Thorax Muscles

Question 1

What does Serratus posterior do?

Answer 1

Accessory Muscle of Inspiration

superior portion: elevates upper ribs, increases intrathoracic volume

Inferior portion: stabilizes lower ribs for initial contraction of diaphragm

Question 2

What does SCM do?

Answer 2

Accessory Muscle of Inspiration

Elevates sternum and upper ribs

Question 3

What do the Lats do?

Answer 3

Accessory Muscle of Inspiration

when arms fixed elevates lower ribs

Question 4

What does pec minor do?

Answer 4

Accessory Muscle of Inspiration

Elevates upper ribs; requires contraction of upper trap and levator scap to stabilize scapula

Question 5

What does pec major do?

Answer 5

Accessory Muscle of Inspiration

when arms fixed in at least 90 degrees flexion or ABD elevates middle ribs and sternum

Question 6

what does quadratus lumborum do?

Answer 6

Stabilizes lower ribs for diaphragmatic contraction during early FORCED inspiration

Question 7

What does iliocostalis thoracic and cervicis do?

Answer 7

Accessory Muscle of Inspiration

Increase intrathoracic volume by extending trunk

Question 8

What do the Abdominals do? (RA,EO,IO, TA)

Answer 8

Accessory Muscle of Expiration

Decrease intrathoracic volume by flexing trunk and depressing ribs

Compress abdominal wall and contents, increase intra-abdominal pressure -> pushes relaxed diaphragm upward decreasing intrathoracic volume

Question 9

What does Transversus Thoracis do?

Answer 9

Accessory Muscle of Expiration

Decrease intrathoracic volume by depressing the ribs and pulling them inward

Question 10

What do internal intercostals (interosseous fibers) do?

Answer 10

Accessory Muscle of Expiration

Depress ribs