The dartos is a smooth muscle layer (not skeletal muscle) in the superficial scrotal fascia, innervated by sympathetic fibres rather than somatic motor nerves. Its contraction during cold exposure thickens and wrinkles the scrotal skin, reducing surface area to conserve heat. In warm conditions it relaxes, allowing the scrotum to become smooth and pendulous with increased surface area for heat dissipation.
| Origin | Subcutaneous tissue of the scrotum — no bony origin |
|---|---|
| Insertion | Scrotal skin — inserts directly into the overlying scrotal skin layers |
| Nerve Supply | Sympathetic fibres from the genitofemoral nerve |
| Blood Supply | Perineal artery |
| Actions | Wrinkling and thickening of the scrotal skin during cold; Creates the rugose scrotal surface that increases or decreases surface area for temperature regulation |
|---|
Working in concert with the cremaster (skeletal muscle, elevating the testis) and the dartos (smooth muscle, wrinkling the scrotum), temperature regulation maintains the scrotal testicular environment 2 to 3 degrees below core body temperature required for optimal spermatogenesis.
The dartos fascia is the surgical layer used for two-layer testicular prosthesis fixation and for orchidopexy suturing in testicular torsion surgery. Absence of the scrotal dartos rugate response to cold is a sign of perineal nerve denervation or severe scrotal pathology. The dartos can be used as a vascular flap for hypospadias repair — the dartos pedicled flap based on the perineal vasculature provides coverage for urethral reconstruction.
The dartos response is directly observable — the scrotal skin rugosity increases (dartos contracts) when cold stimulus is applied to the scrotum, and the skin smooths (dartos relaxes) during warmth.
Pedicled dartos fascia flap used to provide vascularised coverage over urethroplasty in hypospadias repair, reducing fistula formation.
