Muscle Origins, Insertions, Actions - Trunk

Front 1

Teres minor

Back 1

Origin: middle half of the scapula’s lateral margin
Insertion: lowest of three facets of the greater tubercle of humerus
Action:
lateral rotation of the humerus
stabilizes the glenohumeral joint

Front 2

Teres major

Back 2

Origin: inferior, lateral margin of the scapula
Insertion: crest of lesser tubercle (just medial to the insertion of latissimus dorsi)
Action:
assists in adduction of arm
assists in medial rotation of arm
assists in extension from an flexed position

Front 3

Subscapularis

Back 3

Origin: subscapular fossa
Insertion: lesser tubercle of humerus
Action:
medial rotation of the humerus
stabilizes the glenohumeral joint

Front 4

Splenius capitis

Back 4

Origin:
lower portion of ligamentum nuchae
spinous processes of C3-T3(4)
Insertion:
superior nuchal line
mastoid process of temporal bone
Action:
bilateral contraction: extend head & neck
unilateral contraction: rotate and laterally bend head & neck to the contracted (same) side

Front 5

Splenius cervicis

Back 5

Origin: spinous process of T3-T6
Insertion: posterior tubercles of transverse processes of C2-C4
Action:
bilateral contraction: extend head & neck
unilateral contraction: rotate and laterally bend head & neck to the contracted (same) side

Front 6

Trapezius

Back 6

Origin:
external occipital protuberance
along the medial sides of the superior nuchal line
ligamentum nuchae (surrounding the cervical spinous processes)
spinous processes of C1-T12
Insertion:
posterior, lateral 1/3 of clavicle
acromion
superior spine of scapula
Action:
elevates scapula
upward rotation of the scapula (upper fibers)
downward rotation of the scapula (lower fibers)
retracts scapula

Front 7

Latissimus dorsi

Back 7

Origin:
spinous process of T7-L5
upper 2-3 sacral segments
iliac crest
lower 3 or 4 Ribs
Insertion: lateral lip of the intertubercular groove
Action:
adduction of humerus
medial rotation of the humerus
extension from flexed position
downward rotation of the scapula

Front 8

Subclavius

Back 8

Origin: first rib about the junction of bone and cartilage
Insertion: lower surface of clavicle
Action: assists in stabilizing the clavicle

Front 9

Pectoralis major

Back 9

Origin:
medial 1/3 of clavicle
anterior aspect of manubrium & length of body of sternum
cartilaginous attachments of upper 6 ribs
external oblique's aponeurosis
Insertion:
lateral lip of bicipital groove to the crest of the greater tubercle
clavicular fibers insert more distally; sternal fibers more proximally
Action:
adducts humerus
medially rotates humerus
flexion of the arm from extension (clavicular portion)

Front 10

Pectoralis minor

Back 10

Origin: outer surface of ribs 2-5 or 3-5 or 6
Insertion: medial aspect of coracoid process of the scapula
Action:
depresses & downwardly rotates the scapula
assists in scapular protraction from a retracted position
stabilizes the scapula

Front 11

Levator scapulae

Back 11

Origin: transverse processes of C1-C3 or C4
Insertion: superior angle of scapula toward the scapular spine
Action:
elevates the scapula
extends and/or laterally flexes the head

Front 12

Rhomboid minor

Back 12

Origin:
spinous process of C7 & T1
ligamentum nuchae
supraspinous ligament
Insertion: medial margin of the scapula at the medial angle
Action: retract scapula

Front 13

Rhomboid major

Back 13

Origin:
spinous processes of T2-T5
supraspinous ligament
Insertion: medial scapula from the scapular spine to the inferior angle
Action: retract scapula

Front 14

Serratus anterior

Back 14

Origin: fleshy slips from the outer surface of upper 8 or 9 ribs
Insertion: costal aspect of medial margin of the scapula
Action:
protract scapula
stabilize scapula
assists in upward rotation

Front 15

Deltoid

Back 15

Origin:
lateral, anterior 1/3 of distal clavicle
lateral boarder of the acromion
scapular spine
Insertion: deltoid tuberosity of humerus
Action:
abducts arm
flexion and medial rotation (anterior portion)
extension and lateral rotation (posterior portion)

Front 16

Supraspinatus

Back 16

Origin:
supraspinous fossa
muscle fascia
Insertion: uppermost of three facets of the greater tubercle of humerus
Action:
abduction of arm (first 15-20°)
stabilizes glenohumeral joint

Front 17

Infraspinatus

Back 17

Origin:
infraspinous fossa
muscle fascia
Insertion: middle facet of greater tubercle of humerus
Action:
external rotation of the humerus
stabilizes the glenohumeral joint