Muscles Of The Thorax That Move The Pectoral Girdle

Question 1

Subclavius

Anterior thoracic muscle

Answer 1

O- First rib & cartilage

I- Inferior surface of middle 1/3 clavicle

A-Depress the clavicle and draw it anteriorly
Elevate first rib [to assist during inhalation]
Stabilize the sternoclavicular joint

N-Subclavian C5, 6

Question 2

Pectoralis minor

Anterior thoracic muscles

Answer 2

O-Third, fourth and fifth ribs

I-Medial surface of coracoid process of the scapula

A-Depress the scapula [scapulothoracic joint]
Abduct the scapula [S/T joint]
Downwardly rotate the scapula
With the scapula fixed: assist to elevate the thorax during forced inhalation

N-Medial pectoral, with fibers from a communicating branch of the lateral pectoral C [6], 7, 8, T1

Question 3

Serratus anterior

Anterior thoracic muscles

Answer 3

O- External surfaces of upper eight or nine ribs

I-Anterior surface of medial border of the scapula

A-With the origin fixed: Abduct the scapula [scapulothoracic joint]
Upwardly rotate the scapula [S/T joint]
Depress the scapula [S/T joint]
Hold the medial border of the scapula against the rib cage
With the scapula fixed: May act to elevate the thorax during forced inhalation

N-Long thoracic C-5, 6, 7, 8

Question 4

Trapezius

Posterior thoracic muscles

Answer 4

O-External occipital protuberance, medial portion of the superior nuchal line of the occiput, Ligamentum nuchae and spinous processes of C7 through T12

I-Lateral 1/3 of clavicle, acromion and spine of the scapula

A-Upper fibers:
Bilaterally: Extend the head and neck
Unilaterally: laterally flexed the head and neck to the same side
Rotate the head and neck to the opposite side
Elevate scapula [scapulothoracic joint] upwardly rotate the scapula [S/T joint]
Middle fibers: Adduct the scapula [S/T joint]
Stabilize the scapula [S/T joint]
Lower fibers: Depress the scapula [S/T joint]
Upwardly rotating scapula [S/T joint]

N-Spinal portion of cranial nerve XI [accessory] and ventral ramus C2,3,4

Question 5

Levator scapulae

Posterior thoracic muscles

Answer 5

O-Transverse processes of first through fourth cervical vertebrae

I-Medial border of scapula, between superior angle and superior portion of spine of scapula

A-Unilaterally: elevate the scapula [S/T joint]
Downwardly rotate the scapula [S/T joint]
Laterally flexed to head and neck
Rotate the head and neck to the same side
Bilaterally: extend the head and neck

N-Cervical 3, 4, and dorsal scapular C4, 5

Question 6

Rhomboid major

Posterior thoracic muscle

Answer 6

O-Spinous processes of T2 to T5

I-Medial border of the scapula between spine of the scapula and inferior angle

A-Adduct the scapula [scapulothoracic joint]
[S/T joint]
Downwardly rotate the scapula [S/T joint]

N-Dorsal scapular C4, 5

Question 7

Rhomboid minor

Posterior thoracic muscles

Answer 7

O-spinous processes of C7 and T1

I-Upper portion of medial border of the scapula, at the level of the spine of the scapula

A-Adduct the scapula [S/T joint]

N-Dorsal scapular C4, 5