Facial & Neck Muscles Actions, Insertion, Origin, & Nerve Supply

What action does the sternocleidomastoid muscle perform when contracted bilaterally?

Flexes the head.

What are the origins of the sternocleidomastoid muscle?

Manubrium of the sternum and the medial portion of the clavicle.

Where does the sternocleidomastoid muscle insert?

Mastoid process of the temporal bone.

What happens when only one sternocleidomastoid muscle contracts?

It turns the head to the opposite shoulder and tilts or flexes on the same side.

What is the action of the scalenes during inspiration?

Elevate the first two ribs.

What is the origin of the scalenes?

Transverse processes of cervical vertebrae.

What bones do the scalenes insert on?

First two ribs.

What key actions do the anterior, middle, and posterior scalene muscles perform?

They assist in neck flexion and aid in rotation of the neck.

What is the action of the digastric muscle?

Opens the mouth and depresses the mandible.

What role does the stylohyoid muscle play when swallowing?

Elevates and retracts the hyoid, elongating the floor of the mouth.

What does the mylohyoid muscle do?

Elevates the hyoid and the floor of the mouth, allowing the tongue to exert upward pressure for food.

What is the function of the geniohyoid muscle?

Elevates the hyoid and widens the pharynx for food.

What does the sternohyoid muscle do?

Depresses the larynx and hyoid bone when the mandible is fixed.

How does the thyrohyoid muscle function?

Depresses the hyoid bone or elevates the larynx if the bone is fixed.

What is the primary action of the sternothyroid muscle?

Depresses the larynx and hyoid bone.

What is the action of the omohyoid muscle?

Depresses and retracts the hyoid bone.

What muscle closes the jaw and elevates the mandible?

Temporalis

Which muscle is primarily responsible for protracting the mandible?

Lateral pterygoid

What is the action of the masseter muscle?

Closes jaw and elevates mandible

Which muscle works synergistically with the lateral pterygoid?

Medial pterygoid

What muscle keeps the mandible in its resting position?

Temporalis

What is the action of the medial pterygoid muscle?

Acts with lateral pterygoid in elevation and protraction of the mandible.

Which muscle is responsible for side-to-side grinding movements of the mandible?

Lateral pterygoid

What is the action of the Buccinator muscle?

Compresses cheek, draws corners of mouth laterally, holds food between teeth while chewing.

What is the action of the Corrugator supercilii?

Draws eyebrows medially and inferiorly; wrinkles skin of forehead.

What action does the Depressor anguli oris perform?

Draws corners of mouth inferiorly and laterally, creating a frown.

What is the primary action of the Depressor labii inferioris?

Depresses lower lip (pouting).

What does the Levator labii superioris do?

Opens lips by elevating and furrowing the upper lip.

What is the action of the Mentalis muscle?

Wrinkles chin and protrudes the lower lip.

What does the frontal belly of the Epicranius do?

Elevates eyebrows and wrinkles the skin of the forehead.

What is the main function of the Occipital belly of the Epicranius?

Fixes aponeurosis and pulls the scalp posteriorly.

What action does the Orbicularis oris perform?

Closes lips, purses and protrudes lips (kissing or whistling).

What is the function of the Orbicularis oculi?

Closes eyes (blinking, squinting) and draws eyebrows interiorly.

What does the Risorius muscle do?

Draws corners of lips laterally and works with zygomaticus to tense lips.

What is the action of the Zygomaticus muscle?

Raises lateral corners of mouth (smiling).