How does scrotum regulates the temperature of testes?

There are three mechanisms for regulating the temperature of the testes:

This is a subcutaneous layer of smooth muscle.
When scrotum is exposed to cold temperature, this muscle contracts.
This makes the scrotum tight and wrinkled.
This action holds the testes closely against the warm body and reduces the surface area of the scrotum, thus reducing the heat loss.

This is an extension of the internal oblique muscle that descends through the spermatic cord.
When the scrotum is exposed to cold temperatures, cremaster muscle contracts and draws testes closer to the body to keep them warm.
On the contrary, when scrotum is exposed to warm or high temperature, cremaster muscle relaxes and the testes are drawn farther from the body.

This is an extensive network of veins from the testes.
These veins surround the testicular artery in the spermatic cord.
The plexus prevents warm arterial blood from overheating the testis,which would inhibit sperm production.
It acts as a countercurrent heat exchanger.
Blood ascending the testes is relatively cool, about 35℃ and absorbs heat from the warmer blood, about 37℃ descending through the testicular artery.
By the time the arterial blood reaches the testis, it is 1.5 to 2.5 degrees cooler than it was when it left the pelvic cavity.

Other articles:
Scrotum FAQ

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