Download Thoracic Muscles

Origin and Insertion
Ms. Treto
Thoracic Muscles
Trapezius
 Origin – occipital bone/spinous processes of c7 – T12.
 Insertion – acromion/spine of
scapula; lateral 1/3 of scapula.
 Action – stabilizes/elevates/
retracts/ rotates scapula
Latissimus Dorsi
 Origin –spinous processes of T7 – L5,
iliac crest, ribs, and inferior angle
of scapula
 Insertion – intertubercle groove of
humerus
 Action – adducts, extends and
internally rotates the arm. Also, a
very powerful rotator of the trunk.
Infraspinatus
 Origin – infraspinous fossa of the
scapula
 Insertion – greater tubercle of the
humerus
 Action – lateral rotation of the arm
and stabilizes the humerus
Rhomboid Major and Minor
 Major action – retracts the scapula
and rotates it to depress the glenoid
cavity.
 Minor action – retracts and rotates
scapula
Sternocleidomastoid
 Origin – manubrium and medial
portion of the clavicle
 Insertion – mastoid process
of the temporal bone
 Action – 1. Unilaterally –
cervical rotation and lateral
flexion. 2. Bilaterally – cervical
flexion and raises the sternum
Pectoralis Major
 Origin –Clavicle, sternum and upper ribs
 Insertion – greater tubercle
on humerus
 Action – 1. adduction of
humerus. 2. flexion and
extension of humerus.
Rectus Abdominis
 Origin – crest of pubis
 Insertion – costal cartilage of
ribs 5 – 7, xiphoid process
of sternum
 Action – flexion of the
lumbar spine
External Obliques
 Origin – Ribs 5 - 12
 Insertion – Iliac crest
 Action – Contralateral rotation
of torso