Anatomy of the Urethra Female urethra: 4 cm long Straight One part only Male urethra: 18-20 cm long S-shaped, formed of 4 parts Parts: Preprostatic part: 1-1.5 cm in length. • From the bladder neck to the superior aspect of the prostate. • It is surrounded by the involuntary internal urethral sphincter, which is controlled by the autonomic nervous system. • Its contraction prevents the retrograde ejaculation into the bladder 21 Prostatic urethra Length: It is 3-4 cm long. • It passes downwards and forwards through the substance of the prostate. • It is the widest and most dilatable part of the urethra. The posterior wall of the prostatic urethra shows: • Urethral crest: a prominent longitudinal fusiform median ridge. • Seminal colliculus: a rounded elevation in the middle of the urethral crest. It is called membranous because it lies in the deep perineal pouch 22 Prostatic Urethra Seminal colliculus: shows 3 openings: 1)Prostatic utricle: It is a small diverticulum homologues to the uterus in female. 2) The openings of the two ejaculatory ducts: on each side of the prostatic utricle. 3) Prostatic sinus: a groove on each side of the urethral crest. It receives the openings of 15-20 prostatic ducts from the prostatic glands. 23 Membranous Urethra Membranous urethra: It is the shortest part (1.5 cm), and the narrowest part (with the exception of the external urethral orifice). It begins at the lower part of the prostate. Membranous urethra: It is surrounded by the sphincter urethrae muscle, which is the voluntary external urethral sphincter supplied by the pudendal nerve. •There are 2 small bulbourethral glands on either side of the membranous urethra 24 Penile (Spongy) Urethra Penile (spongy) urethra: • It is 15 cm long. • It extends from the end of the membranous urethra to the external urethral orifice on the glans penis. • At its beginning it enters the upper surface of the bulb penis (which lies in the superficial perineal pouch). Membranous urethra passes through the body and the glans penis. It ends by opening to the outside through the external urethral meatus which is the narrowest point of the whole urethra. 25 Female Urethra Female urethra: • It is a short duct only 4 cm long. • It begins at the internal urethral orifice at the bladder neck, which is surrounded by the internal urethral sphincter, and runs downwards and forwards, traversing the deep perineal pouch and perineal membrane to open in the vestibule immediately in front of the opening of the vagina. • The upper part is surrounded by sphincter urethrae muscle which is the voluntary external urethral sphincter. generate picture explaining all

Prostatic urethra Length: It is 3-4 cm long. • It passes downwards and forwards through the substance of the prostate. • It is the widest and most dilatable part of the urethra. The posterior wall of the prostatic urethra shows: • Urethral crest: a prominent longitudinal fusiform median ridge. • Seminal colliculus: a rounded elevation in the middle of the urethral crest. It is called membranous because it lies in the deep perineal pouch 22 Prostatic Urethra Seminal colliculus: shows 3 openings: 1)Prostatic utricle: It is a small diverticulum homologues to the uterus in female. 2) The openings of the two ejaculatory ducts: on each side of the prostatic utricle. 3) Prostatic sinus: a groove on each side of the urethral crest. It receives the openings of 15-20 prostatic ducts from the prostatic glands. 23 Membranous Urethra Membranous urethra: It is the shortest part (1.5 cm), and the narrowest part (with the exception of the external urethral orifice). It begins at the lower part of the prostate. Membranous urethra: It is surrounded by the sphincter urethrae muscle, which is the voluntary external urethral sphincter supplied by the pudendal nerve. •There are 2 small bulbourethral glands on either side of the membranous urethra 24 Penile (Spongy) Urethra Penile (spongy) urethra: • It is 15 cm long. • It extends from the end of the membranous urethra to the external urethral orifice on the glans penis. • At its beginning it enters the upper surface of the bulb penis (which lies in the superficial perineal pouch). Membranous urethra passes through the body and the glans penis. It ends by opening to the outside through the external urethral meatus which is the narrowest point of the whole urethra. 25 Female Urethra Female urethra: • It is a short duct only 4 cm long. • It begins at the internal urethral orifice at the bladder neck, which is surrounded by the internal urethral sphincter, and runs downwards and forwards, traversing the deep perineal pouch and perineal membrane to open in the vestibule immediately in front of the opening of the vagina. • The upper part is surrounded by sphincter urethrae muscle which is the voluntary external urethral sphincter. generate picture explaining all