Muscles of the Thoracic Wall

Question 1

Pectoralis major

Answer 1

Proximal attachment: clavicle, sternum, upper 6 costal cartilages
Distal attachment: lateral lip of the intertubercular groove
Innervation: medial and lateral pectoral nerves
Blood supply: pectoral branches of thoracoacromial trunk

Question 2

Pectoralis minor

Answer 2

Proximal attachment: ribs 3 -5
Distal attachment: coracoid process
Innervation: medial pectoral nerve
Blood supply: pectoral branches of thoracoacromial trunk

Question 3

Serratus anterior

Answer 3

Proximal attachment: upper 8 - 9 ribs
Distal attachment: medial border of scapula
Innervation: long thoracic nerve
Blood supply: lateral thoracic artery

Question 4

Serratus posterior superior

Answer 4

Action: elevates

Question 5

Serratus posterior inferior

Answer 5

Action: depresses

Question 6

Levator costarum

Answer 6

12 pairs of fan-shaped muscles

Transverse processes C7 - C11 to costal tubercle and costal angle

Question 7

External intercostal muscles

Answer 7

Elevates
Fibers run anteroinferiorly from upper rib to lower rib
Origin: costal tubercle
Insertion: costochondral junction
Extends to sternum as external (anterior) intercostal membrane

Question 8

Internal intercostal muscles

Answer 8

Costal portion: elevates
Chondral portion: depresses
Fibers run posteroinferiorly from upper rib to lower rib
Origin: lateral border of sternum
Insertion: costal angle
Extends to vertebrae as internal (posterior) intercostal membrane

Question 9

Innermost intercostal muscles

Answer 9

Elevate
Located in third muscular layer of intercostal space
Found internally on posterolateral thoracic wall

Question 10

Transversus thoracis

Answer 10

Depresses ribs
Lower sternum to the internal surface of 2nd - 6th costal cartilages
Located in third muscular layer of intercostal space
Found anteriorly

Question 11

Thoracic diaphragm

Answer 11

Sternal, costochondral, and lumbar attachments

80% of quite breathing