And Muscles of the Head and Neck The Naming of Muscles And Muscles of the Head and Neck

Naming Muscles Muscles are named according to: Location (frontalis – forehead) Size (gluteus maximus) Direction (external abdominal oblique) Number of origins (biceps femoris) Location of origin and insertion (sternocleidomastoid) Action (flexor carpi ulnaris) Shape (deltoid – triangular)

Muscles of the Head

There are 656 muscles in the human body. 327 of these muscles are in antagonistic pairs (654) 2 muscles are unpaired orbicularis oris diaphragm

Head Muscles Have many specific functions. Are grouped into 2 categories: 1. Facial muscles Provide movement for facial expressions Are unique in that they insert into soft tissues such as other muscles or skin 2. Chewing muscles Control the mandible for mastication Begin the breakdown of food in the digestive process

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

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

Orbicularis Oculi Has fibers that run in a circular pattern around the eye. Also lies underneath the eyebrows. Functions to close your eyes, squint, blink, and wink. Also tightens the skin on the forehead.

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

Muscles that move the orbicularis oris Levator labii superioris nasi Levator labii superioris Zygomaticus minor Zygomaticus major Levator anguli superioris Orbibularis oris Node (corner of mouth) Risorius Platysma Despressor anguli oris Depressor labii inferioris Mentalis

Buccinator A horizontal muscle that runs across the cheek starts at the lateral angle of the mandible and inserts into the orbicularis oris. Functions to flatten the cheek (when whistling or blowing a trumpet). Also somewhat involved in chewing. It 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 the larger of the two, found more laterally minor the smaller of the two, found more medially Functions to raise the corners of the mouth. Is often referred to as the “smiling” muscle.

zygomaticus

Depressor Anguli Oris Originates along the side of the chin and tapers to inserts at the corner (node) of the orbicularis oris. Functions to depress or pull down the corners of the mouth.

Nasalis Two sets of muscles located over the nasal bones. One is lateral One is vertical Functions to close and open the nasal opening. Allows you to flare and close your nostrils.

Muscles of Mastication

Masseter Runs from the zygomatic process of the temporal bone to the mandible. Covers the lateral surface of the angle of the lower jaw. Is the primary muscle involved in closing the jaw; does so by elevating the mandible.

Temporalis A fan-shaped muscle overlying the temporal bone. Passes underneath the zygomatic process and inserts into the mandible. Acts as a synergist of the masseter. Functions to raise the jaw and draw the jaw backward.

Neck Muscles For the most part, these muscles move the head and the shoulder girdle. These muscles cause the head: Extension Flexion Rotation

Platysma A broad, sheet-like muscle that covers the anterolateral surface of the 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 Paired muscles found diagonally on each side of the neck. Originates at two places: from the sternum from 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.