Location and Layer
This muscle is part of the pelvic floor, which is formed by the perineal muscles and conventionally divided into three layers.
The ischiocavernosus muscle (m. ischiocavernosus) is part of the superficial layer of the urogenital region, located beneath the skin and superficial fascia. Topographically, it lies laterally along the inferomedial margins of the puboischiadic rami of the hip bone.
The fascia forms sheaths for the three superficial muscles: medially lies the bulbospongiosus muscle (m. bulbospongiosus), laterally the ischiocavernosus muscle (m. ischiocavernosus), and posteriorly the superficial transverse perineal muscle (m. transversus perinei superficialis). The tendons of the superficial layer muscles unite in the midline at the perineal body (centrum tendineum perinei).
Topography in Males
In males, the ischiocavernosus muscle is associated with the structures of the penis (penis).
It covers the proximal parts of the two corpora cavernosa penis (corpus cavernosum penis) — specifically, the crura of the penis (crura penis). These crura attach to the inferior rami of the pubic and ischial bones.
The corpora cavernosa are surrounded by the tunica albuginea (tunica albuginea). The fascia of the penis (fascia penis) is a continuation of the deep perineal fascia and covers the corpora superficial to the tunica albuginea.
Topography in Females
In females, the topography of the m. ischiocavernosus is related to the crura of the clitoris (crura clitoridis).
In descriptions of the female perineum, the ischiocavernosus muscle is described as originating from the ischium and covering the region of the clitoris.
In the superficial layer, the bulbospongiosus muscle (m. bulbospongiosus) is located medially. In females, deep to each bulbospongiosus muscle lies the vestibular bulb (bulbus vestibuli), a robust venous plexus homologous to the bulb of the penis in males.
Adjacent Structures of the Urogenital Region
The same superficial layer and urogenital diaphragm include the following structures:
- Bulbospongiosus muscle (m. bulbospongiosus) — located medially in the superficial layer. In males, it covers the bulb of the penis; in females, the vestibular bulb lies deep to it.
- Superficial transverse perineal muscle (m. transversus perinei superficialis) — located posteriorly, running from the ischial tuberosity to the perineal body.
- Urogenital diaphragm (diaphragma urogenitale) — located deep to the superficial muscle layer, forming the middle layer. It consists of fused fascial layers stretched between the pubic bones and includes the deep transverse perineal muscle (m. transversus perinei profundus).