Ischiocavernosus muscle

Origin and insertion

Ischiocavernosus originates from the medial aspect of the ischial tuberosity and ischial ramus of the hip bone. The muscle fibers travel in an anterior direction along the medial aspect of the ischial ramus towards the crura of the penis and clitoris. Here, the ischiocavernosus surrounds these structures, inserting into their lateral and inferior surfaces.

Relations

Ischiocavernosus is closely related to the other two superficial perineal muscles within the urogenital triangle of perineum; bulbospongiosus and superficial transverse perineal muscle. Together, these muscles comprise a triangular space filled with adipose tissue. In both sexes, ischiocavernosus is located anterior to the attachments of the superficial transverse perineal muscle. In addition, ischiocavernosus travels laterally to the bulbospongiosus, with the perineal artery and nerve coursing between them.

All superficial perineal muscles, including ischiocavernosus, lie superficial to the perineal membrane. They are separated from the perineal membrane by the subcutaneous perineal space. In turn, the superficial perineal muscles are covered superficially by the deep perineal fascia (of Gallaudet).

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Innervation

Ischiocavernosus is innervated by the deep branch of perineal nerve, which stems from the pudendal nerve. The latter originates from the S2-S4 spinal nerves of the sacral plexus.

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Blood supply

The arterial blood supply to the ischiocavernosus muscle is provided by the perineal artery, a branch of the internal pudendal artery. The latter stems from the internal iliac artery.

Function

Contraction of the ischiocavernosus muscle compresses the crura of the penis/clitoris, pushing the blood away from their roots into the distal parts. The surrounding veins which drain the penis/clitoris are also compressed by ischiocavernosus, restricting venous outflow. This increased pool of venous blood maintains the turgidity (distension) of the penis/clitoris, helping to maintain an erection during sexual arousal and intercourse. In males, ischiocavernosus also acts together to stabilize the penis when fully erect.