Thorax Muscles

Question 1

external intercostals (superior attachment)

Answer 1

inferior margin of rib above

Question 2

external intercostals (inferior attachment)

Answer 2

superior margin of rib below

Question 3

external intercostals (action)

Answer 3

stabilizes rib cage; active during inspiration; supports intercostal space; when first rib is fixed, it pulls ribs superiorly to increase anteroposterior and lateral diameter

Question 4

internal intercostals (superior attachment)

Answer 4

lateral edge of costal groove of rib above

Question 5

internal intercostals (inferior attachment)

Answer 5

superior margin of rib below deep to attachment of related external intercostals

Question 6

internal intercostals (action)

Answer 6

stabilizes rib cage; active during expiration; when lower ribs are fixed by abdominal muscles, lowers ribs during expiration

Question 7

innermost intercostals (superior attachment)

Answer 7

medial edge of costal groove of rib above

Question 8

innermost intercostals (inferior attachment)

Answer 8

internal aspect of superior margin of rib below

Question 9

innermost intercostals (action)

Answer 9

assists internal and external intercostal muscles

Question 10

subcostales (superior attachment)

Answer 10

internal surface (near angle) of lower ribs

Question 11

subcostales (inferior attachment)

Answer 11

internal surface of second or third rib below

Question 12

subcostales (action)

Answer 12

may depress ribs

Question 13

transversus thoracis (superior attachment)

Answer 13

inferior margin and internal surfaces of costal cartilages of ribs 2-6

Question 14

transversus thoracis (inferior attachment)

Answer 14

inferior aspect and deep surface of body of sternum, xiphoid process, and costal cartilages of ribs 4-7

Question 15

transversus thoracis (action)

Answer 15

depresses costal cartilages; lies deep to internal thoracic vessels and secures these to the wall

Question 16

diaphragm (origin)

Answer 16

xiphoid process, lower six costal cartilages, first three lumbar vertebrae

Question 17

diaphragm (insertion)

Answer 17

central tendon

Question 18

diaphragm (nerve)

Answer 18

phrenic nerve (C3, C4, C5)

Question 19

diaphragm (action)

Answer 19

most important muscle of inspiration; increases vertical diameter of thorax by pulling central tendon downwards; assists in raising lower ribs; used in abdominal straining and weightlifting

Question 20

Explain inspiration.

Answer 20

scaleni muscle fixes first rib and intercostal muscles raise second to twelvth ribs towards first rib

Question 21

Explain expiration.

Answer 21

quadratus lumborum and oblique muscle of abdomen fix twelvth rib and intercostal muscle depress first to eleventh ribs towards twelvth rib

Question 22

levatores costatorum (origin)

Answer 22

tip of transverse processes of C7 to T11

Question 23

levatores costatorum (insertion)

Answer 23

rib below vertebra of origin, near tubercle

Question 24

levatores costatorum (nerve)

Answer 24

posterior rami of thoracic spinal nerves

Question 25

levatores costatorum (action)

Answer 25

raises ribs

Question 26

serratus posterior superior (origin)

Answer 26

lower part of ligamentum nuchae, spines of C7 to T11, and supraspinous ligament

Question 27

serratus posterior superior (insertion)

Answer 27

upper border of ribs 2-5 (lateral to angle)

Question 28

serratus posterior superior (innervation)

Answer 28

anterior rami of spinal nerves T2-T5

Question 29

serratus posterior superior (action)

Answer 29

elevates ribs 2-5

Question 30

serratus posterior inferior (origin)

Answer 30

spines of T11-L3 and supraspinous ligament

Question 31

serratus posterior inferior (insertion)

Answer 31

lower border of ribs 9-12 (lateral to angles)

Question 32

serratus posterior inferior (innervation)

Answer 32

anterior rami of spinal nerves T9-T12

Question 33

serratus posterior inferior (action)

Answer 33

expiratory muscle (depresses ribs)