Scrotum

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For the obsolete dinosaur fossil name, see Megalosaurus#"Scrotum humanum".
Scrotum
Scrotum warm-cold.jpg
Human scrotum (both relaxed and tense states)
Latin Scrotum
Gray's p.1237
Artery Anterior scrotal artery & Posterior scrotal artery
Vein Testicular vein
Nerve Posterior scrotal nerves, Anterior scrotal nerves, genital branch of genitofemoral nerve, perineal branches of posterior femoral cutaneous nerve
Lymph Superficial inguinal lymph nodes
Precursor labioscrotal folds
MeSH Scrotum

The scrotum is a dual-chambered protuberance of skin and muscle, present in some male mammals, that contains the testicles and is divided by a septum.[1] It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the scrotum becomes covered with pubic hair at puberty.

The scrotum is biologically homologous to the labia majora in females.

Structure[edit]

Innervation[edit]

Nerve Surface[2]
Genital branch of genitofemoral nerve anterolateral
Anterior scrotal nerves (from ilioinguinal nerve) anterior
Posterior scrotal nerves (from perineal nerve) posterior
perineal branches of posterior femoral cutaneous nerve inferior

Function[edit]

Image showing musculature and inner workings of the scrotum.

The function of the scrotum is to keep the temperature of the testes slightly lower than that of the rest of the body.[3] For human beings, the scrotum temperature should be about 35-36 degrees Celsius (95-96.8 degrees Fahrenheit), i.e. one to two degrees Celsius below the accepted normal body temperature of 37 degrees Celsius (98.6 degrees Fahrenheit). Higher temperatures may be damaging to sperm count. The temperature is controlled by the scrotum moving the testicles closer to the abdomen when the ambient temperature is cold, and farther away when it is hot. Moving the testes away from the abdomen and increasing the exposed surface area allow a faster dispersion of excess heat. This is done by means of contraction and relaxation of the cremaster muscle in the abdomen and the dartos fascia (muscular tissue under the skin) in the scrotum.


However, this may not be the main function of the scrotum. The volume of sperm produced by the testes is small (0.1-0.2 ml).[clarification needed] It has been suggested that if testes were situated within the abdominal cavity that they would be subjected to the regular changes in abdominal pressure that are exerted by the abdominal muscles. This squeezing and relaxing would result in the more rapid emptying of the testes and epididymis of sperm before the spermatozoa were matured sufficiently for fertilization. Some mammals — elephants and marine mammals, for example – do keep their testes within the abdomen and there may be mechanisms to prevent this inadvertent emptying.

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.

Contraction of the abdominal muscles, and changes in intra-abdominal pressure, can often lift and lower the testicles within the scrotum. Contraction of the muscle fibers of the dartos tunic (or fascia) is completely involuntary and results in the appearance of increased wrinkling and thickening of the scrotal skin. The testicles are not directly attached to the skin of the scrotum, so this dartos contraction results in their sliding toward the abdomen. They also, in some men, can be lifted the same way by tightening the anus and pelvic muscles, doing Kegel exercises.

Although the ideal temperature for sperm growth varies between species, it usually appears, in warm-blooded species, to be a bit cooler than internal body temperature, making the scrotum necessary. Since this leaves the testicles vulnerable in many species, there is some debate on the evolutionary advantage of such a system. One theory is that the impregnation of females who are ill is less likely when sperm is highly sensitive to elevated body temperatures. An alternative explanation is to protect the testes from jolts and compressions associated with an active lifestyle. Animals that have stately movements – such as elephants, whales, and marsupial moles – have internal testes and no scrotum.[4]

Clinical significance[edit]

A study has indicated that use of a laptop computer positioned on the lap can negatively affect sperm production.[5][6]

A common problem of the scrotum is the development of masses. Common scrotal masses may have any of a variety of causes, including a sebaceous cyst, also called an epidermal cyst; a hydrocele, a hematocele, a spermatocele or a varicocele.

Another condition is blisters caused by chafing or scratching of the scrotum while it is damp. This condition is often seen in males undergoing puberty, as emerging pubic hairs cause an itch and an urge to scratch. Powdering the scrotum to absorb moisture can help to prevent this discomfort. Contact dermatitis may cause redness, burning, swelling, and itching of the entire scrotum. It can result from soaps, solvents, detergents, and natural irritants such as poison ivy. Inguinal hernia and yeast infection may occur, and there may be swelling resulting from conditions external to the scrotum, including heart failure, kidney or liver disease, cherry angioma and testicular torsion.

Skin conditions which have not been successfully identified may be referred to as non-specific scrotal dermatitis.

See also[edit]

This article uses anatomical terminology; for an overview, see anatomical terminology.

References[edit]

  1. ^ "Scrotum". National Institutes of Health. Retrieved 6 January 2011. 
  2. ^ Moore, Keith; Anne Agur (2007). Essential Clinical Anatomy, Third Edition. Lippincott Williams & Wilkins. p. 132. ISBN 0-7817-6274-X. 
  3. ^ "About the Male Reproductive System". KidsHealth. Retrieved 6 January 2011. 
  4. ^ "Science : Bumpy lifestyle led to external testes - 17 August 1996 - New Scientist". Retrieved 2007-11-06. 
  5. ^ "Laptops may damage male fertility". BBC News. 2004-12-09. Retrieved 2012-01-30. 
  6. ^ Sheynkin, Yefim; et al. (February 2005). "Increase in scrotal temperature in laptop computer users". Hum. Reprod. 20 (2): 452–455. doi:10.1093/humrep/deh61 (inactive 2014-05-22). PMID 15591087. 

Additional images[edit]