Respiratory Systems
Types of Respiration
• External
• Internal
Is the volume of air that you breath
in equal to the volume of air that
you breath out?
No. Typically, you burn more O2 than you release CO2 so more
oxygen goes into your body than CO2 comes out. This ratio is
typically 8 CO2 out for every 10 O2 in.
Respiratory Quotient
(Carbon dioxide Production / Oxygen Consumption)
• Carbohydrates
1.0
• Proteins
0.8
• Fats
0.7
• AVERAGE
0.8
4 Steps to Movement of Oxygen
• Ventilation
BULK
• Lung Diffusion
DIFFUSION
• Blood Transport
BULK
• Tissue Diffusion
DIFFUSION
Figure 44-1
1. Ventilation
2. Gas
3. Circulation
Environment
Ventilatory surface
exchange
Respiratory system
4. Cellular
respiration
Blood
Mitochondria
Circulatory system
Figure 44-5
Diffusion constant
(depends on
solubility of gas
and temperature)
Area for
gas exchange
Difference in partial
pressure of gas on either
side of barrier to diffusion
Distance
(thickness of
barrier to diffusion)
Partial Pressures
• % Gasses in Air
– 79% “Nitrogen” (78.09% nitrogen; 0.93% argon)
– 20.95% Oxygen
– 0.038% Carbon Dioxide
• Partial Pressure of Gases in air
– Nitrogen .79
* 760 mmHg = 600 mmHg
– Oxygen .2095 * 760 mmHg = 159 mmHg
– CO2
.00038 * 760 mmHg = 0.29 mmHg
Partial Pressures in Air and in
Water
Figure 44-5
Diffusion constant
(depends on
solubility of gas
and temperature)
Area for
gas exchange
Difference in partial
pressure of gas on either
side of barrier to diffusion
Distance
(thickness of
barrier to diffusion)
Movement of O2 and CO2 is
always “downhill”
• Oxygen and Carbon Dioxide dissolve into
the body fluid
• O2 and CO2 are freely permeable to cell
membranes
• They can not be pumped or transported
against a concentration gradient
• They can be taken out of solution or
converted to other chemicals for storage.
• However, movement is always downhill
Mammalian Respiratory System
Breathing Air vs. Breathing Water
Water
Air
O2 Concentration
(liter/liter)
0.007
0.21
1:30
Density (kg/liter)
1
0.02
800:1
Liters of medium
per liter O2
143
4.8
30:1
0.0062
23,000:1
Kilograms medium 143
per liter O2
Ratio:water/air
Variations in O2, CO2, and pH
in a tidal rock pool
Stagnant water can have a very
low oxygen partial pressure
Fish
Respiratory
System
Figure 44-8
Countercurrent flow
Co-current flow
(seen in fish gills)
(not seen in fish gills)
Water flow over lamellae
(% oxygen)
100% 70% 40% 15%
Water flow over lamellae
(% oxygen)
100%
90%
O2
90%
60%
70%
Diffusion
stops
O2
30%
5%
Blood flow through lamellae
(% oxygen)
0%
10%
50%
30%
50%
Blood flow through lamellae
(% oxygen)
Insect Respiratory System
Breathing
through the
anus
Breathing through Skin alone
(large animal)
Figure 44-26
Tissues
PO2 40 mm Hg
PCO2 45 mm Hg
Blood leaving
tissue capillaries
PO2 40 mm Hg
PCO2 45 mm Hg
Blood entering
tissue capillaries
PO2 140 mm Hg
PCO2 40 mm Hg
Systemic
circulation
Inhaled air
PO2 160 mm Hg
PCO2 0.3 mm Hg
Exhaled air
PO2 120 mm Hg
PCO2 27 mm Hg
Pulmonary Pulmonary
Aorta artery
vein
Pulmonary circulation
Venae
cavae
Blood entering
alveolar
capillaries
PO2 40 mm Hg
PCO2 45 mm Hg Alveoli of lungs
PO2 104 mm Hg
PCO2 40 mm Hg
Blood leaving
alveolar
capillaries
PO2 104 mm Hg
PCO2 40 mm Hg
PO2
&
PCO2
Atmospheric CO2 = 397 ppm
(March 2013 Mauna Loa Observatory)
397 ppm = 0.000397 (divide by 1,000,000)
Percent
= 0.0397%
Partial Pres. = 0.3 mmHg
(760mmHg x 0.000397)
Gas Exchange in Lung
PO2
&
PCO2
O2 Transport in Blood
1 Liter of blood contains 200 ml Oxygen
(assuming normal levels of Hemoglobin)
• Dissolved in plasma - 1.5% (3 ml O2)
• Bound to Hemoglobin - 98.5% (197 ml O2)
Oxyhemoglobin Dissociation Curve
200
150
ml O2
L blood
100
50
0
Figure 44-18
Bohr Shift-Decreased binding of O2 to hemoglobin with
Bohr shift
% O2 unloaded
pH 7.2
% O2 unloaded
-increased temperature
-increased CO2
-decreased pH
pH 7.4
Figure 44-19
Fetal
hemoglobin
Adult (maternal)
hemoglobin
CO2 Transport in the Blood
• Dissolved in plasma
10%
• Bound to Hemoglobin
30%
• Converted to bicarbonate
60%
CO2 + H2O <-> H2CO3 <-> HCO3- + H+
CO2 Transport:
1)Dissolved,
2)Bound to Hb
3)Bicarbonate
*Note that CO2
has a big impact
on pH.
Fick Principle of O2 transport
O2 delivery = C.O. * ([O2] a – [O2] v)