AN46.1-5 | Male external genitalia — Gate Quiz

Correct! The testis develops retroperitoneally near L1–L2 (beside the developing kidney) and descends into the scrotum guided by the gubernaculum, dragging its blood supply (from the aorta at L2), venous drainage, lymphatics, and nerve supply. This is why testicular vessels all originate from abdominal structures.

Embryological descent from L1–L2 explains: testicular artery from aorta at L2, venous drainage to IVC/renal vein, nerve supply T10 (periumbilical referred pain), and lymphatics to para-aortic nodes at L2.

Incorrect. The testis develops near L2 in the fetus. During descent, it carries its aortic blood supply, renal vein venous drainage, and T10 nerve supply. Understanding descent explains all testicular applied anatomy.

Correct! The cremasteric reflex requires intact afferent (ilioinguinal/femoral branch of genitofemoral) + efferent (genital branch of genitofemoral → cremaster) pathways. Torsion twists the spermatic cord, mechanically disrupting the cremasteric fibres and their neurovascular supply, abolishing the reflex.

Absent cremasteric reflex in acute scrotal pain = testicular torsion until proven otherwise. The twist mechanically disrupts the reflex arc. Cremasteric reflex preserved = epididymo-orchitis (inflammation, not mechanical disruption).

Incorrect. Torsion twists the entire spermatic cord, disrupting the cremasteric muscle and its nerve supply within the cord. The genital branch of the genitofemoral nerve (the efferent limb) is interrupted by the twist → reflex arc broken.

Correct! Testicular lymphatics drain to para-aortic (lumbar) nodes at L2, reflecting the gonadal origin near L2 in the fetus. Inguinal nodes are NOT involved unless the tumour has spread to the scrotal skin. CT staging must focus on the retroperitoneal nodes at the L2 level.

Testicular cancer staging: look for para-aortic nodes at L2. A patient with large retroperitoneal nodes but no inguinal nodes is NOT understaged. The distinction saves patients from incorrect staging and inappropriate surgery.

Incorrect. Testis → para-aortic nodes at L2. Scrotal skin → inguinal nodes. Testicular cancer staging CT focuses on retroperitoneal lymph nodes from L2 downward. Inguinal nodes are only involved in advanced scrotal skin invasion.

Correct! Left testicular vein → left renal vein (right-angle junction, ~10 cm longer column, higher hydrostatic pressure) vs right testicular vein → IVC (oblique angle, lower resistance). The anatomical right-angle junction increases resistance to venous drainage on the left → valve incompetence → retrograde flow → pampiniform plexus dilatation.

Left varicocele: left testicular vein → left renal vein (right angle) = high resistance. Right: right testicular vein → IVC (oblique) = low resistance. New left varicocele in an older man = renal vein obstruction (renal cell carcinoma) until proven otherwise.

Incorrect. The key anatomical factor is the right-angle drainage of the left testicular vein into the left renal vein (compared to the oblique right-side drainage into the IVC). This creates greater resistance on the left → valves fail → varicocele.

Correct! In paraphimosis, the retracted foreskin forms a tight constricting ring at the coronal sulcus that obstructs venous and lymphatic return from the glans. Progressive oedema makes the glans larger → harder to reduce → a vicious cycle. If untreated, eventually arterial compromise can occur. Treatment: manual reduction (ice + pressure) or emergency dorsal slit.

Paraphimosis = urological emergency. Tight preputial ring → venous/lymphatic obstruction → glans oedema → irreducible → progressive constriction. Treatment: manual reduction (squeeze glans firmly to reduce oedema, then reduce foreskin) or dorsal slit under local anaesthesia.

Incorrect. The primary mechanism is venous and lymphatic obstruction → progressive oedema of the glans → the swollen glans cannot be reduced under the ring → escalating constriction. Arterial compromise is a late, secondary effect.

Correct! The corpus spongiosum is the single ventral erectile body that: (1) surrounds the penile urethra throughout its penile course; (2) expands distally to form the glans penis (covering the distal ends of both corpora cavernosa); (3) expands proximally as the bulb of the penis (attached to the perineal membrane).

