Masseter muscle is partly concealed, anteriorly, by the superficial portion. Posteriorly, it is covered by the parotid gland. Along with the other three muscles of mastication (temporalis, medial pterygoid, and lateral pterygoid), the masseter is innervated by the anterior division of the mandibular division (V3) of the trigeminal nerve. The innervation pathway is: gyrus precentralis > genu capsula interna > nucleus motorius nervi trigemini > nervus trigeminus > nervus mandibularis > musculus masseter. The action of the muscle during bilateral contraction of the entire muscle is to elevate the mandible, raising the lower jaw. Elevation of the mandible occurs during the closing
Retractor muscle of the penis Retractor muscle of the penis In some animals the male penis possesses a muscle enabling retraction into the prepuce. The retractor penis muscle occurs in marsupials and carnivorans, but it is absent in humans. A stag's penis forms an S-shaped curve when it is not erect, and is retracted into its preputial sheath by the retractor penis muscle. In Tandonia, the retractor penis inserts at the boundary between the penis and epiphallus. In stallions, the retractor penis muscle is relatively underdeveloped. The retractor muscle contracts to retract the penis into the sheath and relaxes to allow the penis to extend