Superficial transverse perineal muscle

The Transversus perinei superficialis (Transversus perinei; Superficial transverse perineal muscle) is a narrow muscular slip, which passes more or less transversely across the perineal space in front of the anus.

Origin and insertion
It arises by tendinous fibers from the inner and forepart of the tuberosity of the ischium, and, running medialward, is inserted into the central tendinous point of the perineum, joining in this situation with the muscle of the opposite side, with the Sphincter ani externus behind, and with the Bulbocavernosus in front.

In some cases, the fibers of the deeper layer of the Sphincter ani externus decussate in front of the anus and are continued into this muscle. Occasionally it gives off fibers, which join with the Bulbocavernosus of the same side.

Variations are numerous. It may be absent or double, or insert into Bulbocavernosus or External sphincter.