Male - Urethra

1. Overview

The male urethra is a tubular structure that serves as the passageway for both urine and semen to exit the body. It is an essential part of the male reproductive and urinary systems, as it provides a dual function: the excretion of urine from the bladder and the transport of semen during ejaculation. The urethra is unique in its ability to carry both urine and sperm, but not simultaneously. It is the final segment of the male urinary system and also plays a key role in sexual function.

2. Location

The male urethra extends from the internal urethral orifice in the bladder to the external urethral orifice at the tip of the glans penis. It passes through the prostate gland, the urogenital diaphragm, and the penis itself. The urethra is divided into several regions based on its anatomical course:

• Prostatic urethra: The portion of the urethra that runs through the prostate gland. It is approximately 3–4 cm in length and serves as the first section of the urethra.

• Membranous urethra: The shortest and most vulnerable segment, located between the prostate and the bulb of the penis. It passes through the urogenital diaphragm.

• Penile (spongy) urethra: The longest section, running through the corpus spongiosum of the penis, ending at the external urethral orifice at the glans penis.

3. Structure

The male urethra has a complex structure that allows it to fulfill both its urinary and reproductive roles:

• Epithelium: The urethra is lined by transitional epithelium in the prostatic portion, which changes to pseudostratified columnar epithelium in the membranous and penile parts. The epithelium helps prevent damage to the urethral walls and facilitates the smooth passage of urine and semen.

• Muscle layers: The walls of the urethra contain smooth muscle fibers that form a sphincter at the base of the bladder (internal urethral sphincter), which helps control urine flow. The external sphincter, located in the urogenital diaphragm, is composed of skeletal muscle and allows voluntary control of urination.

• Urethral glands: The urethra contains small glands, such as the bulbourethral glands (Cowper's glands), which secrete lubricating fluid to protect sperm during ejaculation. The mucous secretion also helps lubricate the passage for urine excretion.

• Corpus spongiosum: The penile portion of the urethra runs through the corpus spongiosum, a spongy tissue that helps prevent the urethra from being compressed during erection, ensuring that semen can be expelled during ejaculation.

4. Function

The primary functions of the male urethra are related to both the urinary and reproductive systems:

• Urinary function: The urethra serves as the conduit for urine to be expelled from the bladder during urination. The internal and external sphincters control the flow of urine, allowing voluntary and involuntary control of urination.

• Reproductive function: The urethra also acts as the passage for semen during ejaculation. The semen travels through the urethra from the prostate and seminal vesicles to the external urethral orifice at the tip of the penis.

5. Physiological Role(s)

The male urethra is critical for maintaining both urinary and reproductive health:

• Urinary control: The urethra is essential for regulating the release of urine from the bladder. The sphincters help prevent incontinence, allowing for controlled urination when appropriate.

• Sexual function: The urethra facilitates the transport of semen during ejaculation, ensuring that sperm are expelled effectively from the body. Its structure and function are vital for the delivery of sperm into the female reproductive tract for potential fertilization.

• Protection of sperm: The bulbourethral glands secrete a clear, alkaline fluid that neutralizes any acidity in the urethra, providing protection for sperm before ejaculation. This fluid also lubricates the urethra for smooth semen passage.

6. Clinical Significance

The male urethra is involved in several clinical conditions that can affect both urinary and reproductive function:

• Urethritis: Inflammation of the urethra, often caused by bacterial infections such as gonorrhea or chlamydia. Symptoms include painful urination, discharge, and itching. Untreated urethritis can lead to complications like prostatitis or infertility.

• Benign prostatic hyperplasia (BPH): Enlargement of the prostate gland can compress the prostatic urethra, causing urinary symptoms like frequent urination, weak urine stream, and incomplete bladder emptying. BPH can affect quality of life and may require medical or surgical treatment.

• Urethral stricture: A narrowing of the urethra due to scarring from infections, trauma, or surgeries. This can result in difficulty urinating, urinary retention, and discomfort. Treatment options include urethral dilation or surgical repair.

• Phimosis and paraphimosis: These conditions involve the foreskin (prepuce), but they can affect the external opening of the urethra. Phimosis prevents the foreskin from retracting, while paraphimosis refers to the inability to return the retracted foreskin to its original position, leading to swelling and pain at the urethral opening.

• Urethral cancer: A rare form of cancer that can affect the male urethra, often leading to symptoms such as blood in the urine, pain, or lumps in the urethral area. Early detection and treatment are essential for successful management.

• Priapism: A prolonged erection that may be accompanied by pain and difficulty with urination, particularly if there is significant swelling. Priapism can interfere with normal urethral function and cause damage if untreated.

• Sexually transmitted infections (STIs): The urethra is a common site of infection for various STIs, including gonorrhea, chlamydia, and herpes. Infections in the urethra can lead to pain, discharge, and potential long-term complications like infertility.

Maintaining good urinary and sexual health requires attention to proper hygiene, regular check-ups, and prompt treatment for infections or symptoms that may indicate problems with the urethra. Early intervention can prevent long-term complications and preserve reproductive health.