Scrotum in Animals: Andrology, Functions, Blood and Nerve Supply

The scrotum is a bilobed sac/pouch (derived from the skin and fascia) and is the external part of the male reproductive system which encloses the testis. It is located between the thighs except in the case of the boar and tom cat.

In the boar and tom cat, it is located caudal to the thighs, caudal and ventral to the ischiatic arch.

The scrotum is externally composed of skin which is relatively devoid of hair except in the ram (male sheep), buck (male goat), and tom cat (male cat).

Beneath the skin is the dartos muscle, which consists of fibroelastic tissue and unstriped muscle. The dartos muscle divides the scrotum into two halves.

It is closely attached to the tunica vaginalis and scrotal ligament, which is a remnant of the gubernaculum. The scrotal ligament is absent in bulls.

The testis and epididymis are fixed in the scrotum by means of the scrotal ligament, which is attached near the tail of the epididymis and mesorchium.

The scrotum has the following eight layers from the outside:

• Epidermis (outermost layer)
• Dermis
• Dartos muscle
• Connective tissue
• Parietal layer of vaginal process (PVP)
• Cavity of vaginal process (CV)
• Visceral layer of vaginal process (VVP)
• Tunica albuginea

The tunica albuginea penetrates the testicular parenchyma to join at the mediastinum. These fibrous septa divide the testicular parenchyma into lobules. The lobules contain highly coiled seminiferous tubules. About 75% of the testicular mass is composed of seminiferous tubules.

The scrotum, cremaster muscle, and pampiniform plexus maintain the testicular temperature.

Functions

• It encloses the male gonad.
• It provides suspensory attachment of testes with remaining animal body.
• It protects the testes from adverse stress conditions.
• It serves as a thermic chest of male gonad.
• It maintains gonadal temperature through thermoregulatory mechanism for optimum spermatogenesis.

The scrotum becomes flaccid and elongated due to the relaxation of the dartos and cremaster muscles in a hot climate. It becomes contracted and wrinkled in a cold climate.

Blood Supply

The external pudendal artery and also the internal pudendal artery in boars and cats.

Nerve Supply

• The genital nerve, which is a branch of the genitofemoral nerve arising from the second to fourth lumbar nerves and the perineal nerve.”
• The smooth muscle of the scrotum is supplied by the spermatic plexus from the pelvic plexus.