scrotum

scrotum To quote a 1940s edition of Gray's anatomy: ‘The scrotum forms an admirable covering for the protection of the testes. These bodies, lying suspended and loose in the cavity of the scrotum … are capable of great mobility, and can therefore easily slip about within the scrotum, and thus avoid injuries from blows or squeezes.’ Indeed so. Modern anatomical texts have lost a certain poetry.

The skin of the scrotum is exceptionally thin and ‘beset with thinly scattered, crisp hairs …’ but the whole pouch is thickened by an underlying sheet of involuntary muscle (dartos), closely linked to the skin, and responsible for its corrugated appearance. This muscle layer is continuous with a septum, which divides the scrotum into compartments for the two testes and their spermatic cords; it is ‘separated from the subjacent parts by delicate areolar tissue upon which it glides with the greatest facility’. These subjacent parts are a fibrous capsule, and then a serous (fluid-secreting) membrane, which slides upon (and is continuous with) a membrane covering the testis. These membranes form a closed, fluid-lined sac, like a deflated balloon, that sometimes swells up to become a hydrocele. The cremaster muscle links the lowest part of the abdominal wall above the groin to these coverings of the testis, and can retract it upwards: this occurs reflexly when the inner thigh is stroked.

The contents of the scrotum have descended into it, usually before birth, from the abdominal cavity. The route was through the inguinal canal at the groin. Each testis dragged after it a string of elongating vessels and nerves and the vas deferens; these constitute the spermatic cords. Each cord maintains its connection with the abdominal cavity via the canal, whence the vas joins the urinary tract below the bladder. Because the inguinal canal breaches the muscular and fibrous integrity of the abdominal wall, it can become further weakened and expanded, allowing abdominal contents to extrude through it as an inguinal hernia. A large hernia can extend right down into the scrotum.

In the early weeks of fetal life, before gender differences are apparent, there is a labioscrotal swelling on each side; these swellings join up to develop into the scrotum when maleness is genetically ordained.

Sheila Jennett

See also genitalia; testes.