(Image source: Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/)
The scrotum is a feature of the male reproductive system that hangs from the body at the front of the pelvis, between the legs. It is a sac of skin divided into two chambers, and it sits next to the upper thighs. The two compartments of the scrotum are distinguished externally by a middle ridge called the raphe. Internally, the raphe connects to a muscular partition, the septum, which serves to divide the scrotum into its two areas.
The scrotum is continuous with the skin of the lower abdomen and is located directly behind the penis and in front of the anus. It is found on most land-based mammals, and is biologically homologous to the labia majora in females. It is a multi-layered structure that houses key components of the male reproductive system, including:
The scrotum regulates the temperature of the testes and maintains it at a few degrees below the body temperature as higher temperatures can negatively affect spermatogenesis. (The relatively cool temperature of the scrotum is believed to be important for the production of healthy sperm). Temperature control is accomplished by the muscles of the scrotum moving the testicles either closer to or further away from the abdomen dependent upon the ambient temperature.
In humans and some other mammals the scrotum becomes covered with pubic hair at puberty. The scrotum will usually tighten during penile erection and when exposed to cold temperatures. One testis is typically lower than the other to avoid compression in the event of an impact.
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Anus - the opening at the end of the alimentary canal through which solid waste matter leaves the body.
Ductus deferens - ducts that transport sperm from the epididymis to the ejaculatory ducts.
Epididymis - a tube that connects a testicle to a ductus deferens in the male reproductive system.
External spermatic fascia - a bilayered covering of the testis derived from abdominal muscle.
Homologous - having the same relation, relative position, or structure.
Labia majora - the larger outer folds of the vulva.
Puberty - the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction.
Pubic hair - body hair that is found in the genital area of adolescent and adult humans.
Testes - male reproductive glands, homologous to the female ovary, whose functions are to produce both sperm and androgens, primarily testosterone.
Vulva - the name for the female external genitalia including the clitoris, labia (vaginal lips) and the opening to the vagina.
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"Scrotum". National Institutes of Health. Retrieved 6 January 2011.
Moore, Keith; Anne Agur (2007). Essential Clinical Anatomy, Third Edition. Lippincott Williams & Wilkins. p. 132. ISBN 978-0-7817-6274-8.
"Scrotum". Encyclopædia Britannica. Retrieved 2015-02-24.
Libbie Henrietta Hyman (15 September 1992). Hyman's Comparative Vertebrate Anatomy. University of Chicago Press. pp. 583–. ISBN 978-0-226-87013-7.
Jones, Richard (2013). Human Reproductive Biology. Academic Press. p. 74. ISBN 9780123821850.
"VIII. The Lymphatic System. 5. The Lymphatics of the Lower Extremity. Gray, Henry. 1918. Anatomy of the Human Body". Retrieved 2015-02-24.
"Science : Bumpy lifestyle led to external testes - 17 August 1996 - New Scientist". New Scientist. Retrieved 2007-11-06.
William F. Perrin; Bernd Würsig; J.G.M. Thewissen (26 February 2009). Encyclopedia of Marine Mammals. Academic Press. ISBN 978-0-08-091993-5.
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