Male genital organs
Male Genital Organs: Testis, Epididymis, Vas Deferens, Scrotum and Penis
Male genital anatomy for FCPS Part 1: scrotal and cord coverings, testis, epididymis, vas, accessory glands and penis, with blood, lymph and nerve supply. Explains torsion, hydrocele, varicocele, tumours, infertility, priapism and penile injury.
Scrotum and coverings of the cord
- Layers from outside: skin, dartos (smooth muscle in superficial fascia), external spermatic fascia, cremasteric muscle and fascia, internal spermatic fascia, tunica vaginalis (parietal and visceral), tunica albuginea of the testis.
| Cord covering | Derived from |
|---|---|
| External spermatic fascia | External oblique aponeurosis |
| Cremaster muscle and fascia | Internal oblique |
| Internal spermatic fascia | Transversalis fascia |
| (none) | Transversus abdominis gives no covering |
- Scrotal skin drains to superficial inguinal nodes. The scrotum is kept 2–3 °C below core by the pampiniform plexus (countercurrent exchange), dartos and cremaster.
Development and descent
- The testis develops on the posterior abdominal wall at about L1, so its vessels, nerves and lymph come from there.
- The gubernaculum guides descent; it passes the deep ring at about 7 months and reaches the scrotum by birth. In the male it remains as the scrotal ligament; in the female it becomes the ovarian and round ligaments.
- A patent processus vaginalis gives an indirect inguinal hernia (contents inside the cord coverings) or a congenital hydrocele.
- Undescended testis: infertility and germ cell tumour risk (seminoma); orchidopexy at 6–12 months. Retractile testes are normal.
Testis and epididymis
- Tunica albuginea sends septa into about 250 lobules of seminiferous tubules; sperm pass through straight tubules, rete testis, efferent ductules, then the epididymis.
- Spermatogenesis takes about 64–74 days; sperm mature and become motile in the epididymis.
- Testicular artery from the aorta at L2; also cremasteric and artery to the vas.
- Pampiniform plexus forms the testicular vein: right to IVC, left to left renal vein at a right angle. Varicocele is mostly left.
- Lymph to para-aortic nodes (L1–L2), not inguinal unless scrotal skin is invaded; so never biopsy a testis through the scrotum (inguinal orchidectomy).
- Nerves: sympathetic T10. Visceral afferents enter the cord at T10, so early torsion can present as periumbilical pain and vomiting before scrotal pain is obvious; ureteric colic radiates the other way, to the testis.
Vas deferens and accessory glands
| Structure | Key facts |
|---|---|
| Vas deferens | Narrow star-shaped lumen, pseudostratified columnar epithelium with stereocilia, very thick three-layered smooth muscle; in the cord, through the inguinal canal, crosses over the ureter, joins the seminal vesicle duct as the ejaculatory duct |
| Epididymis | Same epithelium with long stereocilia but a thin muscle coat, many tubule profiles |
| Seminal vesicles | About 60–70% of semen volume; alkaline, fructose-rich |
| Prostate | Acidic fluid with citrate, zinc, PSA |
| Bulbourethral (Cowper) glands | Deep perineal pouch; pre-ejaculatory mucus |
- Vasectomy: divides the vas in the upper scrotum. Ejaculate then contains prostatic and seminal vesicle secretions without sperm, but stored sperm persist for weeks, so clearance is confirmed by semen analysis (about 12 weeks).
- Congenital bilateral absence of the vas deferens: impalpable vasa, normal testes, normal FSH and testosterone, low-volume (< 1 mL) acidic, fructose-poor ejaculate with no sperm (seminal vesicles are absent or blocked). Test the CFTR gene, even without lung disease.
- Azoospermia with normal testis size and hormones means obstruction (vas, epididymis, ejaculatory ducts); small testes with high FSH mean testicular failure (e.g. Klinefelter 47,XXY: small firm testes, gynaecomastia, long legs).
Nerves of emission, ejaculation and erection
| Event | Nerve |
|---|---|
| Erection | Parasympathetic, pelvic splanchnics S2–S4 (cavernous nerves): "point" |
| Emission (semen into the urethra) | Sympathetic T11–L2 via the superior hypogastric plexus; closes the bladder neck |
| Ejaculation | Pudendal nerve: rhythmic bulbospongiosus contraction |
- After aortic surgery at the bifurcation, preserved erections with dry orgasm point to damage to the superior hypogastric plexus (sympathetic), not the parasympathetic supply.
Penis
- Three erectile bodies: paired corpora cavernosa (dorsal) and the corpus spongiosum (ventral, carrying the urethra, expanding as the glans and bulb).
- Each body is wrapped in tunica albuginea; all three are enclosed by deep (Buck's) fascia, then superficial (Colles'/dartos) fascia.
