Thoracic muscles O, I, N, A

Question 1

Pectoralis major

Answer 1

O: Clavicular head on anterior surface of medial half of clavicle
Sternocostal head on anterior surface of sternum, superior 6 costal cartilages and aponeurosis of external oblique

I: Lateral lip of intertubercular sulcus of humerus

N: Lateral and medial pectoral nerves

A: adducts and medially rotates humerus; draws scapula anteriorly and inferiorly

Question 2

Pectoralis minor

Answer 2

O: 3rd - 5th ribs near costal cartilages

I: Medial boarder and superior surface of coracoid process of scapula

N: Medial pectoral nerve (C8, T1)

A: Stabilizes scapula by drawing it inferiorly and anteriorly against thoracic wall

Question 3

Serratus anterior

Answer 3

O: External surfaces of lateral parts of 1st - 8th ribs

I: Anterior surface of medial boarder of scapula (including superior and inferior angles

N: Long thoracic nerve (C5-C7)

A: Protracts scapula and holds it against thoracic wall; rotates scapula

Question 4

Anterior scalene

Answer 4

O: Transverse processes of C3-C6

I: 1st rib

N: Cervical spinal nerves (C4-C6)

A: Flexes neck laterally; elevates 1st rib during forced inspiration

Question 5

Middle scalene

Answer 5

O: Posterior tubercles of transverse processes of C2-C7

I: Superior surface of 1st rib (posterior to groove for subclavian artery

N: Anterior rami of cervical spinal nerves

A: Flexes neck laterally; elevates 1st rib during forced inspiration

Question 6

Posterior scalene

Answer 6

O: Posterior tubercles of transverse processes of C5-C7

I: External boarder of 2nd rib

N: Anterior rami of cervical spinal nerves C7 and C8

A: Flexes neck laterally; elevates 2nd rib during forced inspiration

Question 7

Serratus Posterior Superior

Answer 7

O: Spinous process of C7 - T3

I: Superior boarders of 2nd - 4th ribs

N: 2nd - 5th intercostal nerves

A: Elevates superior 4 ribs

Question 8

Serratus Posterior Inferior

Answer 8

O: Spinous processes of T11- L2

I: Inferior boarders of 8th - 12th ribs near their angles

N: Anterior rami to T9 - T12 thoracic spinal nerves

A: Depresses inferior ribs

Question 9

Levatores Costarum

Answer 9

O: Transverse processes of C7 - T11

I: Subjacent ribs between tubercle and angle

N: Posterior primary rami of C8 -T11 nerves

A: Elevates ribs

Question 10

External Intercostal

Answer 10

O: Inferior boarder of ribs

I: Superior boarder of ribs below

N: Intercostal nerve

A: Elevates ribs during forced INSPIRATION

Question 11

Internal Intercostal

Answer 11

O: Inferior boarder of ribs

I: Superior boarder of ribs below

N: Intercostal nerve

A: Depresses ribs during EXPIRATION

Question 12

Innermost Intercostal

Answer 12

O: Inferior boarder of ribs

I: Superior boarder of ribs below

N: Intercostal nerve

A: elevates ribs

Question 13

Subcostal (T7 - T12)

Answer 13

O: Internal surface of lower ribs near their angles

I: Superior boarder of 2nd rib below origin

N: Intercostal nerve

A: Probably acts in same manner as internal intercostal muscles

Question 14

Transverse Thoracis

Answer 14

O: Posterior surface of lower sternum

I: Internal surface of costal cartilages 2 - 6

N: Intercostal nerve

A: Weakly depresses ribs

Question 15

Rhomboid Major

Answer 15

O: Spinous process of T2 - T5

I: Medial boarder of scapula from level of spine to inferior angle

N: Dorsal scapular nerve (C4, C5)

A: Retract scapula and rotate its glenoid cavity inferiorly

Question 16

Rhomboid Minor

Answer 16

O: Spinous processes of C7 and T1

I: Smooth triangular area at medial end of scapular spine

N: Dorsal scapular nerve (C4, C5)

A: Retract scapula and rotate its glenoid cavity inferiorly