Buccinator muscle

Origin and insertion

Its superior part arises from the outer surface of the alveolar process of the maxilla opposite to the three maxillary molar teeth. The inferior part also arises from the alveolar part of the mandible opposite to the three mandibular molar teeth. The posterior part of the buccinator originates from the anterior margin of the pterygomandibular raphe, a tendinous band behind the third molar spanning from the pterygoid hamulus to the posterior end of the mylohyoid line. Some of the back fibers of posterior origin attach to the buccinator crest, the small ridge on the retromolar triangle (anterior, horizontal portion of retromolar fossa). Additionally, some fibers of the buccinator arise from the pterygomaxillary raphe, a fibrous band that extends from the pterygoid hamulus to maxillary tuberosity.

Converging towards the angle of the mouth, the three parts of buccinator fill the space between the upper and lower jaws. At the angle of the mouth, the buccinator fibers interlace with other muscles that attach at the same site, including orbicularis oris, risorius, depressor anguli oris and zygomaticus major. These muscles blend and form a dense fibromuscular mass called the modiolus.

After forming the modiolus, the fibers of the buccinator continue towards the upper and lower lips to comprise the peripheral part of orbicularis oris muscle. 

• The uppermost and lowermost fibers of the buccinator diverge and enter the superior and inferior lips, respectively. 
• The central fibers of the buccinator split into two and decussate so that the inferior half enters the superior lip, and the superior half enters the inferior lip.

Relations

The buccinator is the main component of the cheeks along with a considerable amount of subcutaneous fat. The buccal fat pad (of Bichat) covers the outer surface of the deep part of buccinator, separating it from the ramus of mandible, masseter and temporalis muscles. 

The buccinator lies in the same plane and anteriorly to the superior pharyngeal constrictor, being separated from it by the pterygomandibular raphe. Both muscles are covered by the buccopharyngeal fascia. The posterior border of the buccinator is pierced by the tensor veli palatini near its attachment point to the pterygomandibular raphe.

Superior and inferior parts of the muscle lie deep to the zygomaticus major, risorius, levator and depressor anguli oris muscles. This surface is also crossed by the facial artery and vein and the branches of facial (CN VII) and buccal nerves. The duct of the parotid gland courses over this surface as well, and pierces the buccinator at the level of the third upper molar tooth. It then courses shortly over its deep surface and opens into the oral cavity second upper molar tooth. The deep surface of the muscle is related to the structures of the oral cavity; buccal glands and mucous membrane of the mouth.

Innervation

The buccinator is innervated by the buccal branches of facial nerve (CN VII). 

Blood supply

The buccinator receives arterial blood supply mainly from the buccal artery, a branch of the maxillary artery; and some branches of the facial artery.

Function

The buccinator maintains the tightness of the cheeks and presses them against the teeth during chewing. It also assists the tongue to keep the bolus of food central in the oral cavity. This function is important to prevent it from escaping into the oral vestibule, as well as pushing any food that entered the vestibule back into the oral cavity. Buccinator also prevents cheeks from inverting in between the occlusal surfaces of the teeth and being bitten.

The buccinator muscle has another interesting function, and that is expelling the air from the inflated vestibule while playing a wind instrument such as the trumpet. This is why the buccinator muscle is also called the "trumpet muscle".

Strengthen your knowledge about the buccinator muscle with our quiz that covers everything you need to know about the muscles of facial expression.