- Penile fracture: rupture of the tunica albuginea of a corpus cavernosum during forced bending of the erect penis. If Buck's fascia stays intact, the haematoma is confined to the shaft (aubergine deformity); blood at the meatus suggests urethral injury.
- Peyronie disease: fibrous plaque in the tunica albuginea of the corpora cavernosa, usually dorsal, causing painful curvature.
- Ischaemic priapism (sickle cell disease): only the corpora cavernosa are engorged; the glans and spongiosum stay soft; aspirated blood is dark and hypoxic. Beyond about 24 hours, fibrosis and erectile dysfunction follow.
Scrotal swellings and emergencies
| Condition | Clue |
|---|---|
| Testicular torsion | Teenager, sudden severe pain and vomiting, high horizontal testis, absent cremasteric reflex; bell-clapper anomaly (tunica vaginalis surrounds the whole testis); urgent exploration within 6 hours, fix both sides |
| Torsion of appendix testis (hydatid of Morgagni) | Tender nodule at the upper pole, blue dot, cremasteric reflex present; explore if cord torsion cannot be excluded |
| Epididymo-orchitis | Gradual onset, fever, dysuria |
| Hydrocele | Fluid in tunica vaginalis; transilluminates; can get above it; testis impalpable inside |
| Haematocele | Blood in tunica vaginalis after trauma; tense, tender, does not transilluminate |
| Varicocele | "Bag of worms", left side, empties lying down |
| Epididymal cyst | Separate, above and behind the testis; transilluminates |
| Testicular tumour | Painless hard lump in the testis; does not transilluminate |
Testicular tumours
| Tumour | Markers and features |
|---|---|
| Seminoma | Older (30s–40s); LDH may rise, AFP normal; very radiosensitive |
| Non-seminomatous germ cell tumours (embryonal, yolk sac, choriocarcinoma, teratoma) | AFP (yolk sac) and β-hCG (choriocarcinoma) raised |
| Yolk sac tumour | Commonest in children under 3; AFP; Schiller–Duval bodies |
| Spermatocytic tumour | Elderly men |
Remember The testis remembers it began at L1: aortic artery, renal or caval vein, para-aortic nodes, T10 pain.
Exam trap Raised AFP excludes pure seminoma; think non-seminomatous germ cell tumour.
Exam trap Internal spermatic fascia comes from transversalis fascia; transversus abdominis gives no layer.
How FCPS asks about this
- Gubernaculum in the male becomes: scrotal ligament.
- Torsion anatomy and management: bell-clapper deformity; immediate exploration and bilateral fixation.
- Periumbilical pain in early torsion: visceral afferents entering the cord at T10.
- Thick three-layer muscle with stereocilia: vas deferens (epididymis has thin muscle).
- Absent vasa with acidic low-volume azoospermia: CFTR mutation.
- Dry orgasm after aortic surgery: superior hypogastric plexus injury.
- Penile haematoma confined to shaft: Buck's fascia intact.
Test yourself on this topic
5 of the 56 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
After forcible bending of the erect penis during intercourse, a man has a swollen, bruised penile shaft and blood at the meatus. The scrotum and perineum are not swollen. Which layer has confined the blood and urine to the shaft?
Answer: Deep (Buck's) fascia of the penis
This is a penile fracture: rupture of the tunica albuginea of the corpus cavernosum, sometimes with urethral injury. The deep fascia of the penis (Buck's fascia) encloses the corpora cavernosa and corpus spongiosum. While it remains intact, blood and extravasated urine stay within it, so swelling is limited to the shaft, giving an 'aubergine' penis. If Buck's fascia is also torn, fluid spreads under the membranous (Colles) fascia into the scrotum, perineum and lower abdominal wall, as in bulbar urethral injury.
Penile fascial layers
- Buck's fascia surrounds all three corpora
- Intact: swelling limited to the shaft
- Torn: spreads under Colles fascia
- To scrotum, perineum, abdominal wall
Remember Shaft-only swelling: Buck's fascia is holding.
Exam trap Blood at the meatus with a penile fracture suggests urethral injury and needs urethral assessment.
Why the other options are wrong
- Membranous (Colles) fascia Limits spread once Buck's fascia is breached, giving scrotal and perineal swelling.
- Tunica albuginea of the testis Covers the testis, not the penis.
- Dartos layer of the scrotum Lies in the scrotal wall; would allow scrotal spread.
- Perineal membrane Limits spread upwards from the superficial pouch, not along the shaft.
A 10-year-old boy has scrotal pain for one day. The testis itself is not tender and the cremasteric reflex is present, but there is a small tender nodule at the upper pole with a blue spot seen through the skin. Which of the following structures has twisted?
Answer: Appendix testis
The appendix testis (hydatid of Morgagni) is a small remnant of the paramesonephric (Müllerian) duct attached to the upper pole of the testis. It can twist, especially before puberty, causing a tender nodule at the upper pole that may show through the skin as a blue dot. The testis is not tender and the cremasteric reflex is preserved, unlike torsion of the spermatic cord. It settles with rest and analgesia, but if testicular torsion cannot be excluded the scrotum is explored. The appendix of the epididymis is a mesonephric remnant.
