Cremaster Muscle And Fascia
The cremaster muscle is a thin muscle that covers the testis and the spermatic cord. Contraction Its function is to raise and lower the testes in order to regulate the temperature of the testes and promote spermatogenesis. Contraction may also occur during arousal which can prevent injury to the testicles during sex. In a cool environment, the cremaster draws the testis closer to the body and reduces surface area, thereby reducing heat loss, while when it is warmer, the cremaster relaxes, allowing the testis to cool by increasing exposed surface area. Contraction can also occur during moments of extreme fear, possibly to help avoid injuring the testes while dealing with a fight or flight situation. 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. 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. 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.