Human muscular system - head, neck, & trunk

22 terms by chungdanield 

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Corrugator supercilii

Small muscle. Activity associated with that of orbicularis oculi. Origin: arch of frontal bone above nasal bone. Insertion: skin of eyebrow. Action: draws eyebrow medially, inferiorly, wrinkles skin of forehead vertically.

Levator labii superioris

Thin muscle between orbicularis oris, inferior eye margin. Origin: zygomatic bone, infraorbital margin of maxilla. Insertion: skin, muscle of upper lip and border of nostril. Action: raises, furrows upper lip. Opens lips.

Buccinator

Principal muscle of cheek. Runs horizontally, deep to masseter. Origin: molar region of maxilla, mandible. Insertion: orbicularis oris. Action: draws corner of mouth laterally. Compresses cheek (as in whistling). Holds food between teeth during chewing.

Risorius

Slender muscle. Runs inferior, lateral to zygomaticus. Origin: fascia of masseter muscle. Insertion: skin at angle of mouth. Action: draws corner of lip laterally. Tenses lip. Zygomaticus synergist.

Mentalis

One of muscle pair forming V-shaped muscle mass on chin. Origin: mandible below incisors. Insertion: skin of chin. Action: protrudes lower lip. Wrinkles chin.

Depressor labii inferioris

Small muscle from lower lip to mandible. Origin: body of mandible lateral to its midline. Insertion: skin and muscle of lower lip. Action: draws lower lip inferiorly.

Depressor anguli oris

Small muscle lateral to depressor labii inferioris. Origin: body of mandible below incisors. Insertion: skin and muscle at angle of mouth below insertion of zygomaticus. Action: zygomaticus antagonist. Draws corners of mouth downward and laterally.

Occipitalis/occipital belly

Epicranius. Bipartite muscle consisting of frontal and occipital parts, which covers dome of skull. Origin: occipital and temporal bones. Insertion: galea aponeurotica. Action: occipital belly fixes aponeurosis and pulls scalp posteriorly.

Orbicularis oculi

Tripartite sphincter muscle of eyelids. Origin: frontal and maxillary bones and ligaments around orbit. Insertion: encircles orbit and inserts in tissue of eyelid. Action: various parts can be activated individually. Closes eye. Produces blinking, squinting, and draws eyebrows inferiorly.

Zygomaticus

Extends diagonally from corner of mouth to cheekbone. Origin: zygomatic bone. Insertion: skin and muscle at corner of mouth. Action: raises lateral corners of mouth upward (smiling muscle).

Masseter

Covers lateral aspect of mandibular ramus. Can be palpated on forcible closure of jaws. Origin: zygomatic arch and maxilla. Insertion: angle and ramus of mandible. Action: closes jaw and elevates mandible.

Temporalis

Fan-shaped muscle lying over parts of frontal, parietal, and temporal bones. Origin: temporal fossa. Insertion: coronoid process of mandible. Action: closes jaw. Elevates and retracts mandible.

Orbicularis oris

Multilayered muscle of lips with fibers that run in many different directions, mostly circularly. Origin: arises indirectly from maxilla and mandible. Fibers blended with fibers of other muscles associated with lips. Insertion: encircles mouth. Inserts into muscle and skin at angles of mouth. Action: closes mouth. Purses and protrudes lips (kissing and whistling muscle).

Frontalis/frontal belly

Epicranius. Bipartite muscle consisting of frontal and occipital parts, which covers dome of skull. Origin: galea aponeurotica (cranial aponeurosis). Insertion: skin of eyebrows and root of nose. Action: with aponeurosis fixed, frontal belly raises eyebrows.

Sternothyroid

Lateral and deep to sternohyoid. Origin: posterior surface of manubrium. Insertion: thyroid cartilage of larynx. Action: acting with sternohyoid and omohyoid (all inferior to hyoid bone), depresses larynx and hyoid bone if mandible is fixed. May also flex skull.

Sternocleidomastoid

2-headed muscle located deep to platysma on anterolateral surface of neck. Fleshy parts on either side indicate limits of anterior and posterior triangles of neck. Origin: manubrium of sternum and medial portion of clavical. Insertion: mastoid process of temporal bone and superior nuchal line of occipital bone. Action: simultaneous contraction of both muscles of pair causes flexion of neck forward, generally against resistance.

Sternocleidomastoid (cont.)

Acting independently, rotate head toward shoulder on opposite side.

Stylohyoid

Slender muscle parallels posterior border of digastric. Below angle of jaw. Origin: styloid process of temporal. Insertion: hyoid bone. Action: elevates and retracts hyoid bone.

Sternohyoid

Runs most medially along neck. Straplike. Origin: manubrium and medial end of clavical. Insertion: lower margin of body of hyoid bone. Action: acting with sternothyroid and omohyoid (all inferior to hyoid bone), depresses larynx and hyoid bone if mandible is fixed. May also flex skull.

Omohyoid

Straplike with 2 bellies. Lateral to sternohyoid. Origin: superior surface of scapula. Insertion: hyoid bone. Inferior border. acting with sternothyroid and sternohyoid (all inferior to hyoid bone), depresses larynx and hyoid bone if mandible is fixed. May also flex skull.

Platysma

Unpaired muscle. Thin, sheetlike superficial neck muscle, not strictly a head muscle. Also plays role in facial expression. Origin: fascia of chest (over pectoral muscles) and deltoid. Action: depresses mandible. Pulls lower lip back an down (i.e. produces downward sag of the mouth).

Mylohyoid

Just deep to digastric. Forms floor of mouth. Origin: medial surface of mandible. Insertion: hyoid bone and median raphe. Action: elevates hyoid bone and base of tongue during swallowing.

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