Overview

The scrotal skin is thin, rugose, pigmented and sparsely hairy, with many sweat and sebaceous glands; a midline raphe marks the line of fusion of the embryonic labioscrotal swellings. Beneath it lies the dartos fascia — a layer of smooth muscle fibres within superficial fascia that contains no fat. Dartos is continuous with the membranous layer of the superficial perineal fascia (Colles fascia) and with the membranous layer of the abdominal wall (Scarpa fascia), and forms the scrotal septum.

Temperature regulation is the scrotum's key function. In the cold, dartos contraction wrinkles the skin (reducing surface area) and the cremaster lifts the testes towards the body; in warmth both relax, and sweating cools the skin. The coverings of the testis beneath the dartos are the external spermatic fascia, cremasteric muscle and fascia, internal spermatic fascia and tunica vaginalis.

Location: Below the root of the penis and anterior to the perineum, hanging from the pubic region.

Anatomy

Innervation: Anterior: ilioinguinal nerve and genital branch of the genitofemoral nerve (L1). Posterior: posterior scrotal branches of the perineal nerve (pudendal, S2–S4) and the perineal branch of the posterior femoral cutaneous nerve (S2–S3). Dartos: sympathetic fibres.
Arterial supply: Anterior scrotal arteries (from the external pudendal arteries, branches of the femoral artery), posterior scrotal arteries (from the internal pudendal artery), and the cremasteric arteries.
Venous drainage: Anterior scrotal veins → external pudendal veins → great saphenous vein; posterior scrotal veins → internal pudendal veins.
Lymphatic drainage: Superficial inguinal nodes (unlike the testis, which drains to para-aortic nodes).
Development: Labioscrotal swellings, fused in the midline under DHT; homologous to the labia majora.

Function

Houses and protects the testes.
Keeps the testes ≈2–3 °C below core temperature.

Clinical significance

Scrotal swellings

If you cannot get above the swelling it is an inguinoscrotal hernia; if it transilluminates and the testis is impalpable within it, it is a hydrocele; separate cystic swellings above the testis are epididymal cysts. A firm, non-tender mass in the testis is cancer until proven otherwise.

Fournier gangrene

Rapidly spreading polymicrobial necrotising fasciitis of the scrotum and perineum, usually in diabetic or immunocompromised men; requires urgent debridement.

Extravasation of urine

Rupture of the spongy urethra lets urine track into the superficial perineal pouch, distending the scrotum, penis and lower abdominal wall but not the thighs (Colles fascia fuses with the fascia lata).

Compiled from standard anatomy and physiology references — see the Reproductive System sources. For education only; not medical advice.