Cremaster muscle consists of loosely arranged muscle fasciculi covering the spermatic cord. It is a thin layer of skeletal muscle found in the inguinal canal and scrotum between the external and internal spermatic fasciae. It surrounds the spermatic cord and testis. There are two cremaster muscles, one on each side. The thickness is variable in different age groups, being thickest in young men. Sometimes it forms an incomplete coating around the spermatic cord, known as cremasteric fascia. This extends around the testis but lies within the external spermatic fascia.
Origin and Insertion of cremaster:
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.
The entire muscle appears to form continuous loops that pass from the middle of the inguinal ligament as far as the tunica vaginalis, and then return to attach to the pubic tubercle.
Blood supply of cremaster:
Cremaster muscle receives its vascular supply from the cremasteric artery, a branch of the inferior epigastric artery.
Nerve supply to cremaster:
Cremaster muscle receives its nerve supply from the genital branch of genitofemoral nerve. The root of this nerve is L1 and L2 (first and second lumbar spinal nerves).
Actions of cremaster:
Cremaster pulls the testis up towards the superficial inguinal ring. Although its fibers are striated, it is not usually under voluntary control. Stroking the skin of the medial side of the thigh evokes a reflex contraction of the muscle, the cremasteric reflex, which is most pronounced in children. It may represent a protective reflex, and the cremaster may also have a role in testicular thermoregulation.