The muscle that is most often injured by a tear of the perineum is innervated by which of the following?

The pudendal nerve (from S2-S4) is the principal nerve to innervate structures of the perineum, including sensory innervation to the genitalia, and motor innervation to muscles of the perineum, the external urethral sphincter, and the external anal sphincter. This innervation may have clinical significance, as babies can also have uterine prolapse, which can be due either to congenital weakness in the pelvic musculature or to defects in innervation. The inferior gluteal nerve supplies the gluteus maximus. The pelvic splanchnic nerve supplies the pelvic viscera the inferior hypogastric and pelvic plexuses. The posterior femoral cutaneous nerve supplies the skin of the buttock and upper poions of the medial and posterior aspects of the thigh. Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 2. Maternal Anatomy. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.