09/02/2026
You don’t need to memorize a long list of muscles… you just need to understand the pattern 😗
‘Face the Beat’ Muscles of Facial Expressions Rap
✅ Motor innervation
Primarily supplied by CN VII (facial nerve)
*The nerve exits the skull through the stylomastoid foramen
*It then travels through the parotid gland, where it forms a plexus and divides into 5 terminal branches
✅ Key Distinction
The muscles of facial expression are unusual because many insert into the skin rather than bone, allowing them to move the overlying skin and create facial expressions.
Around the eye
*Close the eyelids
*Protect the eye from excessive light and foreign material
*Important clinically when testing facial nerve function
Around the mouth
*Elevate, depress, retract, or purse the lips
*Essential for smiling, frowning, speaking, and eating
Around the nose
*Alter the shape of the nasal openings
*Help control movement of the nostrils
Around the ear
*Small muscles that can move the external ear
*Much less clinically significant in most people
HIGH-YIELD CLINICAL PEARL
A CN VII lesion can cause weakness of the muscles of facial expression on the ipsilateral side.
Think:
*Difficulty closing the eye
*lattened facial folds
*Drooping of the corner of the mouth
*Difficulty smiling or puffing out the cheek
UMN vs LMN
A lower motor neuron CN 7 lesion → weakness of the entire ipsilateral face.
A supranuclear/UMN lesion → classically causes weakness of the contralateral lower face, while forehead movement is relatively preserved due to bilateral cortical innervation.
REV MED Anatomy and Medical Education