Appendix testis
- Müllerian remnant at the upper pole
- Twists before puberty
- Blue dot sign
- Testis not tender, reflex present
Remember Blue dot at the upper pole: twisted appendix testis.
Exam trap If cord torsion cannot be excluded clinically, explore the scrotum rather than wait.
Why the other options are wrong
- Spermatic cord Cord torsion makes the whole testis tender, high and loses the cremasteric reflex.
- Appendix of the epididymis A mesonephric remnant on the epididymal head; much less often twisted.
- Tunica vaginalis Does not twist on its own.
- Gubernaculum Becomes the scrotal ligament; does not twist.
A 17-year-old boy with sickle cell disease has a painful erection for 6 hours. The shaft is rigid but the glans is soft. Aspirated blood is dark. Which of the following erectile tissues is engorged?
Answer: Corpora cavernosa only
In ischaemic (low-flow) priapism, venous outflow from the corpora cavernosa is blocked, here by sickled cells, so blood stagnates, becomes hypoxic and acidotic, and the tissue is at risk of fibrosis. The corpora cavernosa form the rigid dorsal bodies of the shaft. The corpus spongiosum, which surrounds the urethra and expands into the glans, has separate drainage and is usually spared, so the glans stays soft and urination is usually possible. Aspiration of dark blood confirms the low-flow type, which is an emergency.
Priapism
- Low-flow: venous outflow blocked
- Affects corpora cavernosa
- Glans soft: spongiosum spared
- Dark blood; emergency within hours
Remember Hard shaft, soft glans: cavernosal priapism.
Exam trap Delay beyond 24 hours in ischaemic priapism often leads to fibrosis and erectile dysfunction.
Why the other options are wrong
- Corpus spongiosum only Usually spared, which is why the glans is soft.
- All three corpora The spongiosum is not involved.
- Bulb of the penis only Part of the spongiosum; not engorged here.
- Glans and corpus spongiosum These are spared in ischaemic priapism.
A transilluminable scrotal swelling lies above and behind the testis, which is felt separately. What is the most likely diagnosis?
Answer: Epididymal cyst
An epididymal cyst (or spermatocele, which contains sperm) arises from the epididymis, which lies along the posterior border of the testis with its head at the upper pole. The swelling is therefore felt above and behind the testis and separate from it, and it transilluminates because it contains clear fluid. A hydrocele lies in the tunica vaginalis surrounding the front and sides of the testis, so the testis cannot be felt separately. One can get above both, unlike an inguinoscrotal hernia.
Scrotal swellings
- Separate from testis: epididymal cyst
- Surrounds testis: hydrocele
- Bag of worms: varicocele
- Cannot get above: hernia
Remember Above and behind, separate from the testis: epididymis.
Exam trap Any solid swelling of the testis itself needs ultrasound to exclude a tumour.
Why the other options are wrong
- Hydrocele Surrounds the testis, which cannot be felt separately.
- Varicocele Feels like a bag of worms and does not transilluminate.
- Indirect inguinal hernia One cannot get above it.
- Testicular tumour Arises in the testis and does not transilluminate.
A testicular tumour is removed through a scrotal incision instead of the inguinal route. Which additional lymph nodes are now at risk of metastasis?
Answer: Inguinal nodes as well as para-aortic
The testis develops on the posterior abdominal wall and descends, taking its lymphatics with it along the testicular vessels, so it drains to the para-aortic nodes at L1–L2. The scrotal skin drains like the perineum to the superficial inguinal nodes. Cutting through the scrotum to remove a testicular tumour opens a new route for tumour spread into scrotal lymphatics and hence to the inguinal nodes. This is why radical orchidectomy is done through an inguinal incision, with early clamping of the cord.
Testis vs scrotum lymph
- Testis: para-aortic (L1–L2)
- Scrotum: superficial inguinal
- Scrotal incision opens inguinal route
- Orchidectomy: inguinal approach
Remember Never cut the scrotum for a testicular tumour.
Exam trap Inguinal nodes in testicular cancer suggest scrotal involvement or previous scrotal surgery.
Why the other options are wrong
- Internal iliac nodes only The testis does not drain mainly to internal iliac nodes.
- Mediastinal nodes before para-aortic Mediastinal spread is later, through the thoracic duct.
- Popliteal nodes Drain the lateral foot and leg.
- Axillary nodes Drain the upper limb and breast.
Where this sits in the CPSP syllabus
- Paper 1: Pelvis and perineum, Male genital organs: testis, epididymis, vas, scrotum
- Surgery & Allied, Paper 2: Pelvis and perineum, Male genital organs: testis, epididymis, vas, scrotum
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