Chapter 16

Ventilation includes:
 Inspiration (inhalation)
 Expiration (exhalation)



Pressure in lung decreases
Air flows from atmosphere, where pressure is
higher, and into lungs
Why does pressure decrease in lungs during
this time?


Due to elasticity of lungs
Forced expiration helped by thoracic and
abdominal wall muscles
Atmospheric pressure
(760 mm Hg)
Intra-alveolar
pressure
(760 mm Hg)
Intra-alveolar
pressure
(758 mm Hg)
Diaphragm
(a)
(b)


One inspiration
One exhalation

Spirometry: measuring different air volumes

Tidal Volume: amount of air that
enters/leaves lungs during one respiratory
cycle

Normal = 500 mL

Extra volume of air can enter lungs
(Inspiratory Reserve Volume)
 Maximum = 3000 mL

Inspiratory Capacity = IRV + TV

Lungs can expel extra air volume (Expiratory
Reserve Volume)
 1100 mL of air beyond TV

Air leftover = Residual Volume
 1200 mL

Functional Residual Capacity = ERV + RV

IRV + TV + ERV = VC

Maximum volume of air a person can exhale,
after taking the deepest breath possible

VC + Residual Volume = TLC

Varies with age, gender, body size
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Lung volume in milliliters (mL)
6,000
5,000
Inspiratory
reserve volume
Vital
capacity
4,000
3,000
2,000
1,000
Tidal
volume
Residual
volume
Expiratory
reserve volume
Inspiratory
capacity
Total lung
capacity
Functional
residual
capacity
0
*During inspiration, which way would the pen move in this figure?
-Helps evaluate courses of emphysema, pneumonia, lung
cancer (conditions where functional lung tissue is lost)
-Also helps track progress of diseases like bronchial asthma
(obstructs air passages)

Medulla Oblongata!

Movement of particles across a membrane
from areas of high concentration to low
concentration

Gases move from areas of high pressure to
low pressure

Total pressure of air includes the partial
pressure of each gas in the air

Partial pressure of oxygen is higher in alveoli
air than in capillary blood
 Which way will oxygen diffuse?

Partial pressure of carbon dioxide is higher in
capillary blood than in alveoli air
 Which way will carbon dioxide diffuse?
Alveolus
Diffusion of O2
Alveolar
wall
PCO2 = 40 mm Hg
PCO2 = 45 mm Hg
PO2 = 104 mm Hg
PO2 = 40 mm Hg
Diffusion of O2
Blood flow
(to body
tissues)
Blood flow
(from body
tissues)
Capillary
PCO2 = 40 mm Hg
PO2 = 104 mm Hg