The Lower Urinary Tract: Anatomy
The lower urinary tract consists of the bladder, which serves to store urine, and the urethra, which acts as a drainage tube for urine to exit the body. Storage and emptying of the bladder are regulated by the internal and external urethral sphincters. Successful micturition results from appropriate interaction between the bladder muscle and supporting neurovascular structures. The muscular bladder wall contracts, internal and external sphincters are relaxed, and urine is expulsed through the urethra.
The normal bladder is a hollow, highly compliant organ that can comfortably hold approximately 500 mL of urine when full. When empty, it lies as a pyramid-shaped viscus within the pelvic cavity between the pubis and rectum in the male, and between the pubis and uterus in the female. As it fills with urine, it rises above the pelvis minor toward the abdomen and becomes more rounded in shape.
The bladder can be divided into two main parts: the body, where urine is collected and stored, and the neck, which traverses the urogenital diaphragm to connect with the urethra (Fig. 32.1). Superiorly, the body of the bladder is covered with peritoneum. The apex of the bladder body ends as a fibrous cord, a derivative of the urachus called the median umbilical ligament. This extends from the apex to the umbilicus between the transversalis fascia and the peritoneum. Posteriorly, the base of the bladder body lies adjacent to the rectum, and in males, it is separated from the ...