Buccinator action and facial nerve supply
The buccinator is the thin, square muscle in the wall of the cheek that presses the cheek against the teeth, and the facial nerve supplies it.
Remember
The buccinator presses the cheek against the teeth to keep food on the chewing surfaces, and the facial nerve supplies it, unlike the muscles that close the jaw.
Memory aid
Think of buccinator as the cheek's built-in spatula, pressing food back on to the teeth.
A spatula pushes food back into place, just as the buccinator pushes food back on to the teeth.
The buccinator is a thin, square muscle that forms the muscular wall of the cheek. It runs between the maxilla (the upper jaw bone) and the mandible (the lower jaw bone).
When it contracts, it compresses the cheek against the teeth. During chewing (mastication), the tongue pushes food outwards and the buccinator pushes it back inwards. This keeps the food on the biting surfaces of the teeth and out of the oral vestibule, the space between the cheek and the gums. It also assists with blowing and sucking.
Although it helps with chewing, the buccinator is one of the muscles of facial expression, so the facial nerve supplies it. The muscles that close the jaw, such as masseter (the main muscle that raises the lower jaw), are supplied by the trigeminal nerve (the fifth cranial nerve) instead.
If the buccinator is weak, food collects between the cheek and the teeth, even though the jaw can still clench and the lips can still close. Weak jaw closure suggests a jaw muscle such as masseter, whereas a poor lip seal suggests orbicularis oris, the ring-shaped muscle of the lips. When the facial nerve is not working, food can collect between the teeth and the cheek.
Key facts
- Action
- compresses the cheek against the teeth, helping to keep food on the chewing surfaces.
- Other actions
- it assists with blowing and sucking.
- Position
- a thin, square muscle between the maxilla and the mandible, forming the muscular wall of the cheek.
- Nerve supply
- the facial nerve, because it is a muscle of facial expression.
- Jaw-closing muscles
- muscles such as masseter are supplied by the trigeminal nerve instead.
- Lips
- orbicularis oris, the ring-shaped muscle of the lips, closes the lips, whereas the buccinator acts on the cheek.
- Clinical link
- when the facial nerve is not working, food can collect between the teeth and the cheek.
Exam traps
- Closing the lips to narrow the opening of the mouth is the job of orbicularis oris, the ring-shaped muscle of the lips, rather than the buccinator, which acts on the cheek. Their fibres blend, so the two are easily confused.
- Raising the mandible to close the jaw during biting is the work of jaw-closing muscles such as masseter, which are supplied by the trigeminal nerve. The buccinator also works during chewing, yet its movement is of the cheek rather than the jaw.
- Dysfunction of zygomaticus major, which elevates the corner of the mouth during smiling, does not prevent the cheek pressing food against the teeth.
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