Anatomy of Respiration

Question 1

What are the 3 primary muscles of inspiration?

Answer 1

1. diaphragm
2. external intercostals (elevate ribs)
3. interchondral part of intercostals (elevate ribs)

Question 2

What are the 4 accessory muscles of forced inspiration?

Answer 2

1. SCM (elevates sternum)
2. Scalenes (elevate ribs)
3. Pec minor (elevates ribs)
4. Serratus anterior (expands rib cage laterally)

Question 3

What are the muscles of quiet expiration?

Answer 3

None - it is a passive process due to lung elasticity following relaxation of inspiratory muscles

Question 4

What are the muscles of forced expiration?

Answer 4

1. Intercostal part of internal intercostals (lower the ribs)
2. Abdominals (obliques, rectus, transverse)
   - compress abdominal contents and push up diaphragm
3. Transverse thoracis (compresses rib cage)

Question 5

Which intercostal muscles are active during inspiration?

Answer 5

1. External intercostals (elevate ribs)

2. Interchondral part of internal intercostals (elevate ribs)

Question 6

Which intercostal muscles are active during forced expiration?

Answer 6

Intercostal part of internal intercostals (depress ribs)