The urethra is the vessel responsible for transporting urine from the bladder to an external opening in the perineum. It is lined by stratified columnar epithelium, which is protected from the corrosive urine by mucus secreting glands. In this article, we shall look at the anatomy of the male and female urethra - their anatomical course, neurovascular supply, and any clinical correlations.
The male urethra is approximately 15-20cm long. In addition to urine, the male urethra transports semen - a fluid containing spermatozoa and sex gland secretions. According to the latest classification, the male urethra can be divided anatomically into three parts, from proximal to distal:
The arterial supply to the male urethra is via several arteries:
The nerve supply to the male urethra is derived from the prostatic plexus, which contains a mixture of sympathetic, parasympathetic and visceral afferent fibres.
Lymphatic drainage also varies according to the region of the urethra. The prostatic and membranous portions drain to the obturator and internal iliac nodes, while the penile urethra drains to the deep and superficial inguinal nodes.
Urinary catheterisation is the process of inserting a tube through the urethra and into the bladder. This is typically performed in situations where urine output needs to be monitored (such as sepsis), or when the patient is unable to pass urine (urinary retention). Catheterisation is more complex in males, as there are two angles to consider – the infrapubic and prepubic angles. The prepubic angle can be diminished by holding the penis upwards during urinary catheterisation. It is also important to note the three constrictions in the male urethra – the internal urethral sphincter, external urethral sphincter, and external urethral orifice.
In females, the urethra is relatively short (approximately 4cm). It begins at the neck of the bladder, and passes inferiorly through the perineal membrane and muscular pelvic floor. The urethra opens directly onto the perineum, in an area between the labia minora, known as the vestibule.
Catheterisation of the female urethra is much simpler than the male, as there are no angles to consider, and the direction of the urinary stream is always downward. Additionally, the female urethra is much shorter in length, making it easier to access the bladder.
The anatomy of the male and female urethra is complex and varied. The male urethra is much longer and has multiple functions, including transportation of urine and semen, while the female urethra is significantly shorter and only serves to transport urine. The arterial supply to the male and female urethra is different, with the male urethra receiving its supply from multiple arteries, while the female urethra is supplied by a single artery. The nerve supply and lymphatic drainage of the urethra also vary according to the region. Understanding the anatomy of the male and female urethra is essential for successful urinary catheterisation.
The urethra is an organ that passes through the bladder neck and the pelvic floor, the underside of the body located between the hip bones. In male and female anatomy, the urethra is a thin tube that carries urine from the bladder to the outside of the body. In males, the urethra is longer than females and undergoes several distinct sections and changes as it traverses the body.
In males, the urethra is a tube that is divided into three parts: the prostatic urethra, the membranous urethra and the penile (bulbous) urethra. The prostatic urethra passes through the prostate, a glandular organ located underneath the bladder. It is surrounded by the external urethral sphincter, which provides voluntary control of micturition. The membranous urethra passes through the pelvic floor and the deep perineal pouch and is the narrowest and least dilatable portion of the urethra. The penile (bulbous) urethra passes through the bulb and corpus spongiosum of the penis, ending at the external urethral orifice (the meatus). It receives the bulbourethral glands proximally and in the glans (head) of the penis, the urethra dilates to form the navicular fossa. Some authors consider the part of the urethra that passes through the bladder neck as a fourth anatomic part of the urethra.
The arterial supply to the male urethra is via several arteries. The prostatic urethra is supplied by the inferior vesical artery (branch of the internal iliac artery which also supplies the lower part of the bladder). The membranous urethra is supplied by the bulbourethral artery (branch of the internal pudendal artery) and the penile urethra is supplied directly by branches of the internal pudendal artery. The nerve supply to the male urethra is derived from the prostatic plexus, which contains a mixture of sympathetic, parasympathetic and visceral afferent fibres.
Lymphatic drainage of the male urethra also varies according to the region. The prostatic and membranous portions drain to the obturator and internal iliac nodes, while the penile urethra drains to the deep and superficial inguinal nodes.
Urinary catheterisation is the process of inserting a tube through the urethra and into the bladder. This is typically performed in situations where urine output needs to be monitored (such as sepsis), or when the patient is unable to pass urine (urinary retention). Catheterisation is more complex in males due to the two angles to consider - the infrapubic and prepubic angles. The prepubic angle can be diminished by holding the penis upwards during urinary catheterisation. It is also important to note the three constrictions in the male urethra - the internal urethral sphincter, external urethral sphincter, and external urethral orifice.
In females, the urethra is relatively short (approximately 4cm). It begins at the neck of the bladder, and passes inferiorly through the perineal membrane and muscular pelvic floor. The urethra opens directly onto the perineum, in an area between the labia minora, known as the vestibule. Within the vestibule, the urethral orifice is located anteriorly to the vaginal opening, and 2-3cm posteriorly to the clitoris.
The distal end of the urethra is marked by the presence of two mucous glands that lie either side of the urethra - Skene's glands. They are homologous to the male prostate. The arterial supply to the female urethra is via the internal pudendal arteries, vaginal arteries and inferior vesical branches of the vaginal arteries. Venous drainage is given by veins of the same names. The nerve supply to the female urethra arises from the vesical plexus and the pudendal nerve. Visceral afferents from the urethra run in the pelvic splanchnic nerves.
The lymphatic drainage of the proximal female urethra is to the internal iliac nodes, while the distal urethra drains to the superficial inguinal lymph nodes.
Due to the short length of the urethra, women are more susceptible to infections of the urinary tract. This usually manifests as cystitis, an infection of the bladder. Common symptoms of cystitis are dysuria (pain upon urination), frequency, urgency, and haematuria (blood in the urine). A mid-stream urine sample can be tested for the presence of nitrites and leukocytes (both of which indicate infection).
Simple urinary tract infections are typically treated with a three-day course of antibiotics. However, more complex infections such as those affecting the kidneys often require closer medical supervision and extended courses of antibiotics. Patients who are immunosuppressed or have chronic underlying medical conditions may also need to be closely monitored and treated with more aggressive courses of antibiotics and additional treatments such as urinary antiseptics.
In addition, lifestyle modifications such as increasing water intake, avoiding tight clothing and synthetic fabrics, and wiping the area from front to back after using the bathroom can all help to reduce the risk of urinary tract infections.
In summary, the urethra is an organ that passes through the bladder neck and the pelvic floor. In males, the urethra is divided into three sections, while in females it is relatively short. Its arterial supply is derived from the internal pudendal arteries and its nerve supply from the vesical plexus. Its lymphatic drainage varies according to region. Male catheterisation is more complex due to the two angles to consider, while female urinary tract infections are more common due to the shorter length of the urethra. Appropriate medical care and lifestyle modifications can help to reduce the risk of urinary infections.
