The buccinator muscle joins the orbicularis oris sphincteric complex. The deepest muscle of facial expression, it forms a quadralateral canopy from maxillary to mandibular alveoli, and from oral commissure to pterygomandibular raphe. The buccinator forces food against the teeth during chewing and permits forceful blowing of air through the lips.

The muscle is innervated by the buccal branch of the facial nerve, which crosses the masseter along the parotid duct, branches to the superficial surface of the muscle, and continues through the buccal fat pad to innervated medial upper lip musculature, The buccal branch of the mandibular division of the trigeminal nerve provides sensation to mucosa via a deeper traverse across the medial pterygoid muscle.

The buccal fat pad separates the buccinator from the masseter. Beyond the anterior border of the masseter, the buccomasseteric fascia covers the fat pad. The parotid duct crosses the masseter, enters the buccal fat pad, and then perforates the superior midportion of the buccinator to empty into the oral cavity. The deep surface of the buccinator is adherent to mucosa. If approached through a nasolabial incision, the buccinator lies immediately lateral to the orbicularis oris muscle. It is deep to the orbicular, the zygomaticus major, and levator anguli oris muscles (Fig. 193.1). The surgeon also encounters the masseter muscle, buccal fat pad, and buccomasseteric fascia. Between the buccomasseteric fascia and the buccinator are an areolar connective tissue plane and fat pad that facilitate blunt separation of the muscle.

The facial artery forms the blood supply of the BMIF (4, 7). It originates from the external carotid and ascends the neck, sprouting submandibular gland, platysma, and submental branches. After the artery crosses the antegonial notch of the mandible, it gives off twigs to the masseter and depressor anguli oris muscles (Figs. 193.1 and 193.2). Under cover of the lip depressors, the facial artery branches into the inferior labial artery that encircles the lower lip. Between the mandible and maxilla, the artery obliquely crosses and supplies two or three branches to the anterior portion of the buccinator (5). After it courses between and supplies twigs to the zygomaticus and levator anguli oris, the facial artery branches into the superior labial artery which runs across the upper lip. After sprouting the lateral nasal artery, the facial artery usually terminates through the levator labii superioris alaeque nasi as the angular artery.