The Respiratory System
Review the anatomy of the respiratory system
Functions of the respiratory system
gas exchange
regulation of acid-base balance
communication
Chemistry and physics of respiration
Boyle’s law 1
P 1V 1 = P 2V 2
mechanism of inhalation
role of diaphragm
role of intercostal muscles
mechanism of expiration
role of diaphragm
role of intercostal muscles
respiratory volumes
measurable volumes
tidal volume
anatomic dead space
inspiratory reserve volume
expiratory reserve volume
residual volume
calculated capacities
inspiratory capacity
functional residual capacity
vital capacity
total lung capacity
Charles’ law
V1/T1 = V2/T2
molecular basis of gas diffusion
net diffusion of a gas in one direction depends on concentration gradient
gas pressures in a mixture of gases depends on partial pressures
Dalton’s law of partial pressures
Ptotal = P1 + P2 + P3 + ... + Pn
Henry’s law 2
concentration of dissolved gas = pressure × SC
Gas Solubility coefficient
O2
0.024
CO2
0.57
N2
0.012
vapor pressure of water: 47 mm Hg at 37 °C
pressure gradient for diffusion 3
D (∆P × A × S)/(d × (MW)0.5)
where D = diffusion rate; A = cross-sectional area; S = solubility
diffusion coefficient = S/(MW)0.5
Gas Relative diffusion coefficient
O2
1.0
20.3
CO2
N2
0.53
Composition of atmospheric, humidified, alveolar, and expired
air
Gas
Atmospheric air
Humidified air
Alveolar air
Expired air
partial
partial
partial
partial
percent
percent
percent
percent
pressure
pressure
pressure
pressure
N2
597.0
78.5
563.4
74.1
569.0
74.9
566.0
74.5
O2
159.0
20.9
149.3
19.6
104.0
13.7
120.0
15.8
CO2
0.3
0.04
0.3
0.04
40.0
5.26
27.0
3.55
H 2O
3.7
0.49
47.0
6.18
47.0
6.18
47.0
6.18
Diffusion of gases through the respiratory membrane
factors affecting
thickness of membrane [0.63 µm on average]
surface area of membrane
diffusion coefficient
pressure difference
Types of respiration
internal respiration
external respiration
Transport of oxygen and carbon dioxide
role of hemoglobin in oxygen transport
Hb + 4(O2) ↔ Hb(O2)4
heme
oxygen-hemoglobin dissociation curve
partial pressure of oxygen
pH
temperature
BPG (or DPG)
fetal hemoglobin
hypoxia - inadequate oxygenation
anemic hypoxia
stagnant hypoxia
hypoxic hypoxia
histotoxic hypoxia
carbon dioxide transport
in solution
as carbaminoHb
Hb + CO2 ↔ HbCO2
as bicarbonate ion
H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3-
Control of respiration
brainstem centers
medullary respiratory centers
dorsal respiratory group
pacemaker functioning for inspiration
ventral respiratory group
mixed functioning for inspiration and expiration
pontine respiratory group
pneumotaxic area inhibits DRG
apneustic center
prevents inhibition of DRG
chemoreceptors and chemosensitive area
hydrogen ions
aortic bodies
carotid bodies
Go to beginning
Questions for thought
1.
2.
3.
4.
5.
Explain the significance of (a) Boyle’s law, (b) Dalton’s law, and (c) Henry’s
law to the process of respiration.
What are the differences between pulmonary volumes and respiratory
capacities? Make sure you list each, and describe how each is determined.
What is the functional difference between the dorsal respiratory group
(DRG) and the ventral respiratory group (VRG) of the brainstem?
Ms Vandross is admitted to the ER after having been rescued from her
closed garage where she was working on her auto, but had left the engine
running. The physician in charge places her on 100% O2. Shortly thereafter,
she stops breathing and dies. What was the error? And what should have
been done?
Discuss the effects of hyperventilation on blood oxygen, carbon dioxide,
and pH.
6. Describe how oxygen and carbon dioxide are transported in the blood.
Go to beginning
Links
{
Referenced sites
z 1 A Java applet illustrating Boyle’s law in action
z 2
Full discussion of Henry’s law
z 3
{
A technical sidebar with some biological problems concerning diffusion
Other sites
z ChemTutor’s overview of gases and the gas laws
[ Anatomy & Physiology 3 syllabus ]
[ Page created 29 April 1999 ][ Last update 05 April 2007 ]
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