Which of the following muscles is innervated by the marginal mandibular branch of the facial nerve?

Explanation

## Marginal Mandibular Branch of Facial Nerve **Key Point:** The marginal mandibular branch of CN VII is the lowest terminal branch of the facial nerve within the parotid gland and supplies muscles of the lower lip and chin. ### Muscles Supplied by Marginal Mandibular Branch | Muscle | Action | Innervation | |--------|--------|-------------| | Depressor anguli oris | Depresses angle of mouth | Marginal mandibular (CN VII) | | Depressor labii inferioris | Depresses lower lip | Marginal mandibular (CN VII) | | Mentalis | Wrinkles chin skin | Marginal mandibular (CN VII) | | Buccinator | Compresses cheek | Buccal branch (CN VII) | | Orbicularis oris | Closes/purses lips | Buccal branch (CN VII) | **High-Yield:** The marginal mandibular branch is clinically significant because it runs along the inferior border of the mandible and is at risk during neck dissections, parotid surgery, or facelift procedures. Injury causes drooping of the lower lip on the affected side. **Mnemonic:** **MAD** — Marginal mandibular branch supplies: **M**entalis, **A**nguli oris (depressor), **D**epressor labii inferioris. **Clinical Pearl:** In a patient with facial nerve palsy, inability to depress the lower lip and loss of the nasolabial fold on one side indicates marginal mandibular branch involvement. **Tip:** Remember that levator muscles of the upper face (levator labii superioris, levator palpebrae superioris) are supplied by the buccal and zygomatic branches, NOT the marginal mandibular branch. [cite:Clinically Oriented Anatomy 8e Ch 8]