Talk:Urinary Bladder Development

2010

Endodermal origin of bladder trigone inferred from mesenchymal-epithelial interaction

J Urol. 2010 Jan;183(1):386-91.

Tanaka ST, Ishii K, Demarco RT, Pope JC 4th, Brock JW 3rd, Hayward SW.

Department of Urologic Surgery, Monroe Carell, Jr Children's Hospital at Vanderbilt, Nashville, Tennessee 37232-9820, USA. stacy.tanaka@vanderbilt.edu

Abstract PURPOSE: In the classic view of bladder development the trigone originates from the mesoderm derived wolffian ducts while the remainder of the bladder originates from the endoderm derived urogenital sinus. Recent molecular developmental studies have questioned the veracity of this received wisdom, suggesting an endodermal origin for the trigone. To shed further light on this issue we observed mesenchymal-epithelial interactions between trigone epithelium and fetal urogenital sinus mesenchyma to infer the trigonal germ layer of origin.

MATERIALS AND METHODS: Mouse trigone epithelium was recombined with fetal rat urogenital sinus mesenchyma in tissue recombinant grafts that were placed beneath the renal capsule of athymic mouse hosts. Grafts were harvested at 4 weeks. Control grafts with bladder dome and ureteral epithelium were also examined. Tissues were evaluated with hematoxylin and eosin, and Hoechst dye 33258 to confirm cell species origin. Immunohistochemistry was done with androgen receptor, broad spectrum uroplakin, dorsolateral prostate secretions and seminal vesicle secretions to differentiate prostatic and seminal vesicle differentiation.

RESULTS: Grafts of mouse trigone epithelium with fetal rat urogenital sinus mesenchyma yielded epithelial tissue that stained for dorsolateral prostate secretions but not for seminal vesicle secretions. Control grafts of bladder dome epithelium yielded the expected endodermal prostate differentiation. Control grafts of ureteral epithelium yielded the expected mesodermal seminal vesicle differentiation.

CONCLUSIONS: The consistent finding of prostatic epithelium in tissue recombinants of trigone epithelium and fetal urogenital sinus mesenchyma reinforces the hypothesis that the trigone is derived from the endoderm and not from the mesoderm, as commonly accepted.

PMID: 19914648 http://www.ncbi.nlm.nih.gov/pubmed/19914648

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2794964

http://www.jurology.com/article/S0022-5347(09)02320-9/abstract

Gray's Anatomy - The Urinary Bladder

(Vesica Urinaria; Bladder)

The urinary bladder (Fig. 1135) is a musculomembranous sac which acts as a reservoir for the urine; and as its size, position, and relations vary according to the amount of fluid it contains, it is necessary to study it as it appears (a) when empty, and (b) when distended.) In both conditions the position of the bladder varies with the condition of the rectum, being pushed upward and forward when the rectum is distended.

The Empty Bladder

When hardened in situ, the empty bladder has the form of a flattened tetrahedron, with its vertex tilted forward. It presents a fundus, a vertex, a superior and an inferior surface. The fundus (Fig. 1152) is triangular in shape, and is directed downward and backward toward the rectum, from which it is separated by the rectovesical fascia, the vesiculæ seminales, and the terminal portions of the ductus deferentes. The vertex is directed forward toward the upper part of the symphysis pubis, and from it the middle umbilical ligament is continued upward on the back of the anterior abdominal wall to the umbilicus. The peritoneum is carried by it from the vertex of the bladder on to the abdominal wall to form the middle umbilical fold. The superior surface is triangular, bounded on either side by a lateral border which separates it from the inferior surface, and behind by a posterior border, represented by a line joining the two ureters, which intervenes between it and the fundus. The lateral borders extend from the ureters to the vertex, and from them the peritoneum is carried to the walls of the pelvis. On either side of the bladder the peritoneum shows a depression, named the paravesical fossa (Fig. 1037). The superior surface is directed upward, is covered by peritoneum, and is in relation with the sigmoid colon and some of the coils of the small intestine. When the bladder is empty and firmly contracted, this surface is convex and the lateral and posterior borders are rounded; whereas if the bladder be relaxed it is concave, and the interior of the viscus, as seen in a median sagittal section, presents the appearance of a V-shaped slit with a shorter posterior and a longer anterior limb—the apex of the V corresponding with the internal orifice of the urethra. The inferior surface is directed downward and is uncovered by peritoneum. It may be divided into a posterior or prostatic area and two infero-lateral surfaces. The prostatic area is somewhat triangular: it rests upon and is in direct continuity with the base of the prostate; and from it the urethra emerges. The infero-lateral portions of the inferior surface are directed downward and lateralward: in front, they are separated from the symphysis pubis by a mass of fatty tissue which is named the retropubic pad; behind, they are in contact with the fascia which covers the Levatores ani and Obturatores interni.

FIG. 1135– Median sagitta section of male pelvis. (See enlarged image)

When the bladder is empty it is placed entirely within the pelvis, below the level of the obliterated hypogastric arteries, and below the level of those portions of the ductus deferentes which are in contact with the lateral wall of the pelvis; after they cross the ureters the ductus deferentes come into contact with the fundus of the bladder. As the viscus fills, its fundus, being more or less fixed, is only slightly depressed; while its superior surface gradually rises into the abdominal cavity, carrying with it its peritoneal covering, and at the same time rounding off the posterior and lateral borders.

