Muscle · Pelvis

Superficial transverse perineal

Musculus transversus perinei superficialis

A narrow strip of muscle in the most superficial layer of the perineum, running from the sitting bone inward to the perineal body. It is the smallest of the muscles converging on that knot of tissue, and it is often thin, one-sided or missing altogether. Its contribution is to steady the perineal body from the side: that structure is the common anchor for the anal sphincter behind, the deeper perineal muscles above and the bulbospongiosus in front, and it is only as useful as the tissues holding it in place. This is one of them, and it is the reason the perineal body is described as a crossroads rather than as a single muscle's attachment.