The external urethral orifice is the opening at the terminal end of the urethra, the tube responsible for carrying urine from the bladder out of the body. This opening, also called the urinary meatus, is an anatomical feature in both males and females, though its specific location and certain functions differ between the sexes.
Male External Urethral Orifice Anatomy
The external urethral orifice in males is located at the tip of the glans penis. This opening presents as a vertical, slit-like aperture, though its shape can sometimes be more rounded. The orifice is positioned at the junction where the glans meets the frenular delta, the area of tissue on the underside of the penis. This specific placement and the linear shape of the opening help to create a directed stream during urination.
Surrounding the meatus, the tissue of the glans provides structural support. The orifice is the terminal point of the spongy, or penile, urethra, which is the longest section of the male urethra. This part of the urethra passes through the corpus spongiosum, one of the columns of erectile tissue that make up the penis. The tissue immediately bordering the opening may form two small, lip-like projections that contribute to its slit shape.
The structure of the male urethral orifice is directly continuous with the navicular fossa, a slight widening of the urethra located just before the opening within the glans penis. The entire male urethra, from the bladder to the meatus, measures approximately 18 to 22 centimeters in length.
Female External Urethral Orifice Anatomy
In females, the external urethral orifice is situated within the vulval vestibule, which is the area enclosed by the labia minora. Its specific location is anterior to the vaginal opening and approximately 2.5 centimeters posterior to the clitoris. Unlike the more prominent male meatus, the female orifice is often less immediately visible due to its position within the surrounding vulval structures.
The opening itself appears as a short, sagittal cleft with slightly raised margins. The female urethra is significantly shorter than the male urethra, measuring only about 4 centimeters long.
On either side of the female urethral orifice are the openings for the Skene’s glands, also known as the lesser vestibular glands. These glands are responsible for secreting mucus that provides lubrication to the meatus. The entire structure is protected by the labia, which serve to shield the sensitive openings of the urinary and reproductive tracts.
Functions of the External Urethral Orifice
The primary function of the external urethral orifice in both males and females is to provide a controlled exit point for urine from the body. This action is regulated by the relaxation of sphincter muscles, which allows urine stored in the bladder to flow through the urethra and be expelled. The orifice’s structure helps to direct the flow away from the body.
In males, the external urethral orifice serves a dual purpose, also acting as the exit for semen during ejaculation. This function is distinct from its urinary role, and physiological mechanisms prevent the simultaneous passage of urine and semen.
For females, the function of the external urethral orifice is exclusively urinary. The lubrication provided by the adjacent Skene’s glands helps maintain the health and function of the orifice.
Associated Medical Conditions
Several medical conditions can directly affect the external urethral orifice. Meatal stenosis is a condition characterized by the narrowing of the meatus, which can obstruct the flow of urine and lead to difficulty urinating. This can occur in both males and females but is more commonly diagnosed in males. It may result from inflammation, injury, or be a complication of procedures like circumcision.
Congenital conditions can also impact the location of the urethral orifice in males. Hypospadias is a developmental anomaly where the meatus is located on the underside of the penis, rather than at the tip. Epispadias is a rarer condition where the opening is situated on the upper aspect of the penis. Both conditions affect the direction of the urinary stream and may require surgical correction.
Inflammation of the urethra, known as urethritis, can cause symptoms that manifest at the orifice, such as pain, burning during urination, or discharge. Urinary tract infections (UTIs) can also produce symptoms localized to the meatus, as the opening is the exit point of the infected urinary tract.