Zygomaticus major muscle
Zygomaticus major is a thin paired facial muscle that extends diagonally from the zygomatic bone (hence the name) to the angle of the mouth. It belongs to the buccolabial group of facial muscles along with levator labii superioris alaeque nasi, levator labii superioris, zygomaticus major, zygomaticus minor, levator anguli oris, risorius, depressor labii inferioris, depressor anguli oris, mentalis, orbicularis oris, incisivus superior and inferior and buccinator muscles. These muscles form the structure and carry out the functions of the cheeks and lips.
The main action of zygomaticus major is to pull the angle of the mouth superolaterally. In coordination with other buccolabial muscles, it facilitates speech and creates facial expressions. Along with risorius, zygomaticus major contributes to laughing, which is why they are deemed the “laughing muscles”.
|Origin||(Posterior part of) Lateral aspect of zygomatic bone|
|Insertion||Modiolus, blends with muscles of upper lip|
|Function||Elevates and everts angle of mouth|
|Innervation||Buccal and zgyomatic branches of facial nerve (CN VII)|
|Blood supply||Superior labial artery (facial artery)|
This article will teach you all you need to know about the anatomy and functions of the 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.
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.
Zygomaticus major is innervated by the zygomatic and buccal branches of facial nerve (CN VII).
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Zygomaticus major is mainly supplied by the superior labial artery that branches off the facial artery.
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.