1. Notes: Mechanics of Ventilation (pg 8)

2. Notes: Mechanics of Ventilation (pg 8)
• Pulmonary ventilation = Breathing. Inspiration
(Inhale) and Expiration (Exhale)

3. Notes: Mechanics of Ventilation (pg 8)
• Pulmonary ventilation = Breathing. Inspiration
(Inhale) and Expiration (Exhale)
• You do not suck air into your lungs. Instead,
you increase the volume of your chest cavity,
which decreases the pressure, and air flows in
on its own

4. Boyle’s Law
• When the volume of a gas increases, the
pressure decreases. When volume
decreases, pressure increases.

5. Boyle’s Law
• When the volume of a gas increases, the
pressure decreases. When volume
decreases, pressure increases.
• P1V1 = P2V2

6. Boyle’s Law
• When the volume of a gas increases, the
pressure decreases. When volume
decreases, pressure increases.
• P1V1 = P2V2
• Air naturally flows from areas of high pressure
to areas of low pressure

7. Output (pg 9)
Practice Problem (write out the problem)
• A gas has a volume of 3.0 liters and a pressure
of 2.0 atm. The volume is increased to 4.0
liters. What is the new pressure?
• Show your work, including writing out the
formula!

8. Muscles involved in Ventilation (pg 8)
• Diaphragm = Dome-shaped muscular “shelf”
separating the thoracic cavity from the
abdominal cavity. Lungs rest on it.

9. Muscles involved in Ventilation (pg 8)
• Diaphragm = Dome-shaped muscular “shelf”
separating the thoracic cavity from the
abdominal cavity. Lungs rest on it.
• Intercostal muscles = Located between the
ribs

10. Inspiration
• Diaphragm contracts, causing it to drop and
flatten. This increases the volume of the
thoracic cavity.

11. Inspiration
• Diaphragm contracts, causing it to drop and
flatten. This increases the volume of the
thoracic cavity.
• During labored breathing, the external
intercostal muscles also contract, elevating the
ribs and further increasing the thoracic
volume.

12. Inspiration
• Diaphragm contracts, causing it to drop and
flatten. This increases the volume of the
thoracic cavity.
• During labored breathing, the external
intercostal muscles also contract, elevating the
ribs and further increasing the thoracic
volume.
• As the volume increases, the pressure inside
the lungs decreases and air flows in.

13. Expiration
• Diaphragm relaxes and rises, decreasing
thoracic volume

14. Expiration
• Diaphragm relaxes and rises, decreasing
thoracic volume
• In forceful expiration, internal intercostal
muscles contract, pulling the ribs down

15. Expiration
• Diaphragm relaxes and rises, decreasing
thoracic volume
• In forceful expiration, internal intercostal
muscles contract, pulling the ribs down
• As volume decreases, pressure increases and
air flows out of the lungs

16. Output (pg 9)
• Sketch two upper bodies and label one
“inspiration” and the other “expiration”
• Draw in the relative positions of the
diaphragm,intercostal muscles, and ribs

17. Activity (record results on page 9)
• Work in your lab table groups
• Sculpt a diaphragm and place in on your
skeleton. Put it in the expiration position.
• Measure the volume of the thoracic cavity in
cubic centimeters
• Move the diaphragm into the inspiration
position. Measure the new volume.
• Assuming that the pressure inside the lungs
during expiration is 1 atm, calculate the
pressure during inspiration