Cremaster muscle

Cremaster muscle
The cremaster muscle appears as a thin layer just superficial to the tunica vaginalis.
Latin	musculus cremaster
Gray's	subject #118 414
Origin	inguinal ligament
Insertion
Artery	Cremasteric artery
Nerve	genital branch of genitofemoral nerve
Actions	raise and lower the scrotum

The cremaster muscle is a muscle that covers the testis.

Contraction

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.

Clinically, a reflex arc termed the cremasteric reflex 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 boys than in men.

The cremaster can also be contracted voluntarily, by contracting the pubococcygeus muscle (using Kegels), or by sucking in the abdomen.

Development and sex differences

The cremaster develops to its full extent only in males; in females it is represented by only a few muscle loops.

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

In rats, it has been shown that cremaster muscles developed from the gubernacular bulb.

Structure

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.

Innervation and vascular supply

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.

Etymology

The word is derived from the Greek verb κρεμάννυμι = "I hang (transitive)", not from Latin cremare.

Additional images

The scrotum.

The right testis, exposed by laying open the tunica vaginalis.

External links

• -731185075 at GPnotebook
• LUC crem
• SUNY Labs 36:07-0102 - "Inguinal Region, Scrotum and Testes: Layers of the Spermatic Cord"
• Cremaster+muscle at eMedicine Dictionary