URINARY BLADDER

Hospital Corpsman Revised Edition - Complete Navy Nursing manual for hospital training purposes
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The average amount of urine an adult excretes varies from 1,000 to 1,500 ml per day. However, the amount of urine excreted varies greatly with temperature, water intake, and state of health. No matter how much water one drinks, the blood will always remain at a constant concentration, and the excess water will be excreted by the kidneys. A large water intake does not put a strain on the kidneys. Instead it eases the load of concentration placed on the kidneys. URETERS The ureters' only function is to carry urine from each kidney to the urinary bladder. The ureters are two membranous tubes 1 mm to 1 cm in diameter and about 25 cm in length. Urine is transported through the ureters by peristaltic waves (produced by the ureter's muscular walls). URINARY BLADDER The urinary bladder functions as a temporary reservoir for urine. The bladder possesses features that enable urine to enter, be stored, and later be released for evacuation from the body. Structure The bladder is a hollow, expandable, muscular organ located in the pelvic girdle (fig. 1-59). Although the shape of the bladder is spherical, its shape is altered by the pressures of surrounding organs. When it is empty, the inner walls of the bladder form folds. But as the bladder fills with urine, the walls become smoother. The internal floor of the bladder includes a triangular area called the trigone (fig. 1-59). The trigone has three openings at each of its angles. The ureters are attached to the two posterior openings. The anterior opening, at the apex of the trigone, contains a funnel-like continuation called the neck of the bladder. The neck leads to the urethra. The wall of the bladder consists of four bundles of smooth muscle fibers. These muscle fibers, interlaced, form the detrusor muscle (which surrounds the bladder neck) and comprise what is called the internal urethral sphincter. The internal urethral sphincter prevents urine from escaping the bladder until the pressure inside the bladder reaches a certain level. Parasympathetic nerve fibers in the detrusor muscle function in the micturition (urination) process. The 1-56 HM3F0159 B URETER URETER URINARY BLADDER URINARY BLADDER DETRUSOR MUSCLE (INTERNAL URETHRAL SPHINCTER) PROSTATE GLAND BULBOURETHRAL GLAND PENIS EXTERNAL URETHRAL ORIFICE EXTERNAL URETHRAL ORIFICE PENILE URETHRA PROSTATIC URTHRA TRIGONE TRIGONE A MEMBRANOUS URETHRA URETHRA Figure 1-59.—Urinary bladder and urethra: A. Frontal section of the female urinary bladder and urethra; B. Frontal section of the male urinary bladder and urethra.

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