The bladder is a hollow muscular organ that serves as a reservoir for urine. In women, its posterior wall and dome are invaginated by the uterus. The adult bladder normally has a capacity of 400–500 mL.
When empty, the adult bladder lies behind the pubic symphysis and is largely a pelvic organ. In infants and children, it is situated higher (Berrocal et al, 2002). When it is full, it rises well above the symphysis and can readily be palpated or percussed. When overdistended, as in acute or chronic urinary retention, it may cause the lower abdomen to bulge visibly.
Extending from the dome of the bladder to the umbilicus is a fibrous cord, the median umbilical ligament, which represents the obliterated urachus. The ureters enter the bladder posteroinferiorly in an oblique manner and at these points are about 5 cm apart (Figure 1–6). The orifices, situated at the extremities of the crescent-shaped interureteric ridge that forms the proximal border of the trigone, are about 2.5 cm apart. The trigone occupies the area between the ridge and the bladder neck.
The internal sphincter, or bladder neck, is not a true circular sphincter but a thickening formed by interlaced and converging muscle fibers of the detrusor as they pass distally to become the smooth musculature of the urethra.
In males, the bladder is related posteriorly to the seminal vesicles, vasa deferentia, ureters, and rectum (Figures 1–7 and 1–8). In females, the uterus and vagina are interposed between the bladder and rectum (Figure 1–9). The dome and posterior surfaces are covered by peritoneum; hence, in this area, the bladder is closely related to the small intestine and sigmoid colon. In both males and females, the bladder is related to the posterior surface of the pubic symphysis, and, when distended, it is in contact with the lower abdominal wall.
A: Anatomic relationship of the bladder, prostate, prostatomembranous urethra, and root of the penis. B: Histology of the testis. Seminiferous tubules lined by supporting basement membrane for the Sertoli and spermatogenic cells. The latter are in various stages of development. C: Cross sections of the testis and epididymis. (A and C are reproduced, with permission, from Tanagho EA: Anatomy of the lower urinary tract. In: Walsh PC et al [eds] Campbell's Urology, 6th edn., Vol. 1. Saunders, Philadelphia, PA, 1992.)
Top: Relations of the bladder, prostate, seminal vesicles, penis, urethra, and scrotal contents. Lower left: Transverse section through the penis. The paired upper structures are the corpora cavernosa. The single lower body surrounding the urethra is the corpus spongiosum. Lower right: Fascial planes of the lower genitourinary tract. (After Wesson.) (Tanagho EA: Anatomy of the lower urinary tract. In: Walch PC et al [eds] Campbell's Urology. 6th edn., Vol. 1. Saunders, Philadelphia, PA, 1992.)
Anatomy and relations of the bladder, urethra, uterus and ovary, vagina, and rectum.
The mucosa of the bladder is composed of transitional epithelium. Beneath it is a well-developed submucosal layer formed largely of connective and elastic tissues. External to the submucosa is the detrusor muscle that is made up of a mixture of smooth muscle fibers arranged at random in a longitudinal, circular, and spiral manner without any layer formation or specific orientation except close to the internal meatus, where the detrusor muscle assumes three definite layers: inner longitudinal, middle circular, and outer longitudinal (John et al, 2001).
Left: Histology of the prostate. Epithelial glands embedded in a mixture of connective and elastic tissue and smooth muscle. Right: Histology of the bladder. The mucosa is transitional cell in type and lies on a well-developed submucosal layer of connective tissue. The detrusor muscle is composed of interlacing longitudinal, circular, and spiral smooth-muscle bundles.
The bladder is supplied by the superior, middle, and inferior vesical arteries, which arise from the anterior trunk of the internal iliac (hypogastric) artery, and by smaller branches from the obturator and inferior gluteal arteries. In females, the uterine and vaginal arteries also send branches to the bladder.
Surrounding the bladder is a rich plexus of veins that ultimately empties into the internal iliac (hypogastric) veins.
The bladder receives innervation from sympathetic and parasympathetic nervous systems. The sensory afferent of the bladder originates from both subepithelial nerve endings and nerve fibers between detrusor muscle bundles (Andersson, 2010; Birder et al, 2010; McCloskey, 2010).
The lymphatics of the bladder drain into the vesical, external iliac, internal iliac (hypogastric), and common iliac lymph nodes.