Bladder

The hollow, muscular organ in the lower abdomen that acts as a reservoir for urine. It lies within, and is protected by, the pelvis. An adult bladder can hold about 0.5 litres of urine before the need to pass urine is felt. The bladder walls consist of muscle and an inner lining. Two ureters carry urine to the bladder from the kidneys. At the lowest point of the bladder is the opening into the urethra, which is known as the bladder neck. This is normally kept tightly closed by a ring of muscle (the urethral sphincter). The function of the bladder is to collect and store urine until it can be expelled. Defective bladder function, leading to problems such as incontinence and urinary retention, can have a variety of causes. (See also bladder, disorders of; enuresis).