area are not only the neighboring organs to each other, but they also may be considered to have a common origin ,during the period of betal development, since both of these organs differentiate from the common cloaca, with this fact in mind, the authors has undertaken an investigation in order to determine whether or not a mucous duct with a structure similar to the paraurethral passage in the lower rectum as in the urethra. Fetal materials have been utilized for the study, a total of 30 fetuses ranging in age from 5 to 9 months of gestation,which facilitated the manipulation of the tissue, the incision was made from the lower anterior wall of the abdomen extending to the perineum and a circular piece was cut about 3-4 cm around the anus and a block of tissue about 4-5 cm upward obliquely was removed: After fixation the paraffin-embeded tissue was prepared in serial sections. The observation was made by measuring the thickness of these sections in units of microns (μ), the calculation being made from the portion appearing in circles around the anal ring. The existence of ductules was demonstrated beneath the mucous membrane of the rectum, the number of the ducts ranging from 1-2 up to many scroes on the cut surface of the section ,and presenting a rather complicated appearance. Having stratified efithelium as their lining apithelium, these ducts were generally small ductules with no glandular structure. The principal structural features of these ductules may be summarized as follows: 1. The pararectal ducts opens into the wall of the rectum. The opening is usually at the upper side in most cases with the duct cavity usually directed downward, although exceptionally it is in a reverse direction, so that some have openings at the lower side with cavities in the upper side, while others open at the middle portion of the duct with cavities at both upper and lower sides. 2. The morphology of pararectal ductules is extremely variable but they can generally be distinguished into 3 types. (a) simple, (b) ramified, and (c) branched into a complicated pattern. Many of the ductules show a tendency to be aggregated at some portion, although there are others with irregular distribution. When viewed on their cross sections, they may be few in number (1-2), or moderately numerous (over 20), or still they may be closely packed. An attempt was made in the present investigation to observe the duct cavities in entire series of section by copying them in model diagrams, which enabled the author to study the details of simple and ramified ductules as wells as those with complicated ramifications and the manner of their distribution. 3. The lining epithelium of the pararectal ductule is composed generally of strutified epithelium which is present in the neighborhood of the rectum in many locations, and there may be a coexitence of cylindrical cells and transparent cells. However, there is no association with any glandular structure. The terminal portion of the ductules forms a blind sac as a rule. 4. The size of the ductules varies since it largely depends. on the manner of small cavity formation. There are some relatively large ductules forming ramifications by the conjugation of mucous folds, but others form small cavities by constriction and ramification on their descending way, as to the number of these ductules varies from the main passage above mentioned to those showing ramification and re-ramification presenting a complex structure as well as those forming an aggregation. There is evidently difference as to the height of the ductules, so that some persist while others disappear, making it difficult to set standards for measurement. The averge number, however, ranges from 1 to 20. 5. The directional pattern of the ductules is generally downward, usually oblique paths antero-posteriorly or from right to left. The ductules ramifying once or more occupy a fixed area. On the cross sections, they are chiefly located in the connective tissue around the lower rectum, but not infrequently they may be found in the inner circular muscle bundle or even in the longitudinal muscles. 6. Upon comparing the paraurethral with pararectal ductules, the latter is an independent structure, differing from the hitherto described rectal duct and gland not only in location but also in the absence of accompanying glands. On the other hand, the so-called paraurethral ductules may be large, small, simple, complex, regular or irregular. If the question of glandular structure is disregarded from the paraurethral ductule, there is a close resemblance between the two, Considering the general rule that the ductule epithelium roughly coincides with the mucosal structure of the orifice, the paraurethral ductule is provided with glandular structure while the pararectal ductule is not. Naturally, therefore, the paraurethral ductules are comparable to the pararectal ductules, the difference being only in the presence of accompanying glands in the former and its absence in the latter. 7. As to the development of the pararectal ductules, the author's investigation is still not. entirely completed. If the development of the paraurethral ductule may be cited in analogy, one theory favors the origin from the formation of epithelial budding in the fatal period, while the other derives it at the mutual conjugation of the edges of mucosal furrow. According to the findings obtained from the preparations here used, there are instances of new formation by the conjugation of mucosal folds, as well as of independent of small cavity formation resulting from the emergence of a space in the bridged mucosa. This problem will be pursued further in the author's future studies.
社団法人日本泌尿器科学会の論文

日本人胎児の直腸に開口する小管の研究

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