Cremaster is a paired muscle of the pelvis and perineum that is fully developed only in the external genitalia of males. Being located between the internal and external layers of spermatic fascia, cremaster covers the testes and spermatic cord. Some remnants of the muscle are also present in women, located adjacent to the ligaments of the uterus.
By contracting, the cremaster muscle pulls the testes superiorly (retraction) towards the inguinal canal. This action protects the testes and sperm cells from the negative environmental factors (e.g. extreme temperature changes).
Lateral part: Lower edge of internal abdominal oblique and transversus abdominis muscles, inguinal ligament
Medial part: Pubic tubercle, lateral part of pubic crest
|Insertion||Tunica vaginalis of testis|
|Action||Retraction of testis|
|Innervation||Genital branch of genitofemoral nerve (L1, L2)|
|Blood supply||Cremasteric branch of inferior epigastric artery|
In this article, we will discuss the anatomy and function of the cremaster muscle.
The detailed structure of the cremaster muscle is yet to be determined. According to the majority of anatomical literature, the cremaster muscle is considered as a striated muscle. However, recent studies on the human cadavers indicate that this muscle contains a large number of smooth muscle fibers that are organized in the muscle bundles and dispersed between the striated muscle fibers.
Further histological studies also found that some nerve endings and plexuses interlace with these muscle fibers. Along with the genitofemoral nerve, these nerve endings and plexuses are suggested to provide additional autonomic innervation for this muscle.
Origin and insertion
The cremaster muscle consists of two parts; lateral and medial. The lateral part of cremaster is mainly derived from the lower fibers of the transversus abdominis muscle or from the internal abdominal oblique muscle and inguinal ligament.
Variable and occasionally absent, the medial part of the muscle originates from the pubic tubercle and lateral part of the pubic crest. The medial fibers fuse with the lateral ones and pass inferiorly, covering the spermatic cord. Upon entering the scrotum, cremaster forms a thin network of muscle fascicles that insert onto the inferior aspect of tunica vaginalis, a serous membrane that covers the testes.
The cremasteric muscle fibers unite with the surrounding loose connective tissue to comprise a thin covering for the spermatic cord known as the cremasteric fascia. It extends through the scrotum and around the testis, being situated deep to the external spermatic fascia.
The cremasteric artery and vein and genital branch of genitofemoral nerve are located between the external spermatic fascia and cremasteric fascia.
Since the internal genitalia of women don't require the protective role of cremaster as they are placed within the body, this muscle in women is not fully developed. Some remnants of the muscle are in fact present near the distal portion of the round ligament of uterus.
Explore this study unit to find more articles, videos and quizzes to learn everything about the function of cremaster within male reproductive system.
Cremaster is innervated by sympathetic and somatic fibers of the genital branch of genitofemoral nerve (L1, L2).
Cremaster is supplied by the cremasteric artery, a branch of inferior epigastric artery.
The main action of the cremaster muscle is to pull the testes superiorly towards the superficial inguinal ring. This involuntary action is known as the cremasteric reflex, and its function is to bring the testes closer to the warm environment of the body when they are exposed to the low outside temperatures.
The cremasteric reflex can be provoked and tested by stroking the skin of the medial aspect of the thigh as well as applying cold stimuli in the same location. This stimulates the ilioinguinal nerve, which consequently activates the genital branch of genitofemoral nerve that innervates and activates the muscle. This reflex protects the testes from severe temperature changes, adjusting the temperature within them for adequate sperm production.