In males, the cremaster muscle raises and lowers the testes to try to keep sperm at the ideal temperature, according to Healthline. When a male enters a cold environment, the cremaster muscle draws the testes in closer to the body. If the testes get too warm, the muscle pushes the organs farther away from the body.
Healthline indicates the cremaster muscle responds to the "fight or flight" reflex. If a man is scared, the testes get pulled closer to the body. This is so the body protects these organs. Contrarily, a nerve along the inner thigh causes the cremasteris reflex wherein the muscle raises the testes.
Dictionary.com reveals the cremaster muscle in females covers the round ligament of the uterus. In males, the muscle surrounds the spermatic cord in addition to the testes. Nerves in the muscle come from the main genitofemoral nerve.
The cremaster muscle covers the testes completely. An article in Anatomical Record explains that motor units responsible for the muscle's movement are very different from normal skeletal muscles. Smooth muscle fibers in the cremaster muscle are more widespread rather than arranged in layers. These fibers have extra nerve endings not seen in other muscles in the human body. Scientists believe these extra muscle fibers, along with many more nerves, enhance the motor units of the cremaster muscle.