Question

Know the origin/insertion/action of the following

: zygomaticus major, masseter

Answer 1

Answer :

zygomaticus major:

Origin: anterior of zygomatic.

Insertion: modiolus of mouth.

Actions :draws angle of mouth upward and laterally

The zygomaticus major is a muscle of the human body. It is a muscle of facial expression which draws the angle of the mouth superiorly and posteriorly to allow one to smile.Like all muscles of facial expression, the zygomatic major is innervated by the facial nerve (the seventh cranial nerve), more specifically, the buccal and zygomatic branches of the facial nerve.

Function :It raises the corners of the mouth when a person smiles. Usually a single unit, Dimples are caused by variations in form.It is thought that dimples are caused by bifid zygomaticus major muscle.

Masseter muscle:

Origin :zygomatic arch and maxillary process of zygomatic bone.

Insertion: Angle and lateral surface of ramus of mandible, coronoid process.

Actions :elevation (as in closing of the mouth) and protrusion of mandible.

In human anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it is the most superficial and one of the strongest.

Function:

The action of the muscle during bilateral contraction of the entire muscle is to elevate the mandible, raising the lower jaw. Elevation of the mandible occurs during the closing of the jaws. The masseter parallels the medial pterygoid muscle, but it is stronger and superficial fibres can cause protrusion.