Muscles of the Head and Neck

Masseter

Action: elevates the mandible

Origin: zygomatic arch

Insertion: mandible

Temporalis

Action: elevates and retracts the mandible

Origin: temporal fossa

Insertion: coronoid process of mandible

Medial pterygoid

Elevates and protracts the mandible and assists with side-to-side movement during mastication

Elevates the mandible as a synergist to the masseter and temporalis

Lateral pterygoid

Depresses and protracts the mandible

works with the medial pterygoid to produce side-to-side movements for grinding food during mastication

What muscles elevate the mandible during mastication (chewing)?

Masseter, temporalis, and medial pterygoid

What muscle depresses the mandible during mastication?

Lateral pterygoid

Sternocleidomastoid

Action: flexes the neck when both sides contract/both muscles act together

individually rotates the head toward the opposite shoulder when acting individually

Origin: sternum and clavicle

Insertion: mastoid process of temporal bone

Scalene muscles

Anterior, middle, and posterior scalenes laterally flex the head/neck when acting individually

When the head and neck are fixed, they elevate the ribs during deep breathing

Head is pulled laterally when acting individually

origin and insertion can switch

when fixators hold the head and neck in place and scalenes work together, ribs are elevated in deep breathing

Trapezius

head movement

The superior portion extends the head

has three parts; Superior part extends the head; other parts discussed later

Splenius capitis & cervicis muscles

Contracting on one side rotates the head and neck to the same side

contracting on both sides extends the head and neck

If contracting on one side, rotates the head and neck to the same side

when contracting on both sides, extends the head and neck

Digastric, stylohyoid, mylohyoid & geniohyoid

Elevate the hyoid bone and raise the tongue and floor of the mouth in preparation for swallowing

Genioglossus

Protrudes the tongue

Hyoglossus

Depresses the tongue

Styloglossus

Elevates and retracts the tongue

Sternohyoid, omohyoid, sternothyroid & thyrohyoid

Depress the pharynx after it is briefly elevated during swallowing, helping move food farther into the pharynx and preventing food from entering the respiratory tract

Pharyngeal constrictor

Contracts sequentially from superior to inferior to push food into the esophagus

What usually happens to the insertion when a muscle contracts?

The insertion is usually pulled toward the origin