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
Detailed anatomical diagram of male and female urethra side by side, labeled cross-section and longitudinal view. LEFT SIDE - MALE URETHRA (18-20 cm, S-shaped): Draw a sagittal section of the male pelvis showing all 4 parts of the urethra in different colors: 1. PREPROSTATIC PART (1-1.5 cm) - at bladder neck, surrounded by internal urethral sphincter (involuntary, autonomic), label "prevents retrograde ejaculation" 2. PROSTATIC URETHRA (3-4 cm) - widest and most dilatable part, passing through prostate gland. Show posterior wall with: - Urethral crest (longitudinal median ridge) - Seminal colliculus (rounded elevation) with 3 openings: prostatic utricle (homologue of uterus), two ejaculatory duct openings, prostatic sinus (receives 15-20 prostatic ducts) 3. MEMBRANOUS URETHRA (1.5 cm) - shortest and narrowest part (except external meatus), in deep perineal pouch, surrounded by sphincter urethrae (voluntary external sphincter, pudendal nerve), bulbourethral glands on either side 4. PENILE/SPONGY URETHRA (15 cm) - enters bulb of penis in superficial perineal pouch, passes through corpus spongiosum and glans penis, ends at external urethral meatus (narrowest point) RIGHT SIDE - FEMALE URETHRA (4 cm, straight): Draw sagittal section showing: - Short, straight duct 4 cm long - Starts at bladder neck (internal urethral orifice) surrounded by internal urethral sphincter - Runs downward and forward through deep perineal pouch and perineal membrane - Upper part surrounded by sphincter urethrae (voluntary external sphincter) - Opens in vestibule anterior to vaginal opening Use clear anatomical illustration style with clean labels, color-coded parts, arrows, and a comparison table at the bottom showing: Female (4cm, straight, 1 part) vs Male (18-20cm, S-shaped, 4 parts). Medical textbook style, white background, professional anatomy diagram.
| Part | Length | Key Feature |
|---|---|---|
| Preprostatic | 1-1.5 cm | Internal sphincter (involuntary) - prevents retrograde ejaculation |
| Prostatic | 3-4 cm | Widest & most dilatable; urethral crest, seminal colliculus, prostatic sinus |
| Membranous | 1.5 cm | Shortest & narrowest (except meatus); external sphincter (voluntary, pudendal n.); bulbourethral glands |
| Penile/Spongy | 15 cm | Longest; ends at external urethral meatus (narrowest point overall) |
- Prostatic utricle (homologue of female uterus)
- Two ejaculatory duct openings
- Prostatic sinuses (receive 15-20 prostatic ducts)
- Runs from bladder neck through deep perineal pouch to vestibule (anterior to vaginal opening)
- Internal sphincter at bladder neck (involuntary)
- External sphincter (sphincter urethrae) around upper part (voluntary, pudendal nerve)
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
Detailed medical anatomy diagram showing the prostatic urethra, membranous urethra, penile (spongy) urethra, and female urethra. Clean medical textbook illustration style on white background with clear labels and arrows. TOP SECTION - PROSTATIC URETHRA (zoomed cross-section and longitudinal view): Draw a magnified longitudinal section of the prostatic urethra (3-4 cm) inside the prostate gland. Show: - The posterior wall with the URETHRAL CREST (a prominent longitudinal fusiform median ridge, shown as a raised ridge in the midline) - The SEMINAL COLLICULUS (a rounded elevation on the urethral crest) with 3 clearly labeled openings: * CENTER: Prostatic utricle (small blind-ending diverticulum, labeled "homologue of female uterus") * LEFT and RIGHT of utricle: Two ejaculatory duct openings (one on each side) * PROSTATIC SINUS: grooves on each side of the urethral crest receiving 15-20 prostatic duct openings (shown as small dots) - Label the prostate gland surrounding the urethra - Label this as "Widest and most dilatable part" MIDDLE LEFT - MEMBRANOUS URETHRA: Draw a short segment (1.5 cm) showing: - Located in the deep perineal pouch (label the perineal pouch) - Surrounded by SPHINCTER URETHRAE MUSCLE (voluntary external urethral sphincter) - show as a circular muscle ring with label "Supplied by Pudendal Nerve (voluntary)" - Two BULBOURETHRAL GLANDS (Cowper's glands) - small round glands on either side - Label: "Shortest part (1.5 cm)" and "Narrowest part (except external meatus)" - Arrow showing it begins at lower part of prostate MIDDLE RIGHT - PENILE (SPONGY) URETHRA: Draw a longitudinal section of the penis showing: - 15 cm long urethra running through corpus spongiosum - Enters at upper surface of bulb of penis (in superficial perineal pouch) - label this - Passes through body of penis and glans penis - Ends at EXTERNAL URETHRAL MEATUS on tip of glans penis - Label: "Narrowest point of the whole urethra" with arrow at external meatus - Show corpus spongiosum surrounding the urethra BOTTOM - FEMALE URETHRA (sagittal section of female pelvis): Draw a sagittal view showing: - Bladder above - SHORT straight urethra (4 cm) running downward and forward - INTERNAL URETHRAL SPHINCTER at bladder neck (involuntary, shown as inner muscle layer) - Path through deep perineal pouch and perineal membrane (label both) - SPHINCTER URETHRAE surrounding upper part (voluntary external sphincter, labeled) - Urethra opening in the VESTIBULE, immediately anterior to vaginal opening - Show vagina behind and urethra in front, both opening into vestibule - Label: "4 cm long, straight" Use different colors for each section: blue for prostatic, green for membranous, orange for penile/spongy, pink for female. Add a small comparison box: Male urethra = 18-20cm, S-shaped, 4 parts vs Female = 4cm, straight, 1 part.
- Widest & most dilatable part
- Posterior wall: Urethral crest → Seminal colliculus → 3 openings (prostatic utricle center, ejaculatory ducts on each side, prostatic sinuses receiving 15-20 prostatic ducts)
- Shortest & narrowest (except external meatus)
- In deep perineal pouch
- External sphincter = sphincter urethrae (voluntary, pudendal nerve)
- Bulbourethral glands on either side
- Enters bulb of penis (superficial perineal pouch)
- Runs through corpus spongiosum → glans penis
- External urethral meatus = narrowest point of entire urethra
- Straight, single part
- Internal sphincter at bladder neck (involuntary)
- External sphincter around upper part (voluntary, pudendal nerve)
- Opens in vestibule, anterior to vaginal opening