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The urethra, or canal by which the urine reaches the surface, leads from the bladder, its aperture lying in the median plane, not far from the openings of the ureters, but on a lower and anterior plane. The size and shape of the bladder, the thickness of its wall, and also to a great extent its relations, vary with the amount of distension, or contraction, of the organ. When the bladder is empty, or only slightly distended, it lies within the pelvis minor; as it becomes filled with urine it rises above the pubis, and crossing the pelvic brim, enters the
FIG. 989.-MEDIAN SECTION THROUGH THE PELVIS OF AN ADULT MALE SUBJECT.
The urinary bladder is empty and firmly contracted. The coils of small intestine have been removed to afford a view of the side wall of the pelvic cavity.
abdominal cavity. These changes affect chiefly the upper part of the bladder, which becomes altered in shape and size, and acquires new connexions and relations; the lower portion varies but slightly with the amount of distension of the organ (see Figs. 989 and 990). The upper part of the bladder is covered with peritoneum, which is reflected on to it from the anterior abdominal wall in front, from the sides of the pelvis laterally, and, in the male, across the seminal vesicles and terminal parts of the ductus deferentes from the rectum behind. In the female the peritoneum passes on to the bladder posteriorly from the anterior surface of the uterus. peritoneum dips down posteriorly for a certain distance between the bladder and
rectum in t
rectum in the male, forming the recto-vesical or recto-genital pouch; in the female a slit-like peritoneal depression, called the utero-vesical pouch, intervenes between the anterior surface of the uterus and the bladder (Fig. 996). The inferior part of the bladder lies below the peritoneum, and is for the most part directed towards the pelvic floor. In the median plane it is supported by the symphysis pubis and the 2 retro-pubic pad of fat; farther back in the male it rests upon the prostate and on the lower part of the rectum, from the latter of which it is separated by the vesiculæ seminales and the terminal parts of the ductus deferentes. In the female it rests
Sphincter urethræ membranaceæ
Bulb of urethra
The urinary bladder and rectum are both greatly distended.
upon the anterior wall of the vagina. Laterally the bladder is supported by the levatores ani muscles, and farther from the median plane it rests on each side on the obturator internus; it is separated from the layer of the pelvic fascia covering these muscles by loose areolar tissue.
The opening of the urethra, orificium urethra internum or internal urethral orifice, is placed in, or near, the part of the bladder wall which lies lowest in the pelvic cavity. The term neck, or cervix, is often applied to this region, the
bladder appearing as if it were suddenly constricted to form the urethra. The portion of the bladder wall posterior to the urethral orifice, which is directed in the male towards the anterior wall of the rectum and lies below and in front of the recto-vesical pouch, is called the fundus vesica or base of the bladder; it is closely related to the seminal vesicles and ampullæ of the ductus deferentes. The corresponding part of the bladder in the female rests against the anterior wall of the vagina. The term vertex vesicæ, or apex of the bladder, is applied to the portion which lies nearest to the upper border of the symphysis when the organ is empty, and rises high above the pubis into the abdominal cavity when the bladder is distended. Connected with the vertex of the bladder is a fibrous cord, the ligamentum umbilicale medium, or urachus, which passes upwards, in the Area continuous median plane, on the posterior aspect
Apex of bladder
of the anterior abdominal wall, and reaches the umbilicus. It represents the passage which in the embryo connects the developing bladder with the allantois. The part of the bladder connecting the apex with the base, and
FIG. 991.-INFERIOR ASPECT OF THE
viscera had been hardened in situ.
URINARY BLADDER. From a subject in which the not sharply marked off from either, is called the corpus vesica, or body of the bladder.
Position of the Urethral Orifice. -During the various changes in shape
and size which the bladder undergoes, the region of the internal urethral orifice remains almost fixed in position. The urethral orifice lies immediately above the prostate, and behind and slightly below the level of the upper margin of the symphysis pubis, from which it is distant about two to two and a half inches. It can be easily reached by a finger introduced into the bladder through the abdominal wall above the symphysis pubis. It is usually placed half an inch to one inch above the level of a plane passing through the lower margin of the symphysis and the lower end of the sacrum, but in some cases it is found to be somewhat lower. In the female it normally occupies a lower level than in the male. The comparatively slight variations in the level of the internal urethral orifice which do occur, depend partly upon the quantity of fluid contained in the bladder, and partly upon the amount of distension of the lower portion of the rectum. When the bladder is very much distended this region lies at a slightly lower level in the pelvis than it does when the organ is empty; on the other hand, distension of the lower part of the rectum raises, to some extent, the level of the urethral orifice. Since the position of the internal urethral orifice varies, in the manner just described-with the condition of the rectum and of the bladder-it follows that it lies at its lowest limit when the bladder is full and the rectum empty, and at its highest level when the bladder is empty and the rectum distended.
Seminal vesicle FIG. 992. THE URINARY BLADDER, PROSTATE, AND SEMINAL VESICLES, VIEWED FROM BELOW. Taken from a subject in which the viscera were hardene-i in situ. Same specimen as Fig. 993, A. The bladder contained but a small amount of fluid.
