The urethra is a tube that carries urine from the bladder to outside the body. Part of the broader urinary system, this passageway is located in the pelvic region. Its walls are composed of thin layers of epithelial tissue, smooth muscle, and connective tissue. Two sphincter muscles, an internal one where the urethra leaves the bladder and an external one in the pelvic floor, act as valves to control the release of urine. When the bladder is full, it signals the brain, and these muscles work together to allow urination.
The Male Urethra
The male urethra is a fibromuscular tube approximately 18 to 22 centimeters long. It serves a dual role, acting as a conduit for both urine from the bladder and semen during ejaculation. The tube extends from the bladder neck, passing through the prostate gland and the penis, and ending at the external urethral orifice. When the penis is not erect, the urethra has a distinct double curvature.
Its significant length means it is divided into distinct anatomical sections. The first part is the prostatic urethra, which is about 3 to 4 centimeters long and passes through the prostate gland. This section is the widest part of the male urethra and contains the urethral crest. It is here that the ejaculatory ducts connect, allowing semen to enter the urethra.
Following the prostate, the urethra becomes the membranous urethra. This is the shortest and narrowest part, measuring about 1 to 1.5 centimeters. It passes through the deep perineal pouch and is surrounded by the external urethral sphincter for voluntary control over urination. The final and longest section is the spongy urethra, which is about 15 cm long and travels through the corpus spongiosum.
The Female Urethra
The female urethra is substantially shorter than its male counterpart, measuring only about 4 centimeters in length. Its sole function is to transport urine from the bladder out of the body. The tube begins at the base of the bladder, known as the bladder neck, and extends downward through the pelvic floor muscles.
The external opening of the female urethra is located within the vulvar vestibule, between the clitoris and the vaginal opening. The urethra is lined with epithelial cells and contains glands that secrete mucus, which helps protect the lining from urine. A muscular sphincter helps to keep urine inside the body until it is voluntarily released.
Because the female urethra is short and its opening is near the anus, there is a greater risk of bacteria, such as Escherichia coli, being transferred from the gastrointestinal tract. This anatomy makes it easier for bacteria to travel into the bladder, a primary reason why urinary tract infections (UTIs) are more common in females. Sexual activity can also increase the risk.
Common Urethral Conditions
One of the most frequent conditions is urethritis, which is the inflammation of the urethra. Urethritis is a form of urinary tract infection (UTI) and can result from bacterial or viral infections, including STIs like chlamydia and gonorrhea. When bacteria enter the urethra, they can multiply and ascend to infect the bladder (cystitis) and potentially the kidneys. Symptoms often include a burning sensation during urination, an increased urge to urinate, and discharge.
Another condition is a urethral stricture, a narrowing of the urethra caused by the formation of scar tissue. This scarring can develop after an injury or from inflammation related to long-term infections. A stricture restricts urine flow, leading to symptoms like a weak or spraying urine stream, straining to urinate, and the feeling of incomplete bladder emptying. In men, strictures are most often found in the bulbar urethra.
When to Seek Medical Attention
It is advisable to consult a healthcare provider if you experience symptoms that suggest a urethral problem. Warning signs include a burning sensation or pain during urination, which could indicate inflammation or infection. A noticeable change in your urine stream, such as it becoming weak, slow, or spraying, may point to a physical obstruction like a stricture. The frequent and urgent need to urinate, any unusual discharge, or the presence of blood in the urine (hematuria) or semen should also be evaluated by a professional, as should difficulty starting urination or pain in the lower abdomen.