Muscles of the Head

There are 656 muscles in the human body. 327 of these muscles are in antagonistic pairs (654) Of these, only 2 muscles are unpaired Obicularis oris Diaphragm

Head Muscles Are grouped into 2 categories: Facial muscles Provide movement for facial expressions Chewing muscles Control the mandible for mastication

Facial Muscles Frontalis Covers the frontal bone Starts at the cranial aponeurosis (a connective tissue that cover the top of the skull) and inserts at the skin of the eyebrows. Functions to wrinkle the forehead and raise the eyebrows.

Occipitalis Covers the posterior portion of the cranium. Starts at the posterior cranial aponeurosis and connect to the skin at the back of the head. Functions to pull the scalp posteriorly (used to wiggle your ears)

Orbicularis Oculi Runs in a circular pattern around the eye. Also lies underneath the eyebrows. Functions to close your eyes, squint, blink, and wink.

Orbicularis Oris A circular muscle that surround the opening of the mouth. Functions to close and compress the lips. Also allows you to protrude your lips. AKA the “kissing” muscle

Buccinator Runs horizontally across the cheek and inserts into the orbicularis oris. Functions to flatten the cheek (when whistling or blowing a trumpet). Also compresses the cheek to hold food in between the teeth during chewing.

Zygomaticus Extends from the corner of the mouth to the cheekbone at a diagonal. This muscle has two bodies (major and minor). Functions to raise the corners of the mouth. Is often referred to as the “smiling” muscle.

Depressor Anguli Oris Found along the side of the chin Functions to depress or pull down the corners of the mouth.

Nasalis Located over the nasal bones. Functions to close and open the nasal opening. Allows you to flare your nostrils.

Chewing Muscles Masseter Runs from the zygomatic process of the temporal bone to the mandible. Covers the lateral surface of the angle of the lower jaw. Functions to close the jaw.

Temporalis A fan-shaped muscle lying on the temporal bone. Passes under the zygomatic process and inserts into the mandible. Functions to raise the jaw, close the mouth, and draw the jaw backward. Acts as a synergist of the masseter

Neck Muscles For the most part, these muscles move the head and the shoulder girdle. These muscles cause the head to: Flex Extend Rotate

Platysma A broad sheet-like muscle that covers the anterolateral neck. Orginates from the connective tissue covering the chest muscles and inserts into the area around the mouth. Functions to pull the lower jaw inferiorly and backward.

Sternocleidomastoid Found diagonally on each side of the neck. Of the 2 heads: the sternum the clavicle The heads fuse and insert into the mastoid process of the temporal bone. If both contract, functions to flex the neck. If one contracts, the head is rotated.

Identify the muscles that are being used in the following facial expressions