Anatomical study of the incisivus labii superioris and inferioris muscles in non‐human primates

The facial muscles have significant roles for vocalization, feeding, and facial expression in both human and non‐human primates. Of these, the anatomy of the incisivus labii superioris (ILS) and incisivus labii inferioris (ILI), which are considered as the accessory bundle of the orbicularis oris (OO) in humans, has rarely been documented in the literature. Our current understanding of the function of the ILS and ILI is that they probably...