Since the form of the urinary bladder varies greatly according to the volume of its content, it is not easy to ascertain its morphology except the area near its base. This accounts for the scarcity of its adequate description. Recenty, however, the results of cystography and of cystoscopy are directly utilized in making diagnosis and in determining operative indications.
The present study pertains to the development of urological organs of Japanese fetuses, forming a part of the several subject, and attempts to investigate the morphology of the urinary bladder as basic knowledge.
The materials used for this study were selected from over 500 fetal cadavers ranging in gestation age from 4th to 10th months, and observations were made on the cystograms taken within the reasonably satisfactory limits of accuracy.
For this purpose some new measurement lines serving as morphologic landmarks were constructed.
1) The development of the urinary bladder has been described by such authors as Campbell, Hurbet, Tsusaki, Takashima, Nagamine and others. The cloaca undergoes differentiation during the 6th fetal month into the rectal cloaca posteriorly and the urachus anteriorly, the latter in the female forms the entire urethra, while in the male the inferior aspects forms the posterior urethra. The urinary bladder develops from a portion of the cloaca.
The bladder, therefore, develops from the cranial aspect of the ventral cloacal remnant, and, being a long spindle in shape at first, turns into a pear-shaped organ during the terminal stage of embryonic life.
2) The development of the pelvis was a necessary accompaniment of the differentiation of the urinary bladder, and careful observations were also made on this problem. The distance between the right and left spines of the ilium, which is 2.3cm at the 4th fetal months, decrease to 6.62cm during the 10th month, or about 3 times. The body length of 0.82cm in the 4th month also increases to 2.48cm, or about 3 times, during the 10th month. The growth of the total longitudinal diameter of the entire pelvis is 1.47cm during the 4th month but becomes 4.65cm during the 10th month, or an increase of about 3.5 times.
3) The bladder volume is 0.22cc during the 4th month but increases to 1.9cc during the 5th, to 3.43cc during the 9th and to 7.0cc during the 10th month.
4) The increase of cystogram is represented by that of the maximum longitudinal diameter of 0.48cm during the 4th month month and 3.17 during the 10th month.
The maximum lateral diameter is 0.706 during the 4th month and 2.72cm during the 10th month. There are two periods of rapid growth during this period, namely, 5-6th month and 9-10th month.
5) The area of cystogram increases from 47mm
2 during the 4th month to 665mm
2 during the 10th month. Likewise, during this period there seem to be two perieds of rapid growth, namely, 4-5-6th fetal month and 9-10th month.
6) The regard to the position of cystogram, the pelvis and the bladder grow upward during the two periods, namely, between 4-6th fetal months and 9-10th months. After the pelvis is formed, the bladder seems to descend to be situated directly above the pubic bones and to change to the adult position. The enlargement of the bladder in its transverse (left and right) diameter appears to involve predominantly the right side, but become almost equilateral during the 7th month, only to show again a greater development on the right side during the 10th month.
7) The shape of cystogram can be classified into 4 kinds with 14 types. Many are spherical during the 4-5th months, but oval or elliptical shape predominate during the 6-7th months. In the terminal stage of gestation, it becomes spherical again to be transformed into the adult type.
8) The shape of the bladder neck has beeh classified into 7 kinds with 14 types. During the first half of gestation the bladder neck are mostly wide, the so-called relaxed
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