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Learning Objectives

By the end of this section, you will be able to:

Identify, locate, and describe the origin, insertion and function of three muscles in the head and neck.

We will consider the following three muscles:

  • Masseter
  • Sternocleidomastoid
  • Trapezius

Masseter

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         This cheek muscle has a superficial and a deep part and is named after its function.

originates on the zygomatic arch (bony ridge formed by both the zygomatic and temporal bones) and maxilla

It inserts on the ramus of the mandible

This powerful muscle elevates the mandible during the act of chewing, otherwise known as mastication. The joint involved is the temporomandibular joint (TMJ).

Sternocleidomastoid

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         This long narrow muscle has two heads and is in the neck. It is named for two of its origin sites and its one insertion site. Can you see from the name and image what these sites might be?  

It originates from the manubrium of the sternum and from the clavicle.

It inserts on the mastoid process of the temporal bone.

Acting singly this muscle turns the head either to the right or left (rotation) and laterally flexes the neck. However, acting together, this muscle tips the head forward (flexes the neck) and raises the manubrium.

TRAPEZIUS

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         This is a large, flat, triangular sheet of muscle.  It covers the posterior neck region and the upper region of the back. It attaches the axial skeleton to the upper appendicular skeleton. Can you see this on the diagram? Looking at the diagram, why do you think it’s named “trapezius”?

Visit this AnatomyZone site. Move the image around in 3D to observe and make a note of this muscle’s sites of origin and insertion. Remember that you can click on the bones to recall their names. Make a visual note on how this muscle connects the axial and appendicular skeletons. Based on this muscle’s multiple origin and insertion sites, can you guess what its function may be? See if you got this right using the dropdowns below.

It originates on the occipital bone of the skull, and on the seventh cervical, and all thoracic vertebrae.

It inserts on the clavicle, and the acromion and spine of the scapula. 

It moves and stabilizes the scapula and helps bend the head laterally and raise the head (extension).

Test Your Knowledge