SN5
SHORT NOTE
5M
★ High-yield
Describe the male urethra with its parts and constrictions. Add a note on its rupture and the extravasation of urine.
Definition
The male urethra is about 18–20 cm long, extending from the internal urethral orifice at the neck of the bladder to the external urethral meatus at the tip of the glans penis.
- It serves both the urinary and the genital systems
Parts
| Part | Length | Features |
|---|---|---|
| Prostatic | 3–4 cm | The widest and most dilatable. Bears the urethral crest with the colliculus seminalis (verumontanum), on which open the ejaculatory ducts and the prostatic utricle; prostatic ducts open in the grooves beside it |
| Membranous | 1–2 cm — the shortest | The narrowest and least dilatable part; passes through the urogenital diaphragm, surrounded by the sphincter urethrae. Fixed and therefore vulnerable |
| Spongy (penile) | 15 cm — the longest | Traverses the corpus spongiosum. Dilated at the bulb and at the navicular fossa in the glans; bulbourethral (Cowper) ducts open into it |
- The external meatus is the narrowest point of all, which is why a catheter that passes the meatus will usually pass the whole urethra
Curves and Constrictions
| Narrow points, from within outward |
|---|
| Internal urethral orifice |
| Membranous urethra — the narrowest fixed part |
| External urethral meatus — the narrowest of all |
Rupture of the Urethra
| Feature | Rupture of the bulbar urethra | Rupture of the membranous urethra |
|---|---|---|
| Mechanism | Fall astride a bar or bicycle crossbar | Fracture of the pelvis |
| Site | Below the perineal membrane | At the urogenital diaphragm |
| Urine extravasates into | Superficial perineal pouch → scrotum, penis and anterior abdominal wall (deep to Scarpa fascia) | Retropubic space (extraperitoneal), around the bladder |
| Spreads into the thigh? | NO — Colles fascia is attached to the ischiopubic rami and the fascia lata | — |
| Sign | Butterfly-shaped perineal bruising; blood at the meatus | High-riding prostate on rectal examination |
- Blood at the external meatus is the cardinal sign, and is an absolute contraindication to attempted catheterisation — a suprapubic catheter must be used instead
Applied Aspects
- Catheterisation — strict asepsis, generous lubricant, and the penis held vertically then lowered as the catheter passes the bulb; force must never be used at the membranous urethra
- Urethral stricture — commonest after trauma, instrumentation or gonococcal urethritis; causes a poor stream and eventually retention
- Hypospadias — failure of the urethral folds to fuse, so the meatus opens on the ventral surface; associated with chordee
- The female urethra is only 4 cm long, straight and dilatable, which is why urinary tract infection is far commoner in women and catheterisation far easier
- Rupture of the penile urethra may accompany fracture of the penis, and requires urethrography before any instrumentation
All questions in Pelvis & Perineum
- Q1Describe the bony pelvis with its divisions and diameters. Add a note on the types of pelvis and the sex differences. ★
- Q2Describe the pelvic diaphragm with its parts and functions. Add a note on the perineum, the perineal pouches and the perineal body. ★
- Q3Describe the urinary bladder under relations, interior, blood supply and nerve supply. Add a note on micturition and its disorders. ★
- Q4Describe the uterus under position, supports, relations and blood supply. Add a note on its applied anatomy. ★
- Q5Describe the rectum and anal canal. Explain the importance of the pectinate line and add a note on the ischiorectal fossa. ★
- SN1Describe the prostate with its lobes, zones, relations and applied anatomy. ★
- SN2Describe the course, branches and applied anatomy of the pudendal nerve. ★
- SN3Describe the boundaries and contents of the ischiorectal fossa. Add a note on ischiorectal abscess. ★
- SN4Describe the broad ligament with its parts and contents. Add a note on the ovary and uterine tube. ★
- SN5Describe the male urethra with its parts and constrictions. Add a note on its rupture and the extravasation of urine. ★
- SN6Describe the internal iliac artery with its branches and collateral circulation. ★
- SN7Describe the sacrum with its features. Add a note on caudal anaesthesia and the sacro-iliac joint.