Three erectile bodies: 2 corpora cavernosa (dorsal, paired, main erectile bodies) + 1 corpus spongiosum (ventral, single, contains urethra, forms glans distally, forms bulb proximally).

Incorrect. The corpus spongiosum is the erectile body that contains the urethra and forms the glans. The two corpora cavernosa lie dorsally and end just before the glans (they are capped by the glans). The bulb is the proximal expansion of the corpus spongiosum.

Correct! The pelvic splanchnic nerves (nervi erigentes) arise from S2, S3, S4 and carry parasympathetic fibres to the helicine arteries of the corpora cavernosa. Parasympathetic stimulation → vasodilation → blood fills cavernous spaces → veno-occlusion → erection. This is why spinal cord injuries below T6 often spare erection (sacral parasympathetics intact).

Erection: parasympathetic S2,3,4 → pelvic splanchnic nerves → helicine arteries dilate → cavernosal filling → veno-occlusion. Ejaculation: sympathetic L1,2 → hypogastric nerve → smooth muscle contraction.

Incorrect. Penile erection = parasympathetic (S2,3,4) via pelvic splanchnic nerves. Ejaculation = sympathetic (L1,L2) via hypogastric nerve. Mnemonic: "Point and Shoot" — Parasympathetic = Point (erection, S2,3,4); Sympathetic = Shoot (ejaculation, L1,L2).

Correct! Spermatozoa leaving the seminiferous tubules are morphologically complete but physiologically immature — they cannot swim and cannot fertilise an oocyte. During 12 days of transit through the ~7-metre coiled epididymis, they acquire forward motility and fertilisation capacity through biochemical changes in the epididymal fluid.

Epididymis functions: (1) sperm maturation — gains motility and fertilisation capacity over 12 days; (2) storage of mature sperm in the tail (cauda); (3) fluid reabsorption from rete testis. Obstruction of the epididymis (post-infection) → obstructive azoospermia → infertility.

Incorrect. Spermatozoa leave the testis immotile. The 12-day epididymal transit (head → body → tail) achieves sperm maturation — the ability to swim progressively and to fertilise an egg. Testosterone is produced by the Leydig cells of the testis, not the epididymis.

Correct! The testicular nerve supply is via the testicular plexus at T10 — reflecting the gonadal origin near L1–L2 in the fetus (the T10 segment of the spinal cord corresponds to the periumbilical region). Visceral pain from testicular inflammation, torsion, or trauma is referred to the periumbilical T10 dermatome, not to the scrotum (which is L1).

Testicular nerve supply T10 → periumbilical referred pain. Appendix is also T10 → early appendicitis also periumbilical. Both testicular torsion and early appendicitis can present with periumbilical pain — history and examination distinguish them.

Incorrect. The testis is innervated via the testicular plexus (T10). Visceral pain is referred to the T10 dermatome = periumbilical. The scrotum is innervated by L1 (ilioinguinal nerve) — somatic scrotal pain is in the L1 distribution. Testicular torsion causes periumbilical pain + scrotal pain.

Correct! The dorsal nerve of the penis (S2,3) — a branch of the pudendal nerve — is the primary sensory supply to the glans and foreskin. A penile ring block infiltrates local anaesthetic circumferentially at the base of the penis (at 10 and 2 o'clock positions dorsally + ventral infiltration at Buck's fascia level) to block the dorsal nerves bilaterally and the deep branches.

Dorsal nerve of penis (S2,3) = sensory to glans and foreskin. Penile ring block: infiltrate at 10 and 2 o'clock dorsally (Buck's fascia level) + ventral midline (to catch ventral branches). This is the standard technique for painless circumcision under local anaesthesia.

Incorrect. The dorsal nerve of the penis (branch of pudendal nerve, S2,3) is the primary sensory nerve for the glans and foreskin — the structures operated on during circumcision. Penile ring block infiltrates at the base targeting these dorsal nerves.