Inferior Aspect of the Bladder.-The lower part of the bladder, which is directed towards the pelvic floor, changes, as we have seen, but slightly with the varying amount of distension of the viscus. When the organ has been carefully hardened
before its removal from the body, it is possible to map out on its inferior aspect three convex triangular areas, which may be distinguished from one another by the directions in which they look. The three areas approach one another in the region of the urethral orifice, where, in the male, a portion of the inferior aspect of the bladder wall is structurally continuous with the upper part of the prostate. Posterior to the urethral orifice is a triangular district, directed downwards and backwards, and related, in the male, to the seminal vesicles and the terminal portions of the ductus deferentes, which, together with the recto-vesical layer of the pelvic fascia, intervene in this position between the bladder and the rectum. This triangular area is known as the fundus, base, or postero-inferior surface of the bladder, and in the female it is directed against the anterior wall of the vagina. The rest of the inferior aspect of the bladder is formed by two infero-lateral areas, or surfaces, which meet in the median plane in front of the urethral orifice, and are directed for the most part downwards and laterally (see Fig. 993). Each of these areas extends backwards to join the fundus or postero-inferior surface, along a rounded border which lies between the point where the ureter reaches the bladder and the urethral orifice. The infero-lateral part of the bladder wall rests on the areolar tissue covering the fascia of the levator ani and the obturator internus muscles, and, nearer the median plane, upon the os pubis and the retro-pubic pad of fat.
Lig. um- Seminal
Median umbilical ligament (urachus)
FIG. 993. THE URINARY BLADDER, PROSTATE, AND VESICULA SEMINALIS, VIEWED FROM THE LATERAL ASPECT. Drawn from specimens in which the viscera were hardened before removal from the body. In A the bladder contained but a very small quantity of fluid; in B the quantity was somewhat greater. In A the peritoneum is shown covering the superior surface of the bladder, and its cut edge is seen where it is reflected along the lateral border of the organ. In B the level of the peritoneal reflexion is indicated by a dotted line.
The three rounded borders which mark off the three triangular areas on the inferior aspect of the bladder, just described, extend from the region of the urethral orifice to the bladder apex, and to the points where the ureters reach the bladder wall (see Figs. 991, 992).
Shape and Relations of the Empty Bladder.-When the bladder is empty, or nearly so, it has, roughly speaking, the shape of an inverted tetrahedron, whose apex corresponds to the point where the urethra leaves the organ, while the base of the tetrahedron is formed by the superior surface of the bladder. The three basal angles of the tetrahedron correspond to the bladder apex and to the two posterior angles of the bladder, or points where the ureters join the organ. The three surfaces, which meet inferiorly at the urethral orifice, are only marked off from one another by rounded borders, but as long as the organ is empty, or nearly so, they are separated by distinct borders from the superior surface. These three areas have been already described as the infero-lateral surfaces and the base of the bladder (Figs. 991 and 992). Their relations have also been indicated. The superior surface of the empty bladder looks upwards into the pelvic cavity; it is convex when the organ is contracted, concave when relaxed. This surface is covered with peritoneum, and its outline, which is approximately triangular, is determined by lateral and posterior borders (Fig. 993). The lateral borders of the empty bladder are sharply marked, and extend from the bladder apex to the posterior angles
of the bladder, or points where the ureters join the organ. They separate the superior surface from the infero-lateral portions of the inferior aspect of the bladder wall (Fig. 993, A). The posterior border stretches across between the posterior angles of the bladder, and separates the superior from the basal surface of the viscus. The superior surface is related in the male to coils of intestine; in the female it is related also to the anterior surface of the uterus. The lateral border of the empty bladder lies against the pelvic fascia just above, or at the level of, the arcus tendineus of the levator ani muscle. The ductus deferens crosses the side wall of the pelvis parallel to it, but at a considerably higher level. In median section the cavity of the empty and relaxed bladder often presents the appearance of a Y-shaped chink, the stem of the Y being represented by the urethra as it leaves the organ, and the two limbs by the narrow intervals between the superior surface and the under parts of the bladder wall which lie in front of and behind the urethral orifice. This relaxed form is sometimes described as the diastolic condition of the empty bladder, and is found associated with a bladder wall of but little thickness, and with a concave upper surface. The condition is usually the result of an escape of fluid after death, when the bladder wall has lost the power of contracting. It does not represent
Ilio-pectineal eminence Inferior epigastric artery
FIG. 994.-VIEW LOOKING INTO THE PELVIS FROM ABOVE AND SOMEWHAT BEHIND.
a normal condition of the organ in the living. The normal empty bladder is strongly contracted, and its wall is thick and firm. A distinctly Y-shaped appearance is not presented by its cavity in median section, but the interior of the organ is seen as a simple narrow interval continuous with the canal of the urethra.
Distended Bladder.-As the bladder fills with fluid the superior wall is raised upwards from the infero-lateral and basal walls, and, at the same time, the borders separating the superior from the other surfaces of the bladder become at first more rounded and then nearly obliterated. The lateral borders of the bladder becoming in this manner opened out, give rise to so-called lateral surfaces in the distended organ. These surfaces, however, are not sharply marked off, and are directly continuous with the superior surface. During distension, also, the angles present in the empty condition of the organ become rounded as the entire bladder wall becomes more uniformly convex. The general shape of the bladder becomes altered during distension; the tetrahedral form of the empty organ is lost, and the bladder as it becomes filled assumes first a somewhat spherical, then an oval contour. During distension the enlarging bladder comes to occupy more and more of the pelvic cavity, displacing upwards the portions of the colon and small intestine which may lie in the pelvis when the organ is empty. Until all the available pelvic space has been filled up, the form