Anatomy for the Figure Artist - Trunk Muscles

Sternocleidomastoid Origin

manubrium, medial third of clavicle

Sternocleidomastoid Insertion

mastoid process of skull

Sternocleidomastoid Action(s)

tilts head, rotates head, extends head

Deltoid Origin (Anterior Head)

lateral third of clavicle

Deltoid Origin (Lateral Head)

acromion process of scapula

Deltoid Origin (Posterior Head)

spine of scapula

Deltoid Insertion

halfway down the lateral humerus

Deltoid Function(s)

arm flexion, extension, ABduction

Pectoralis Major Origin

anterior medial half of clavicle, anterior surface of manubrium/sternum, cartilage of ribs 1-6

Pectoralis Major Insertion

lateral border of humerus

Pectoralis Major Action

ADduction and internal rotation of arm

Rectus Abdominus Origin

pubic symphisis

Rectus Abdominus Insertion

costal cartilages 5-7, xiphoid process of sternum

Rectus Abdominus Action

forward flexion of spine

External Oblique Origin

lower 8 ribs

External Oblique Insertion

anterior 2/3 of iliac crest, xiphoid process, anterior rectus sheath, pubis

External Oblique Action

lateral bend of spine, twists spine, forward flexion (when both sides flex)

Serratus Anterior Origin

ribs 1-8/9 in an arc around the shoulder

Serratus Anterior Insertion

anterior scapula

Serratus Anterior Action

scapula rotation (reach up), protraction of scapula (forward and around)

Trapezius Origin (upper)

base of skull along nuchal ligament and C7

Trapezius Origin (middle)

spinous processes T1-5

Trapezius Origin (Lower)

Spinous Processes T6-12

Trapezius Insertion

spine of scapula, acromion process, clavicles

Trapezius Action

lifts, retracts, lowers scapula, ABducts head sideways, extends neck to bring backwards

Infraspinatus Origin

posterior surface of scapula below spine

Infraspinatus Insertion

greater tuberosity of the humerus, posterior side

Infraspinatus Action

lateral rotation of arm

Teres Major Origin

1/3rd of bottom of posterior scapula

Teres Major Insertion

lower portion of anterior facing humerus

Teres Major Action

ADducts, extends, and internally rotates arm

Latissimus Dorsi Origin

sacrum, posterior third of iliac crest, all lumbar vertebrae, lower 6 thoracic vertebrae, lower 3 ribs

Latissimus Dorsi Insertion

bicipital groove of anterior side humerus

Latissimus Dorsi Action

adduction and extension of arm, medial rotation of trunk