munasäkkiä

Munasäkkiä, also known as the scrotum, is an external pouch of skin that hangs below the penis in males. Its primary function is to regulate the temperature of the testes, which are housed within it. Sperm production is highly sensitive to temperature, and the scrotum's ability to contract and relax helps maintain an optimal temperature for this process, slightly cooler than the core body temperature.

The scrotum is composed of several layers, including skin, dartos muscle, and fascial layers. The dartos muscle allows the scrotum to wrinkle and contract, pulling the testes closer to the body for warmth or relaxing to allow them to hang lower when it's cooler. This muscle is involuntary, meaning it contracts and relaxes without conscious control.

During fetal development, the testes descend from the abdominal cavity through the inguinal canal into the scrotum. This descent is crucial for proper testicular function and fertility. The scrotum also provides a protective covering for the testes against physical injury. It is a vital component of the male reproductive system.