Zygomaticus major muscle

Origin and insertion

The zygomaticus major muscle originates from the lateral surface of the zygomatic bone, just anterior to the zygomaticotemporal suture and lateral to the origin of zygomaticus minor. It courses inferomedially over the lateral surface of the maxilla to insert to the angle of the mouth. This attachment point is located lateral to zygomaticus minor and medial to risorius muscles.

Here, zygomaticus major interlaces with other muscles that converge towards the angle of the mouth, forming a dense, mobile, fibromuscular mass called the modiolus. It is not entirely clear which muscles exactly attach to the modiolus, but some of the certain ones include depressor anguli oris, buccinator, risorius, zygomaticus major and orbicularis oris muscles.

Relations

Zygomaticus major courses diagonally over the anterior surfaces of the buccinator and masseter muscles. The facial artery and its accompanying vein run between the buccinator and zygomaticus major muscles.

Innervation

Zygomaticus major is innervated by the zygomatic and buccal branches of facial nerve (CN VII).

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Blood supply

Zygomaticus major is mainly supplied by the superior labial artery that branches off the facial artery.

Function

As zygomaticus major contracts, it pulls the angle of the mouth superolaterally. In synergy with risorius, zygomaticus major produces the expression of smiling. This function is followed by the deepening of the nasolabial groove. 

Due to its attachment on the modiolus, the actions of zygomaticus major are coordinated with those of other muscles of the buccolabial group. This integrates movements of the cheeks, lips and chin, enabling various facial expressions and speech.