Muscles of the head
The muscles of the head are fundamentally different from the muscles of the limbs: facial muscles are woven directly into the skin (and not into the bones), which allows you to create facial expressions. Masticatory muscles, on the contrary, work like classic levers, moving the lower jaw.
Facial muscles
The facial muscles are innervated by the facial nerve (VII pair of cranial nerves). When it is damaged (Bell's palsy), half of the face “sags” - the patient cannot close an eye, wrinkle his forehead or smile on the affected side.
Main facial muscles:
- Orbicularis oculi muscle - closes the eye, squeezes the eyelids
- Orbicularis oris muscle - compresses and extends lips (when kissing, whistling)
- Lelevator anguli oris muscle - forms a smile
- Muscle depressor anguli oris - creates an expression of sadness
- Buccal muscle (m. buccinator) - presses the cheek to the teeth, is involved in chewing and playing wind instruments
- Frontal belly of the occipitofrontal muscle - raises the eyebrows, forms wrinkles on the forehead
In total, there are more than 20 facial muscles, working in various combinations. Scientists have identified about 10,000 facial expressions that we are capable of creating.
Chewing muscles
Four pairs of masticatory muscles are innervated by the trigeminal nerve (V pair):
| Muscle | Function |
|---|---|
| Chewing (masseter) | Raises the lower jaw |
| Temporal (temporalis) | Lifts and pulls back |
| Medial pterygoid | Raises and moves to the side |
| Lateral pterygoid | Opens his mouth, moves forward |
The masseter and temporal muscles are the most powerful. The chewing muscle develops a force of up to 70 kg, which makes a human bite comparable to the bite of some predators.
Clinical significance
Spasm of the masticatory muscles (trismus) can occur with tetanus, inflammatory processes and stress (bruxism - grinding teeth in sleep). Knowledge of the attachment points of facial muscles is used in cosmetology when injecting botulinum toxin to smooth out wrinkles.
In the Humio](/) app, you can view each facial and masticatory muscle separately - rotate the 3D model of the head and study the attachment points.