1. Concept 42.5: Gas exchange occurs across specialized respiratory surfaces page 915
Gas exchange supplies O2 for cellular respiration and disposes of CO2
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2. Some comparisons we will be making
Bacteria
Protists
Worms
Insects
Fish
Amphibians
Reptiles
Mammals

3. Partial Pressure Gradients in Gas Exchange
A gas diffuses from a region of higher partial pressure to a region of lower partial pressure
Partial pressure is the pressure exerted by a particular gas in a mixture of gases
Gases diffuse down pressure gradients in the lungs and other organs as a result of differences in partial pressure
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4. Partial Pressure Gradients in Gas Exchange
A gas diffuses from a region of higher partial pressure to a region of lower partial pressure
Partial pressure is the pressure exerted by a particular gas in a mixture of gases
Gases diffuse down pressure gradients in the lungs and other organs as a result of differences in partial pressure
What gas is most prevalent in air?
What percent of air is oxygen?
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5. Composition of Air Air contains:
Air at sea level is at a pressure of 760 mmHg. What is the partial pressure of O2 at sea level?
760 mmHg X 20.95=159.2 mmHg

6. How can organisms take in needed oxygen and expel CO2?

7. Respiratory Surfaces
Animals require large, moist respiratory surfaces for exchange of gases between their cells and the respiratory medium, either air or water
Gas exchange across respiratory surfaces takes place by diffusion
Respiratory surfaces vary by animal and can include the outer surface, skin, gills, tracheae, and lungs
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8. 6 mechanisms for gas exchange
1. Diffusion through cell membrane
Ex: Single Cell
2. Diffusion through skin
Ex: Earthworm
3. Papillae- Increased folds in skin
Ex: Echinoderms
4. Spiracles and tracheae
Ex: Insects
5. Gills
Ex: Fish
6. Alveoli of Lungs
Ex: Mammals

9. Gills in Aquatic Animals
Gills are outfoldings of the body that create a large surface area for gas exchange
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10. Figure 42.22 Gills are Shown In Pink
Coelom
Gills
Gills
Figure Diversity in the structure of gills, external body surfaces that function in gas exchange.
Tube foot
Parapodium
(functions as gill)
(a) Marine worm
(b) Crayfish
(c) Sea star

11. Ventilation moves the respiratory medium over the respiratory surface
Aquatic animals move through water or move water over their gills for ventilation
Fish gills use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills; blood is always less saturated with O2 than the water it meets
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12. Countercurrent exchange PO (mm Hg) in water 2
Figure 42.23
O2-poor blood
Gill
arch
O2-rich blood
Lamella
Blood
vessels
Gill arch
Water
flow
Operculum
Water flow
Blood flow
Countercurrent exchange
Figure The structure and function of fish gills.
PO (mm Hg) in water 2
150
120 90 60 30
Gill filaments
Net diffu-
sion of O2
140
110 80 50 20
PO (mm Hg)
in blood 2

13. Tracheal Systems in Insects
The tracheal system of insects consists of tiny branching tubes that penetrate the body
The tracheal tubes supply O2 directly to body cells
The respiratory and circulatory systems are separate
Larger insects must ventilate their tracheal system to meet O2 demands
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14. Tracheoles Mitochondria Muscle fiber 2.5 m Body cell Tracheae Air sac
Figure 42.24
Tracheoles
Mitochondria
Muscle fiber
2.5 m
Body
cell
Tracheae
Air
sac
Tracheole
Figure Tracheal systems.
Air sacs
Trachea
Air
External opening

15. Amphibians and Reptiles
Amphibians have lungs but also supplement their respiration through moist skin- cutaneous respiration.
Reptiles have a partially divided ventricle that more efficiently separates oxygenated from deoxygenated blood, reducing the need for cutaneous respiration. Turtles supplement their respiration through skin on their ____!

16. What structures are involved in mammal gas exchange?

17. Mammalian Respiratory Systems: A Closer Look
A system of branching ducts conveys air to the lungs
Air inhaled through the nostrils is warmed, humidified, and sampled for odors
The pharynx directs air to the lungs and food to the stomach
Swallowing tips the epiglottis over the glottis in the pharynx to prevent food from entering the trachea
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18. enveloping alveoli (SEM)
Figure 42.25
Branch of
pulmonary vein
(oxygen-rich
blood)
Branch of
pulmonary artery
(oxygen-poor
blood)
Terminal
bronchiole
Nasal
cavity
Pharynx
Left
lung
Larynx
(Esophagus)
Alveoli
Trachea
50 m
Right lung
Capillaries
Bronchus
Figure The mammalian respiratory system.
Bronchiole
Diaphragm
(Heart)
Dense capillary bed
enveloping alveoli (SEM)

19. Exhaled air passes over the vocal cords in the larynx to create sounds
Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs
Exhaled air passes over the vocal cords in the larynx to create sounds
Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx
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20. Gas exchange takes place in alveoli, air sacs at the tips of bronchioles
Oxygen diffuses through the moist film of the epithelium and into capillaries
Carbon dioxide diffuses from the capillaries across the epithelium and into the air space
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21. Let’s model how the blood gets oxygen to every body cell.
Oxygen in the blood is affixed to _______
The more that the tissue needs oxygen, the lower the affinity of hemoglobin for oxygen.

22. Modeling O2 Delivery 8 students are hemoglobin- cups with 4 O
Each table is a body cell- 1 cup with 4 O
Body cells are digestive, brain, skeletal muscle
Every hemoglobin has a route, one row.
Body Cells use O2
Warm up- Every cell uses 1/ 20 sec
Raise hand when need an oxygen
Active tissue uses 1/10 sec, vary which tissue is active

23. Figure 42.31 Oxyhemoglobin dissociation curve
100
100
O2 unloaded
to tissues
at rest
pH 7.4 80 80
pH 7.2
O2 unloaded
to tissues
during exercise
Hemoglobin
retains less
O2 at lower pH
(higher CO2
concentration) 60 60
O2 saturation of hemoglobin (%)
O2 saturation of hemoglobin (%) 40 40 20 20 20 40 60 80
100 20 40 60 80
100
Figure Dissociation curves for hemoglobin at 37°C.
PO (mm Hg)
Tissues during
exercise
Tissues
at rest
Lungs 2
(b) pH and hemoglobin dissociation
PO (mm Hg) 2 2
(a) PO and hemoglobin dissociation at pH 7.4

24. O2 saturation of hemoglobin (%)
Figure 42.31b
100
pH 7.4 80
pH 7.2
Hemoglobin
retains less
O2 at lower pH
(higher CO2
concentration) 60
O2 saturation of hemoglobin (%) 40 20
Figure Dissociation curves for hemoglobin at 37°C. 20 40 60 80
100
PO (mm Hg) 2
(b) pH and hemoglobin dissociation

25. Oxyhemoglobin dissociation curve
What effect does exercise have on the curve?
How do you think a fetus’ curve would look
(shift left or shift right?).