The Distended Bladder.—When the bladder is moderately full it contains about 0.5 liter and assumes an oval form; the long diameter of the oval measures about 12 cm. and is directed upward and forward. In this condition it presents a postero-superior, an antero-inferior, and two lateral surfaces, a fundus and a summit. The postero-superior surface is directed upward and backward, and is covered by peritoneum: behind, it is separated from the rectum by the rectovesical excavation, while its anterior part is in contact with the coils of the small intestine. The antero-inferior surface is devoid of peritoneum, and rests, below, against the pubic bones, above which it is in contact with the back of the anterior abdominal wall. The lower parts of the lateral surfaces are destitute of peritoneum, and are in contact with the lateral walls of the pelvis. The line of peritoneal reflection from the lateral surface is raised to the level of the obliterated hypogastric artery. The fundus undergoes little alteration in position, being only slightly lowered. It exhibits, however, a narrow triangular area, which is separated from the rectum merely by the rectovesical fascia. This area is bounded below by the prostate, above by the rectovesical fold of peritoneum, and laterally by the ductus deferentes. The ductus deferentes frequently come in contact with each other above the prostate, and under such circumstances the lower part of the triangular area is obliterated. The line of reflection of the peritoneum from the rectum to the bladder appears to undergo little or no change when the latter is distended; it is situated about 10 cm. from the anus. The summit is directed upward and forward above the point of attachment of the middle umbilical ligament, and hence the peritoneum which follows the ligament, forms a pouch of varying depth between the summit of the bladder, and the anterior abdominal wall. 4

FIG. 1136– Male pelvic organs seen from right side. Bladder and rectum distended; relations of peritoneum to the bladder and rectum shown in blue. The arrow points to the rectovesical pouch. (See enlarged image)

The Bladder in the Child

(Figs. 1137, 1138).—In the newborn child the internal urethral orifice is at the level of the upper border of the symphysis pubis; the bladder therefore lies relatively at a much higher level in the infant than in the adult. Its anterior surface “is in contact with about the lower two-thirds of that part of the abdominal wall which lies between the symphysis pubis and the umbilicus” (Symington 177). Its fundus is clothed with peritoneum as far as the level of the internal orifice of the urethra. Although the bladder of the infant is usually described as an abdominal organ, Symington has pointed out that only about one-half of it lies above the plane of the superior aperture of the pelvis. Disse maintains that the internal urethral orifice sinks rapidly during the first years, and then more slowly until the ninth year, after which it remains sta when it again slowly descends and reaches its adult position.

FIG. 1137– Sagittal section through the pelvis of a newly born male child. (See enlarged image)

FIG. 1138– Sagittal section through the pelvis of a newly born female child. (See enlarged image)

The Female Bladder (Fig. 1139).—In the female, the bladder is in relation behind with the uterus and the upper part of the vagina. It is separated from the anterior surface of the body of the uterus by the vesicouterine excavation, but below the level of this excavation it is connected to the front of the cervix uteri and the upper part of the anterior wall of the vagina by areolar tissue. When the bladder is empty the uterus rests upon its superior surface. The female bladder is said by some to be more capacious than that of the male, but probably the opposite is the case.

FIG. 1139– Median sagittal section of female pelvis. (See enlarged image)

Ligaments

The bladder is connected to the pelvic wall by the fascia endopelvina. In front this fascial attachment is strengthened by a few muscular fibers, the Pubovesicales, which extend from the back of the pubic bones to the front of the bladder; behind, other muscular fibers run from the fundus of the bladder to the sides of the rectum, in the sacrogenital folds, and constitute the Rectovesicales.

The vertex of the bladder is joined to the umbilicus by the remains of the urachus which forms the middle umbilical ligament, a fibromuscular cord, broad at its attachment to the bladder but narrowing as it ascends.

From the superior surface of the bladder the peritoneum is carried off in a series of folds which are sometimes termed the false ligaments of the bladder. Anteriorly there are three folds: the middle umbilical fold on the middle umbilical ligament, and two lateral umbilical folds on the obliterated hypogastric arteries. The reflections of the peritoneum on to the side walls of the pelvis form the lateral false ligaments, while the sacrogenital folds constitute posterior false ligaments.

Interior of the Bladder (Fig. 1140).—The mucous membrane lining the bladder is, over the greater part of the viscus, loosely attached to the muscular coat, and appears wrinkled or folded when the bladder is contracted: in the distended condition of the bladder the folds are effaced. Over a small triangular area, termed the trigonum vesicæ, immediately above and behind the internal orifice of the urethra, the mucous membrane is firmly bound to the muscular coat, and is always smooth. The anterior angle of the trigonum vesicæ is formed by the internal orifice of the urethra: its postero-lateral angles by the orifices of the ureters. Stretching behind the latter openings is a slightly curved ridge, the torus uretericus, forming the base of the trigone and produced by an underlying bundle of non-striped muscular fibers. The lateral parts of this ridge extend beyond the openings of the ureters, and are named the plicæ uretericæ; they are produced by the terminal portions of the ureters as they traverse obliquely the bladder wall. When the bladder is illuminated the torus uretericus appears as a pale band and forms an important guide during the operation of introducing a catheter into the ureter.