26.3B: Scrotum
The purpose of the scrotum is to provide the testes with a chamber of appropriate temperature for optimal sperm production.
- Describe the functions of the scrotum
Key Points
- Moving the testes away from the abdomen and increasing the exposed surface area allow a faster dispersion of excess heat.
- If testes were in the abdomen, constant pressure from abdominal muscles would possibly empty the testes and epididymis before sperm were sufficiently mature for fertillization.
- The function of the scrotum appears to be to keep the temperature of the testes slightly lower than that of the rest of the body.
Key Terms
- scrotum : The bag of skin and muscle that contains the testes in mammals.
- testosterone : A steroid hormone that plays a key role in male reproductive development including the promotion of secondary sexual characteristics.
- epididymis : A narrow, tightly-coiled tube where sperm are stored during maturation. It connects the efferent ducts from the rear of each testicle to its vas deferens.
Anatomical Considerations
The scrotum is a dual-chambered suspended sack of skin and smooth muscle that contains the testes, and is homologous to the labia majora in females. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, increased testosterone secretion during puberty causes the darkening of the skin and development of pubic hair on the scrotum. The left testis is usually lower than the right, which may function to avoid compression in the event of impact. This asymmetry may also allow more effective cooling of the testes.
Function
The function of the scrotum appears to be to keep the temperature of the testes slightly lower than that of the rest of the body. For human beings, the temperature should be one or two degrees Celsius below body temperature (around 35 degrees Celsius or 95 degrees Fahrenheit); higher temperatures may be damaging to sperm count.
The temperature is controlled by scrotal movement of the testes away or towards the body depending on the environmental temperatures. 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 and the dartos fascia in the scrotum.
However, temperature regulation may not be the only function of the scrotum. It has been suggested that if testes were situated within the abdominal cavity, they would be subjected to the regular changes in abdominal pressure that are exerted by the abdominal muscles, resulting 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 where there may be mechanisms to prevent this inadvertent emptying.
The scrotum : Image of the external, muscle, and deep tissue views of the scrotum.