The Nostrils and Lips
Nasalis ("nay-ZAL-iss") crosses over the center of the nose from the maxilla. It compresses the nostrils and lowers them.
The levator labii group ("LAY-bee-ee") originates on a wide swath of the zygomatic bone and inserts into the corner of the nose and the upper lip. They work together to pull the upper lip and the corner of the nose upward.
Nearby zygomaticus ("zigh-go-MAT-ih-cus") originates on the lateral front corner of the zygomatic bone and inserts into the corner of the mouth. Between zygomaticus and the levator labii group, underneath, is caninus ("cuh-NINE-us"), which attaches to the zygomatic bone and the corner of the mouth. These muscles pull the corner of themouth outward and upward into a smile.
Risorius ("rih-SORE-ee-us") attaches to the flesh of the cheek and the corner of the mouth. Risorius by itself creates a dubious smile, pulling the corner of the mouth flatly back. Beneath risorius is buccinator ("BUCK-sin-ate-or"), which originates on the jaws on either side of the teeth and the deep flesh of the cheek. Its action on the corner of the mouth is similar, but also curls it inward, creating an even more dubious smile.
Four muscles below the lip could be massed as the inferior labii group. All originate on the mandible. Depressor anguli oris ("ANG-you-lee OR-iss) pulls down the angle of the mouth, hence its name. Depressor labii inferioris pulls the lower lip down and laterally. Mentalis ("men-TAL-iss") pushes the lower lip upward. The facial portion of platysma pulls the corner of the mouth down and dramatically outward; this happens almost involuntarily when the throat portion of platysma is strongly tensed.
The crowning form of the lips is orbicularis oris, which closes and puckers them.