Axial Muscles (Origin, Insertion, Action)

Orbicularis oculi

O: medial margin of orbit

I: skin around eyelids

A: squint

Orbiculari oris

O: maxilla and mandible

I: lips

A: purses lips

zygomaticus major

O: zygomatic bone

I: angle of mouth

A: retracts and elevates corners of mouth

buccinator

O: maxilla and mandible

I: orbicularis oris

A: compresses cheeks

masseter

O: zygomatic arch

I: ramus of mandible

A: elevates mandible and closes jaw

occipitofrontalis

O: Frontal belly - epicranial aponeurosis

Occipital belly - occipital and temporal bones

I: Frontal belly - skin of eyebrow and bridge of nose

Occiptal belly - epicranial aponeurosis

A: Frontal belly - raises eyebrows and wrinkles forehead

Occipital belly - tenses and retracts scalp

temporalis

O: along temporal lines of skull

I: coronoid process of mandible

A: elevates mandible

sternocleidomastoid

O: clavicle and manubrium

I: mastoid region of skull

A: flexes the neck

trapezius

O: occipital bone and spinous processes of thoracic vertebrae

I: clavicle and scapula (acromion and scapular spine)

A: move scapula, elevate clavicle, or extend neck

pectoralis major

O: clavicle and sternum

I: Humerus

A: flexion and extension of the arm

pectoralis minor

O: anterior superior surface of ribs

I: coracoid process of scapula

A: depresses and protracts shoulder

serratus anterior

O: anterior and superior margins of ribs

I: anterior surface of vertebral border of scapula

A: protracts shoulder, rotates scapula

external intercostals

O: inferior border of each rib

I: superior border of more inferior rib

A: elevate ribs

internal intercostals

O: Superior border of each rib

I: Inferior border of preceding rib

A: depress ribs

diaphragm

O: xiphoid process, ribs, lumbar vertebrae

I: central tendinous sheet

A: expands thoracic cavity, compresses abdominopelvic cavity

trapezius

O: occipital bone and spinous processes of thoracic vertebrae

I: clavicle and scapula (acromion and scapular spine)

A: move scapula, elevate clavicle, or extend neck

latissimus dorsi

O: spinous process of thoracic and lumbar vertebrae

I: intertubercular groove of humerus

A: extension, adduction, and medial rotation at shoulder

rhomboid major

O: spinous process of superior thoracic vertebrae

I: vertebral border of scapula

A: adducts scapula and performs downward rotation

rhomboid minor

O: spinous process of C7-T1

I: vertebral border of scapula

A: adducts scapula and performs downward rotation

erector spinae

levator scapulae

O: transverse process of cervical vertebrae

I: vertebral border of scapula

A: elevates scapula

deltoid

O: clavicle and scapula

I: humerus

A: abduction at shoulder, flexion and rotation

supraspinatus

O: supraspinous fossa

I: greater tubercle of humerus

A: abduction at shoulder

infraspinatus

O: infraspinous fossa

I: greater tubercle of humerus

A: lateral rotation at shoulder

subscapularis

O: subscapular fossa

I: lesser tubercle of humerus

A: medial rotation at shoulder

teres minor

O: lateral border of scapula

I: greater tubercle of humerus

A: lateral rotation at shoulder

teres major

O: inferior border of scapula

I: intertubercular groove of humerus

A: adducts, extends, and medially rotates the arm