Scrotum

Development

During the fifth week after fertilization, the genital ridge grows behind the peritoneal membrane. By the sixth week, string-like tissues called primary sex cords form within the enlarging genital ridge. Externally, a swelling called the genital tubercule appears over the cloacal membrane.

Testosterone secretion starts during week eight, reaches peak levels during week 13 and eventually declines to very low levels by the end of the second trimester. The testosterone causes the masculinization of the labioscrotal folds into the scrotum. The scrotal raphe is formed when the embryonic, urethral groove closes by week 12.

Scrotal growth and puberty

Though the testes and scrotum form early in embryonic life, sexual maturation begins upon entering puberty. The increased secretion of testosterone causes the darkening of the skin and development of pubic hair on the scrotum.

Function

The scrotum regulates the temperature of the testicles and maintains it at 35 degrees Celsius (95 degrees Fahrenheit), i.e. two or three degrees below the body temperature of 37 degrees Celsius (99 degrees Fahrenheit). Higher temperatures affect spermatogenesis. Temperature control is accomplished by the smooth muscles of the scrotum moving the testicles either closer to or further away from the abdomen dependent upon the ambient temperature. This is accomplished by the cremaster muscle in the abdomen and the dartos fascia (muscular tissue under the skin that makes the scrotum appear wrinkly).

During sexual arousal, the scrotum will also tighten and thicken in the course of penile erection.

Having the scrotum and testicles situated outside the abdominal cavity may provide additional advantages. The external scrotum is not affected by abdominal pressure. This may prevent the emptying of the testes before the sperm were matured sufficiently for fertilization. Another advantage is it protects the testes from jolts and compressions associated with an active lifestyle. The scrotum may provide some friction during intercourse, helping to enhance the activity. The scrotum is also considered to be an erogenous zone.

Society and culture

Common slang terms for the scrotum are ballsack, nutsack, and teabag.

Some men will get a piercing on the skin of the scrotum, any of which is called a hafada (e.g., scrotal ladder). Side-to-side or front-to-back piercings that pass through the scrotum are known as transscrotal piercings.

Scrotoplasty is a sex reassignment surgery that creates a scrotum for trans men using tissue from the labia majora, or a plastic surgery that repairs or reconstructs the scrotum.

Cock and ball torture is a kink that may involve bringing pain to the scrotum. Beyond kink, a person (especially a man) may hit someone in the testicles as a gendered cultural practice known as sack tapping. This phenomenon is complex and contains many (often conflicting) meanings: it is used to both strengthen inclusive bonds and reinforce exclusive hierarchies, it is both humorous and violent, and both juvenile and present in male-dominated social spheres beyond those of adolescence.

Other animals

A scrotum is a synapomorphy of boreoeutherians. The anus is separated from the scrotum by the perineum in these mammals. The testicles remain in the body cavity in all other vertebrates, including both the cloacal animals.

It has been secondarially lost in hippopotamuses, rhinoceroses, hedgehogs, moles, pangolins, tapirs, numerous families of bats and rodents, the whales and dolphins, and seals.

Some male marsupials have a scrotum that is anterior to the penis, which is not homologous to the scrotum of placentals, although there are several marsupial species without an external scrotum.

Clinical significance

Diseases and conditions

The scrotum and its contents can develop many diseases and can incur injuries. These include:

• Candidiasis (yeast infection)
• Sebaceous cyst
• Epidermal cyst
• Hydrocele testis
• Hematocele
• Molluscum contagiosum
• Spermatocele
• Paget's disease of the scrotum
• Varicocele - enlargement of the pampiniform venous complex
• Inguinal hernia
• Epididymo-orchitis
• Testicular torsion
• Pruritus scroti - irritation of the scrotum (itchiness)
• Genital warts - sexually transmitted infection
• Testicular cancer
• Dermatitis
• Undescended testes (also known as cryptorchidism)
• Chyloderma - swollen scrotum caused by a lymphatic obstruction
• Mumps
• Scabies
• Herpes - sexually transmitted infection
• Pubic lice
• Chancroid (Haemophilus ducreyi) - sexually transmitted infection
• Chlamydia (Chlamydia trachomatis) - sexually transmitted infection
• Gonorrhea (Neisseria gonorrhoeae) - sexually transmitted infection
• Granuloma inguinale or (Klebsiella granulomatis)
• Syphilis (Treponema pallidum) - sexually transmitted infection
• Scrotal eczema
• Polyorchidism - the presence of three or more testicles
• Scrotal psoriasis disease
• Riboflavin deficiency
• Chimney sweeps' carcinoma (scrotal cancer)