11. Scapula Flashcards
Trapezius
Origin
Insertion
Action
Most superficial muscle of the posterior thoracic, flat and triangular; upper fibers run inferiorly to scapula; middle fibers run horizontally to scapula; lower fibers run superiorly to scapula
O- occipital bone, ligamentum nuchae, spine of C and thoracic vertebrae
I- a continuous insertion along acromion and spine of scapula and lateral third of clavicle
A-stabilizes, elevates,retracts and rotates scapula. Middle fibers retract (adduct) scapula (shrugging shoulders) or can help extend head when scapula is fixed; inferior fibers depress scapula and shoulder
Levator scapulae
Origin
Insertion
Action
Located at back and side of neck, deep to trapezius; thick, straplike muscle
O- transverse processes of c1-c4
I- medial border of the scapula, superior to the spine
A- elevates and adducts scapula in synergy w/superior fibers of trapezius, rotate scapulae downward; when scapula is fixed, flexes neck to same side
Rhomboid major
Origin
Insertion
Action
Two rectangular muscles lying deep to trapezius and inferior to levator scapulae; inferior muscle
O- spinous processes of T2 - T3
I- medial border of scapula
A- stabilizes scapula, act together (w/middle trapezius fibers) to retract scapula, thus squaring shoulders - rotate scapulae downward - when arm is lowered against resistance - paddling a canoe
Rhomboid minor
Origin
Insertion
Action
Two rectangular muscles lying deep to trapezius and inferior to levator scapulae; superior muscle
O- spinous processes of C7 & T1
I- medial border of scapula
A- stabilizes scapula, act together (w/middle trapezius fibers) to retract scapula, thus squaring shoulders - rotate scapulae downward - when arm is lowered against resistance - paddling a canoe
Serratus anterior
Origin
Insertion
Action
Fan shaped muscle; lies deep to scapula, deep and inferior to pectoral muscles on lateral rib cafe, forms medial wall of axilla; origins have serrated or sawtooth appearance
O- series of muscle slips from ribs 1-8 or 9
I- entire anterior surface of vertebral border of scapula
A- rotates scapula upward; prime mover to protract and hold scapula against chest wall; important role in abduction and raising of arm and in horizontal arm movements (pushing, punching) called “boxers muscle”
Pectoralis minor
Origin
Insertion
Action
Flat thin muscle deep to pectoralis major
O- anterior surfaces of ribs 3-5 or 2-4
I- coracoid process of scapula
A- with ribs fixed, protracts and rotates scapula downward, with scapula diced, draws rib cage superiorly
