Cremaster muscle: Encyclopedia - Cremaster muscle

Cremaster muscle

The cremaster muscle is a muscle which covers the testis. Its function is to raise and lower the scrotum in order to regulate the temperature of the testis and promote spermatogenesis. In a cool environment the cremaster draws the testis closer to the body preventing heat loss, while when it is warmer the cremaster relaxes allowing the testis to cool. The cremaster develops to its full extent only in males; in females it is represented by only a few muscle loops.

In human males, the cremaster muscle is a thin layer of skeletal muscle found in the inguinal canal and scrotum between the external and internal layers of spermatic fascia, surrounding the testis and spermatic cord. The cremaster muscle is a paired structure, there being one on each side of the body. Anatomically, it is an extension of the internal oblique muscle and originates from the fibers of this muscle just superior to the inguinal canal. It receives its innervation from the genital branch of the genitofemoral nerve.

Clinically, a reflex arc can be demonstrated by lightly stroking the skin of the inner thigh downwards from the hip towards the knee. This causes the cremaster muscle on the same side to rapidly contract, raising that testicle. This so called cremasteric reflex is much more pronounced in children than in adults.

The cremaster can also be contracted voluntarily, by contracting the PC muscle (using Kegels), or by sucking in the abdomen. This doesn't happen in all males, however: the stronger the pelvic muscles, the easier it is to cause the cremaster to contract.

Adapted from the Wikipedia article "Cremaster muscle", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki