1. Events of Respiration
Pages

2. The Respiratory Membrane: Events and Players
Gas exchange occurs via diffusion
Oxygen enters the blood
Carbon dioxide enters the alveoli
Alveolar macrophages (“dust cells”) protect:
pick up bacteria, carbon particles, and other debris
Surfactant (a lipid-protein molecule) coats gas-exposed alveolar surfaces to prevent “sticking” and collapse during expiration
© 2015 Pearson Education, Inc.

3. Figure 13.6 Anatomy of the respiratory membrane (air-blood barrier).
Red blood cell
Capillary
Endothelial cell
nucleus
Alveolar pores O2
Capillary
CO2
Macrophage
Alveolus
Nucleus of
squamous
epithelial cell
Respiratory
membrane
Alveolar epithelium
Fused basement
membranes
Capillary endothelium
Alveoli (gas-
filled air
spaces)
Red blood
cell in
capillary
Surfactant-
secreting cell
Squamous
epithelial cell
of alveolar wall

4. Events of Respiration Pulmonary ventilation External respiration
air into and out of the lungs (breathing)
External respiration
gas exchange between pulmonary blood and alveoli
Oxygen into blood; Carbon dioxide out of blood
Respiratory gas transport
O2 and CO2 transported in the bloodstream
Internal respiration
gas exchange between blood tissue cells
© 2015 Pearson Education, Inc.

5. Pulmonary Ventilation inspiration
air flows into lungs
Diaphragm and external intercostal muscles contract
The size of the thoracic cavity increases
External air is pulled into the lungs as a result of:
Increase in intrapulmonary volume
Decrease in gas pressure
© 2015 Pearson Education, Inc.

6. Figure 13.7a Rib cage and diaphragm positions during breathing.
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral
dimensions
Ribs elevated
as external
intercostals
contract
External
intercostal
muscles
Full inspiration
(External
intercostals contract)
Diaphragm moves
inferiorly during
contraction
(a)
Inspiration: Air (gases) flows into the lungs

7. to atmospheric pressure
Figure 13.8 Changes in intrapulmonary pressure and air flow during inspiration and expiration.
Inspiration
Expiration +2
Intrapulmonary
pressure +1
to atmospheric pressure
Pressure relative −1 −2
(a)
Volume of
breath
0.5
Volume (L)
−0.5
(b)

8. Pulmonary Ventilation expiration
air flows out of lungs
Muscles relax
Decrease in intrapulmonary volume
Increase in gas pressure
passive process; affected by lung elasticity
Forced expiration occurs mostly by contraction of internal intercostal muscles to depress the rib cage
© 2015 Pearson Education, Inc.

9. Figure 13.7b Rib cage and diaphragm positions during breathing.
Changes in anterior-posterior and
superior-inferior dimensions
Changes in lateral
dimensions
Ribs depressed
as external
intercostals relax
External
intercostal
muscles
Expiration
(External
intercostals relax)
Diaphragm moves
superiorly as
it relaxes
(b)
Expiration: Air (gases) flows out of the lungs

10. to atmospheric pressure
Figure 13.8 Changes in intrapulmonary pressure and air flow during inspiration and expiration.
Inspiration
Expiration +2
Intrapulmonary
pressure +1
to atmospheric pressure
Pressure relative −1 −2
(a)
Volume of
breath
0.5
Volume (L)
−0.5
(b)

11. Significance of intrapleural pressure
intrapleural pressure - pressure within the pleural space is always negative
keeps lungs from collapsing
Atelectasis is collapsed lung due to:
Pneumothorax- the presence of air in the intrapleural space due to disruption of the fluid bond between the pleural layers
Can be caused by impact/injury/infection
© 2015 Pearson Education, Inc.