Section 2: Trunk Muscles (Thorax, Abdomen, Back)

Pectoralis Major

Flexes, adducts, medially rotates arm

Action of Pectoralis Major

Clavicle, sternum, costal cartilages

Origin of Pectoralis Major

Intertubercular sulcus of humerus

Insertion of Pectoralis Major

Pectoralis Minor

Protracts scapula

Action of Pectoralis Minor

Ribs 3-5

Origin of Pectoralis Minor

Coracoid process of scapula

Insertion of Pectoralis Minor

Rectus Abdominis

Flexes trunk, compresses abdomen

Action of Rectus Abdominis

Pubic crest and symphysis

Origin of Rectus Abdominis

Xiphoid process, ribs 5-7

Insertion of Rectus Abdominis

External Oblique

Compresses abdomen, rotates trunk

Action of External Oblique

Lower 8 ribs

Origin of External Oblique

Linea alba, iliac crest

Insertion of External Oblique

Trapezius

Elevates, retracts, rotates scapula

Action of Trapezius

Occipital bone, spines of C7-T12

Origin of Trapezius

Clavicle, acromion, spine of scapula

Insertion of Trapezius

Latissimus Dorsi

Extends, adducts, medially rotates arm

Action of Latissimus Dorsi

Spinous processes of T-7-L5, iliac crest

Origin of Latissimus Dorsi

Intertubercular sulcus of humerus

Insertion of Latissimus Dorsi

Gluteus Maximus

Extends thigh

Action of Gluteus Maximus

Ilium, sacrum, coccyx

Origin of Gluteus Maximus

Gluteal tuberosity, iliotibial tract

Insertion of Gluteus Maximus

Erector Spinae

Extends the vertebral column and the head and helps maintain upright posture

Action of Erector Spinae

posterior iliac crest

Origin of Erector Spinae

ribs, spinous processes, transverse processes of vertebrae

Insertion of Erector Spinae