Diagram of the scrotum. On the left side, the cavity of the tunica vaginalis has been opened; on the right side, only the layers superficial to the cremaster muscle have been removed.
In regard to humans, the scrotum is a suspended two-chambered sac ofskin andmuscular tissue containing the testicles and the lower part of thespermatic cords. It is located behind thepenis and above theperineum. Theperineal raphe is a small, vertical ridge of skin that expands from theanus and runs through the middle of the scrotum front to back. The scrotum is also a distention of the perineum and carries some abdominal tissues into its cavity including thetesticular artery,testicular vein, andpampiniform plexus.
The skin on the scrotum is more highly pigmented in comparison to the rest of the body. Theseptum is a connective tissue membrane dividing the scrotum into two cavities.[6]
The scrotal lymph initially drains into the superficial inguinal lymph nodes, this then drains into the deep inguinal lymph nodes. The deep inguinal lymph nodes channel into the common iliac, which ultimately releases lymph into the cisterna chyli.
One testis is typically lower than the other, which is believed to function to avoid compression in the event of impact; in humans, the left testis is typically lower than the right.[8] An alternative view is that testis descent asymmetry evolved to enable more effective cooling of the testicles.[9]
Development of external genitals showinghomologues fromindifferent to both sexes - male on left
During the fifth week after fertilization, thegenital 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 thelabioscrotal folds into the scrotum. Thescrotal raphe is formed when the embryonic, urethral groove closes by week 12.[10]
Though the testes and scrotum form early in embryonic life, sexual maturation begins upon enteringpuberty. The increased secretion of testosterone causes the darkening of the skin and development ofpubic hair on the scrotum.[11]
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 affectspermatogenesis.[12] Temperature control is accomplished by thesmooth 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 thecremaster muscle in the abdomen and thedartos fascia (muscular tissue under the skin that makes the scrotum appear wrinkly).[11]
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.[12] 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.[14] The scrotum is also considered to be anerogenous zone.[15]
Common slang terms for the scrotum areballsack,nutsack, andteabag.
Some men will get apiercing on the skin of the scrotum, any of which is called ahafada (e.g., scrotal ladder). Side-to-side or front-to-back piercings that pass through the scrotum are known astransscrotal piercings.
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 assack 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.[16]
Unlikeplacentals, some malemarsupials have a scrotum that is anterior to the penis,[19][20][21][22] which is not homologous to the scrotum of placentals,[23] although there are several marsupial species without an external scrotum.[24]
"Gross Anatomy Image". Medical Gross Anatomy Atlas Images. University of Michigan Medical School. 1997. Archived fromthe original on 2016-08-19. Retrieved2015-02-23.
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