1. Muscles of Ventilation
Ventilation is the movement of air into and
out of the lungs.
Respiration is the cellular process of
breaking down chemical energy (substrates)
to make ATP
C6H12O6 + 6 O2 6 CO2 + 6 H20 + E

2. Ventilation
• Inspiration (Inhalation): active process.
– Requires muscular action
– Change in thoracic volume change in
pressure. (Boyle’s Law)
• Change in pressure drives air into lungs
• Expiration (exhalation): passive process
– Occurs when muscles of breathing relax
– Forced exhalation: muscular activity required

3. Resting Ventilation
• Two muscles of resting ventilation
• Diaphragm
– Origin: Xiphoid, ribs 7-12 and their costal
cartilage, anterior surface of lumbar vertebrae.
– Insertion: Central tendinous sheet
– Action: expand thoracic cavity, compresses
abdominopelvic cavity
• Intrathoracic pressure and valsalva’s

5. Resting Ventilation
• External intercostals
– Origin: Inferior border of each rib
– Insertion: Superior border of the
more inferior rib
(the rib below the superior one)
• Action: Lifts the lower rib to
expand the thoracic cavity

6. Resting Exhalation
• This is a passive process in which the
diaphragm and external intercostals relax and
the thoracic cavity recoils back to its resting
volume (gets smaller) forcing air from the
lungs due to the increase in intrathoracic
pressure.

7. Muscles of Inspiration during Exercise
• These muscles lift the clavicle and ribs
• These are known as Accessory Inspiratory
muscles. These muscles (SCM, scalene, traps).
Others to follow
• SCM: O and I will reverse in this case.
• Scalene: Work in conjunction with SCM
– O: Transverse processes of C2 – C7
– I: First two ribs
• Ant. and Middle scalene lift rib 1
• Post. Scalene lifts rib 2

8. Muscles of Inspiration during Exercise
SCM: O and I will reverse in this case.
Scalene: Work in conjunction with SCM
O: Transverse processes of C2 – C7
I: First two ribs
•Ant. and Middle scalene lift rib 1
•Post. Scalene lifts rib 2

11. Muscles of Inspiration during Exercise
• Diaphragm
• External intercostals – raises the ribs
– Other Accessory Muscles
• Trapezius (upper fibers) – raises the clavicle
• Serratus anterior – raises the ribs
• Pec minor – raises ribs when scapula is fixed

12. Expiratory Muscles during Exercise
• Relaxation of diaphragm
• Abdominal muscles
• Internal intercostals

13. External Oblique
• Origin
– Lateral side of ribs 5-12
• Insertion
– Anterior iliac crest, pubic
crest
• Location:
– Lateral/Anterior
• Movements
– Flexion (together)
– Ipsilateral flexion
– Contralateral rotation
(independently)

14. Internal Oblique
• Origin
– Anterior iliac crest
• Insertion
– Cartilage of ribs 8-10
• Location:
anterior/medial
• Movements (LS)
– Flexion
– Ipsilateral flexion
Fiber direction

15. Rectus Abdominis
• Origin
– Pubic crest
• Insertion
– Cartilage of ribs 5-
7, xiphoid process
• Location: anterior
• Movements
– Trunk flexion