Learning Objective: Describe the anatomy, innervation, and clinical significance of the muscles of facial expression, including their attachments, actions, and groups.
The muscles of facial expression lie within the subcutaneous tissue of the face. They originate from bone or fascia and insert onto the skin, allowing facial movement by pulling on the skin. All these muscles develop from the second pharyngeal arch and are innervated by branches of the facial nerve (CN VII).
They are divided into three functional groups:
- Orbital group
- Nasal group
- Oral group
Orbital Group
Orbicularis Oculi
- Parts: Palpebral, Lacrimal, and Orbital
- Attachments: From the medial orbital margin, palpebral ligament, and lacrimal bone → skin around orbit & eyelid.
- Actions:
- Palpebral part – gently closes eyelids
- Lacrimal part – drains tears
- Orbital part – tightly closes eyelids
- Innervation: Temporal & zygomatic branches of CN VII
Corrugator Supercilii
- Attachments: From the medial superciliary arch → skin of eyebrow
- Action: Draws eyebrows medially and downward (frowning)
- Innervation: Temporal branches of CN VII
🩺 Clinical Note – Facial Nerve Paralysis (Orbital muscles): Loss of eyelid closure → exposure keratitis. Drooping of lower lid → ectropion and lacrimal fluid pooling
Nasal Group
Nasalis
- Parts: Transverse and Alar
- Attachments:
- Transverse part – from maxilla → nasal dorsum aponeurosis
- Alar part – from maxilla → alar cartilage
- Actions:
- Transverse – compresses the nasal opening
- Alar – widens the nasal opening
- Innervation: Buccal branches of CN VII
Procerus
- Attachments: From the nasal bone → skin of the lower forehead
- Action: Pulls eyebrows downward, forming transverse wrinkles
- Innervation: Buccal branches of CN VII
Depressor Septi Nasi
- Attachments: Maxilla (above medial incisor) → nasal septum
- Action: Pulls the septum inferiorly, widening the nostrils
- Innervation: Buccal branches of CN VII
Oral Group
Orbicularis Oris
- Attachments: Maxilla & other facial muscles → skin & mucous membrane of lips
- Action: Closes lips, narrows mouth opening
- Innervation: Buccal branches of CN VII
Buccinator
- Attachments: Maxilla & mandible → fibers blend with orbicularis oris
- Action: Compresses cheek against teeth (prevents food pocketing)
- Innervation: Buccal branches of CN VII
Minor Oral Muscles
- Upper group: Risorius, Zygomaticus major/minor, Levator labii superioris, Levator labii superioris alaeque nasi, Levator anguli oris
- Lower group: Depressor anguli oris, Depressor labii inferioris, Mentalis
🩺 Clinical Note – Facial Nerve Paralysis (Oral muscles): Drooping mouth corner → food collects in cheek pocket. Mouth drawn toward the healthy side when smiling
