Zygomaticus minor muscle

The zygomaticus minor muscle is a muscle of facial expression. It originates from the zygomatic bone, lateral to the rest of the levator labii superioris muscle, and inserts into the outer part of the upper lip. It draws the upper lip backward, upward, and outward and is used in smiling. It is innervated by the facial nerve (VII).

Structure
The zygomaticus minor muscle passes inferomedially from its origin to its insertion at an angle of approximately 30°. It has a mean width of around 0.5 cm.

Origin
It originates from the lateral aspect of just posterior to the zygomaticomaxillary suture.

Insertion
It inserts into the muscular tissue of the upper lip, blending distally with levator labii superioris muscle.

Innervation
The zygomaticus minor muscle receives motor innervation from the zygomatic branches and buccal branches of the facial nerve (CN VII).

Relations
The zygomaticus minor lies lateral to the rest of levator labii superioris muscle, and medial to its stronger synergist zygomaticus major muscle.

Variation
The zygomaticus minor muscle may have either a straight or a curved course along its length. It may attach to both the upper lip and the lateral alar region. It may be underdeveloped in some people, with its role taken over by nearby synergists. These synergists rarely change shape or position, but any difference in smile is usually imperceptible.

Function
The zygomaticus minor muscle draws the upper lip up, back, and out, such as during smiling.

History
The zygomaticus minor muscle is sometimes referred to as the "zygomatic head" of the levator labii superioris muscle.