BIOLN261 - Chapter 10 Major Muscles of the Axial Skeleton

Innervation

Supply of motor nerves in skeletal muscles/muscle supply

Epicranius

Contains 2 muscles

What are the 2 muscles in the epicranius?

2 Galea Aponeurotica

What is the job of the epicranius?

2 muscles pull the scalp forwards and backwards

Frontalis

Covers the forehead/dome of the skull

Origin of the frontalis

Galea Aponeurotica (of the epicranius)

Insertion of the frontalis

skin of eyebrow/root of nose

What is the job of the frontalis (if it were alone?)

Wrinkles the forehead skin to frown

What is the job of the frontalis with another muscle?

Raise the eyebrow

What other muscle helps raise the eyebrows with the frontalis?

Occipitalis

Occipitalis

back of the head (sorta)

Origin of the occipitalis 2 places it inserts

occipital/temporal (mastoid) bone

Insertion of occipitalis

galea aponeurotica

Function of occipitalis

pulls the scalp posteriorly to help raise the eyebrow

Orbicularis Oculi

Thin, flat muscle of the eyelid surrounding the rim of the orbit

Origin of the orbicularis Oculi

Frontal/maxillary bone

Insertion of the Orbicularis Oculi

Tissue of the eyelid (forms a circle)

Function of Orbicularis Oculi

Closes the eye

Zygomaticus

muscle pair from cheekbone to corner of mouth

Origin of zygomaticus

zygomatic bone

Insertion of Zygomaticus

Skin/muscles at corner of mouth

Function of zygomaticus

Raise mouth upwards

Risorius

inferior and lateral to zygomaticus

origin of risorius

lateral fascia associated with masseter muscle

insertion of risorus

skin at angle of mouth

Function of risorius

draws corner of lip laterally

Levator Labii Superioris

between orbucularis oris and inferior eye (orbicularis oculi)

Origin of Levator labii superioris

zygomatic bone/infraorbital margin of maxilla

Insertion of levator labii superioris

Skin and Muscle of UPper Lip

Function of Levator Labii Superioris

Opens the lip, furrow the upper lip

Depressor Labii Inferioris

Small muscle running from mandible to lower lip

Origin of Depressor Labii Inferioris

Body of mandible

Insertion of Depressor Labii Inferioris

Muscle of Lower lip

Function of Depressor Labii Inferioris

draws lower lip inferiorly (pout)

Origin of Orbicularis Oris

arises indirectly from maxilla/mandible (in a circle)

Function of orbicularis oris

closes/purses lips (when kissing or whistling)

Mentalis

V shape on Chin

Origin of Mentalis

Mandible below incisors

Insertion

Skin of Chin

Function of Mentalis

Wrinkles chin when pouting

Buccinator

thin, horizontal cheek muscle

Origin of buccinator

molar region of maxilla/mandible

Insertion of buccinator

orbicularis oris

Function of buccinator

Compresses the cheek (help to play woodwind instruments and hold food between teeth while chewing)

Platysma

sheet like muscle that’s superficial in the neck

origin of Platysma

fascia of chest muscle

Insertion of Platysma

Lower margin of mandible

Function of platysma

Depress the mandible, pull lower lip down

Origin of Masseter

Zygomatic arch (zygomatic bone) —> sits laterally

Insertion of masseter

ramus of mandible

Function of masseter

Moves when jaw closes (elevates the mandible)

Temporalis

Fan shaped

What bones does the temporalis cover?

Temporal, frontal, parietal

Insertion of Temporalis

Coronoid process of mandible

Function of Temporalis

Closes the jaw, elevates, retracts, and maintains the position of the mandible at rest

3 tongue muscles

Genioglossus, hypoglossus, styloglossus

What are the 4 Suprahyoid Muscles?

Digastric, Stylohyoid, Mylohyoid, Geniohyoid

Digastric

2 bellies, pass through tendon on the hyoid muscle

Origin of Digastric (anterior belly)

mandible

Origin of Digastric (posterior belly)

Mastoid process of Temporal Bone

Where does the digastric muscle insert?

connective tissue loop to hyoid bone

Function of Digastric Muscle

Opens the Mouth and Depresses the mandible

Stylohoid

parallel posterior belly of digastric muscle

Origin of Stylohoid

Origin at styloid process of temporal bone

Insertion of Stylohoid bone

Inserts at the Hyoid Bone

Function of Stylohoid bone

elevates and retracts hyoid

MyloHyoid

Triangular muscle

Origin of Mylohyoid

Origin at Medial Surface of mandible

Insertion of Mylohyoid

Inserts at Hyoid Bone (and median raphe)

Function of Mylohyoid

Elevates the hyoid bone and floor of mouth, forcing food bolus into pharync

3 Infrahyoid Muscles

Sternohyoid, Sternothyroid, Omohyoid

Sternohyoid

Most median muscle of the neck

Origin of Sternohyoid

Origin at manubrium of sternum/medial end of clavicle

Insertion of Sternohyoid

Inserts at lower margin of hyoid bone

Function of Sternohyoid

Depress larynx/hyoid bone

Sternothyroid

Lateral/deep to sternohyoid

Origin of sternothyroid

Origin at posterior surface of manubrium

Insertion of sternothyroid

Inserts at thyroid cartilage

Function of Sternothyroid

pulls larynx/hyoid bone inferiorly (down)

Omohyoid 

strap muscle with 2 bellies

Origin of Omohyoid

Origin at superior surface of scapula

Insertion of omohyoid

hyoid bone (lower border)

Function of omohyoid

depresses and retracts the hyoid bone

Innervation of masseter

N V (trigerminal nerve)

Anterolateral neck muscles (2)

Sternocleidomastoid and scalenes

Sternocleidomastoid

2 headed muscle deep to platysma

Origin of sternocleidomastoid

origin at manubrium of sternum/medial portion of clavicle

Insertion of Sternocleidomastoid

inserts at mastoid process of temporal bone

Function of sternocleidomastoid

Flex/laterally rotate head (right sternocleidomastoid flexes when turning to the left)

Scalenes

Lateral on neck

Origin of Scalenes

Origin at Transverse processes of cervical vertebraes

Insertion of Scalenes

Inserts anterolaterally on first 2 ribs

Function of Scalenes

Elevate the first 2 ribs

Origin of Splenius

Origin of Spinous processes of C7-T6

Insertion of Splenius

Inserts at Mastoid process of temporal bone/occipital bone

Function of Splenius

Extend/hyperextend neck

What is the job of erector spinae?

Hold you up, have good posture

Origin of Semispinalis

Transverse processes of C7 to T12

Insertion of Semispinalis (3 insertions)

Insertion at Occipital bone, spinous process of cervical, and thoracic vertebrae T1-4

Quadratus Lumborum

Fleshy muscle forming part of posterior abominal wall