Thoracic Muscles

Question 1

External intercostals

Answer 1

PA: inferior border of rib

DA: superior border of next rib

*fibers run superior-lateral to inferior-medial (down and in)

A: elevation of ribs

Intercostal Nerve Innervation (segmental)

Question 2

Internal & Innermost Intercostals

Answer 2

PA: inferior border of rib

DA: superior border of next rib

*fibers run superior-medial to inferior-lateral (down and out)

A: depression of ribs

Intercostal Nerve Innervation (segmental)

Question 3

Transversus thoracis

Answer 3

PA: posterior sternum

DA: costal cartilages

A: depress ribs

Intercostal Nerve Innervation (segmental)

Question 4

Diaphragm

Answer 4

PA: xiphoid process, inner surface of lower ribs & costal cartilages, & lumbar vertebrae via the crura

DA: central tendon

A: inspiration (negative thoracic pressure by inferior displacement)

Phrenic Nerve innervation (C3-C5)