Urethra

Urethra:

Conducts urine from the urinary bladder to the external environment.
Passes through the perineal membrane, which is a thick layer of connective tissue that supports the pelvic structures.
Sphincters regulate the passage of urine through the urethra.
Lies just posterior to pubic bones in anterior pelvis.

Female urethra

Key features:

Lies anterior to the opening of the vagina.
External urethral orifice opens to vestibule of the vagina.
External urethral sphincter lies superior to/deep to perineal membrane;

Existence of internal urethral sphincter is contested (if it exists, would be at neck of bladder and enclose internal urethral orifice)

Enclosed by labia minora and labia majora, which are flaps of skin.
3-5 cm in length.

Male urethra

Key features:

Comprises 3 continuous segments:

— Prostatic, which passes through the prostate gland, — Membranous, aka intermediate, and, — Spongy, aka, penile, which passes through the corpus spongiosum of the penis.

Conducts both urine and semen.
Internal urethral orifice and sphincter at neck of bladder
External urethral sphincter lies superior to/deep to perineal membrane
External urethral orifice is located at tip of penis
18-20 cm long

Clinical correlations:

Urinary incontinence (aka, urine leakage) is common, especially in women. The pathogenesis is often an inability to close the urethral orifices, which commonly occurs from weakened pelvic muscles or nerve damage.
Benign prostatic hyperplasia (BPH), which is common amongst older men. The pathogenesis is that the prostate gland enlarges, pinches off the urethra, which impairs urination, and urine retention in the bladder can result.

Urethra

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