Urethra

The urethra is a tube-like structure extending from the lower end of the urinary bladder to the external opening for releasing urine out of the body.

In females, the urethra is short and opens just above the vaginal opening, while in males, it traverses through the penis.

The widest region of the male urethra is the prostatic region, passing through the prostate gland below the bladder, followed by the short membranous urethra.

The spongy urethra, the longest part ending in the external urethral orifice, extends through the length of the penis and is surrounded by erectile tissue.

Besides urine, the male urethra also ejaculates semen.

In both sexes, the circular fibers of the detrusor smooth muscle at the bladder-urethra junction thicken to form the internal urethral sphincter.

It is controlled by the autonomic nervous system, preventing urine leakage and maintaining bladder continence.

Another circular band of skeletal muscle surrounds the urethra as it passes through the urogenital diaphragm, forming the external urethral sphincter.

It is under conscious control, allowing voluntary initiation or withholding of urination.