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Damage to the marginal mandibular branch of the facial nerve may cause paralysis of the depressor anguli oris muscle. [1] This may contribute to an asymmetrical smile. [1] This may be corrected by resecting (cutting and removing) the depressor labii inferioris muscle, which has a more significant impact on smiling. [1]
It passes anterior-ward deep to the platysma and depressor anguli oris muscles. It provides motor innervation to muscles of the lower lip and chin: the depressor labii inferioris muscle, depressor anguli oris muscle, and mentalis muscle. [1] It communicates with the mental branch of the inferior alveolar nerve. [citation needed]
The hyoglossus is a thin and quadrilateral extrinsic muscle of the tongue. It originates from the hyoid bone ; it inserts onto the side of the tongue. It is innervated by the hypoglossal nerve (cranial nerve XII) .
The four classical muscles of mastication elevate the mandible (closing the jaw) and move it forward/backward and laterally, facilitating biting and chewing. Other muscles are responsible for opening the jaw, namely the geniohyoid , mylohyoid , and digastric muscles (the lateral pterygoid may play a role).
Muscle Action Risorius: Smirk Buccinator: Aids chewing by holding cheeks flat Levator labii superioris: Elevates upper lip Levator labii superioris alaeque nasi muscle: Snarl Levator anguli oris: Soft smile Nasalis: Flare nostrils Orbicularis oris muscle: Purse Lips Depressor septi nasi: Depresses nasal septum Procerus: Moves skin of forehead
This is a branch of the mandibular nerve (CN V 3), itself a branch of the trigeminal nerve (CN V). [1] It emerges from the mental foramen in the mandible. [2] It divides into three branches beneath the depressor anguli oris muscle. One branch descends to the skin of the chin. Two branches ascend to the skin and mucous membrane of the lower lip.
The jaw elevator muscles develop the main forces used in mastication. The force generated during routine mastication of food such as carrots or meat is about 70 to 150 newtons (16 to 34 lbf ). The maximum masticatory force in some people may reach up to 500 to 700 newtons (110 to 160 lbf ).
The depressor labii inferioris muscle helps to depress and everts the lower lip. [1] It is the most important of the muscles of the lower lip for this function. [1] It is an antagonist of the orbicularis oris muscle. [1] It is needed to expose the mandibular (lower) teeth during smiling. [1]