Cremaster muscle

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Cremaster muscle

The cremaster muscle appears as a thin layer just superficial to the tunica vaginalis.
Gray's	subject #118
Origin:
Insertion:
Blood:	Cremasteric artery
Nerve:	genital branch of genitofemoral nerve
Action:

The cremaster muscle is a muscle that 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, the lateral cremaster muscle originates from the internal oblique muscle, just superior to the inguinal canal, and the middle of the inguinal ligament. The medial cremaster muscle, which sometimes is absent, originates from the pubic tubercle and sometimes the lateral pubic crest. Both insert into the tunica vaginalis underneath the testis.

In human females, the cremaster muscle is smaller and is found on the round ligament.

The cremaster muscle is innervated from the genital branch of the genitofemoral nerve and supplied by the cremasteric artery. It receives distinctly different innervation and vascular supply in comparison to the internal oblique. In rats, it has been shown that cremaster muscles developed from the gubernacular bulb.

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. Not all males are capable of doing this, as it requires pelvic muscle strength.