Bladder

The urinary bladder is a hollow muscular organ, which serves as a reservoir for the storage and voluntary expulsion of urine. When filled to capacity, the bladder is spherical and holds approximately 500 mL of fluid; however, this capacity can vary based on one's size, sex, or age. The bladder lies in the anterior half of the pelvis and it is bounded anteriorly by the symphysis pubis, laterally by the pelvic sidewalls, and posteriorly by the vagina, cervix, and uterus. The urachus terminates in the umbilicus and anchors the apex of the bladder to the anterior abdominal wall via the median umbilical ligament. Fascia intimately surrounds the bladder surface. The peritoneal lining and cavity cover the superior surface. The transversalis fascia covers the anterolateral surface and the posterior surface is covered by endopelvic fascia.

As described by DeLancey,3 the bladder, uterus, vagina, and rectum are attached to the lateral pelvic walls by a network of connective tissue, which is collectively called the endopelvic fascia. This fascia is a continuous unit that is divided into sections that have named parts. The fascia, which attaches the uterus to the lateral pelvis is called the parametria and consists of the broad, cardinal, and uterosacral ligaments. The fasciae that attach the vagina to the pelvis are collectively called the paracolpium. These fasciae contain smooth muscle, blood vessels, lymphatics, and nerves. The paracolpium, cardinal, and uterosacral ligaments are displayed in Figure 4-1.3. The endopelvic fascial support of the vagina is divided into three levels: I, II, and III [Figure 4-1.4; please see Figure 4-2.7, Chapter 4-2 (Genital Anatomic Correlates)]. The most cephalic 3 cm of the vagina is suspended by endopelvic fascia, which extends from the vagina posteriorly and superiorly over the piriformis muscle to the lateral portion of the sacrum. This constitutes level I support, and alteration of this fascia will result in vaginal apex and uterine prolapse. The mid portion of the anterior vagina is attached laterally to the arcus tendineus fasciae of the pelvic sidewall. This layer lies below the bladder body, and contributes support to the bladder and vagina within the pelvis. This portion of the endopelvic fascia is known as the pubocervical fascia. Tears or disruption of the pubocervical fascia via various mechanisms will result in a cystocele. An injury to the central portion of this fascia results in a central cystocele defect. An injury to this fascia between the vagina and the

Rectum

Rectum

Figure 4-1.3. The bladder, uterus, vagina,and rectum are attached to the lateral pelvic walls by a network of connective tissue,which is collectively called the endopelvic fascia. This fascia is a continuous unit that is divided into sections that have named parts.

(Reprinted with the permission of The Cleveland Clinic Foundation.)

Figure 4-1.3. The bladder, uterus, vagina,and rectum are attached to the lateral pelvic walls by a network of connective tissue,which is collectively called the endopelvic fascia. This fascia is a continuous unit that is divided into sections that have named parts.

(Reprinted with the permission of The Cleveland Clinic Foundation.)

tendineus arc will result in a paravaginal cystocele defect. The posterior wall of the vagina is attached to the superior fascia of the levator ani muscles and forms the rectovagi-nal fascia. Injury to this portion of the endopelvic fascia will result in a rectocele. The anterior and posterior endopelvic fascia of the mid vaginal wall constitutes level II support. The region of the vagina that extends 2 to 3 cm above the hymenal ring is fused to the urethra, medial surface of the levator ani muscles, and the perineal body. At this level,there is no intervening connective tissue of the endopelvic fascia that separates the vagina from the urethra. This portion of the vagina and endopelvic fascia constitutes level III support. The levator muscles provide additional support to pelvic organs by closing the vagina and forming a shelf, which supports these organs. Strain on the pelvic organ fascial supports through gravity and Valsalva, are limited by the levator ani muscle. Alteration to the integrity or function of the pelvic floor muscle and fascial supports results in pelvic organ prolapse.

On a microscopic basis, the bladder wall comprises an inner transitional cell lining, a middle muscular layer, and an outer adventitial layer. The inner transitional cell lining is covered by a glycosaminoglycan layer, which is thought to be a protective barrier from urinary irritants. The transitional cell epithelium comprises six layers of cells that rest on a basement membrane. Deep to the basement membrane is a thick fibroelastic connective tissue called the lamina propria. The lamina propria contains many blood vessels and loosely arranged smooth muscle fibers. The middle muscular layer consists of three large interlacing bundles of smooth muscle: an inner longitudinal, middle circular, and an outer longitudinal muscular layer. The outer adventitial layer consists of fat and connective tissue.

The gross evaluation of the bladder interior is done by cystoscopy, which is a common clinical tool for evaluation of intravesical pathology. On placement of the cystoscope into the urethra,the urethral mucosa is compressed and the urethra is closed. The cystoscope can be easily placed through the closed urethra. The trigone, which has been previously described, is the first structure seen on placement of the cystoscope into the bladder. The trigone is triangular in shape as a result of the internal urethral opening being equidistant to the ureteral orifices, forming an equilateral triangle. It is common to observe a fluffy white coating on the trigone surface of women, which is known as squamous metaplasia. The ureteral orifices lie approximately 3 cm apart and usually appear as small slits; however, there can be many variations to their appearance. The ureteral bars and the interureteric ridge are often used to locate the ureteral orifices; therefore, knowing the relationship of these structures is critical. The mucosa of the bladder is wrinkled or folded when the bladder is empty, and smooth when the bladder is full. This occurs because the mucosa is loosely bound to the underlying musculature on most of the detrusor surface, except for the trigone, which always appears smooth. On the surface of the bladder mucosa are numerous superficial blood vessels. An

Figure 4-1.4. The three levels of pelvic support of the vagina and uterus showing the continuity of supportive structure throughout the entire length of the genital tract. (Reprinted with the permission of The Cleveland Clinic Foundation.)

Figure 4-1.4. The three levels of pelvic support of the vagina and uterus showing the continuity of supportive structure throughout the entire length of the genital tract. (Reprinted with the permission of The Cleveland Clinic Foundation.)

air bubble is often introduced during cystoscopy and can be seen in the dome of the bladder. This bubble is used to identify the dome and allows for orientation during cystoscopy. The impression of the uterus on the anterior surface of the bladder can be appreciated in its partially filled state.

The arterial supply of the bladder arises from the superior and inferior vesical arteries, which are branches of the internal iliac vessels. The superior vesicular artery is usually a single artery, but may have 2 to 3 branches that supply the dome and posterior portions of the bladder. The venous drainage of the bladder originates from the dorsal vein of the clitoris as it bifurcates to empty into the laterally placed vaginal plexuses. This plexus of veins connects with the ovarian, uterine, and rectal plexuses to drain into the internal iliac veins.

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