1. Gas exchange

2. Key concepts
Gas exchange occurs across specialized respiratory surfaces
Gills in aquatic animals
Tracheal systems in insects
Lungs
Breathing ventilates the lungs
Amphibian breathing
Bird breathing
Control of breathing in humans
Respiratory pigments bind and transport gases
Diffusion and partial pressure
Respiratory pigments
O2 and CO2 transport

3. Vocabulary words ventilation lungs vocal cords bronchioles diaphragm
respiratory surface
tracheal system
larynx
bronchi (bronchus)
breathing
vital capacity
partial pressure
dissociation curve for hemoglobin
ventilation
lungs
vocal cords
bronchioles
diaphragm
residual volume
respiratory pigments
Bohr shift
countercurrent exchange
gills
trachea
alveoli (alveolus)
tidal volume
breathing control centers
hemoglobin
carbon dioxide transport

4. Respiratory surfaces and gas exchange
Gas exchange – uptake of O2 from environment and discharge of CO2
Mitochondria need O2 to produce more ATP, CO2 is the by-product
C6H12O6 + 6O2  6CO2 + 6H2O + 36 ATP
Diffusion rate
α SA  large
α 1/d2  thin
Moist so gases are dissolved first
DIFFUSION

5. Respiratory surfaces and gas exchange
Size of organism
Habitat
Metabolic demands
Unicellular organisms
Entire surface area for diffusion
Simple invertebrates
Sponges, cnidarians, flatworms
diffusion

6. Respiratory surfaces and gas exchange
More complex animals
Thin, moist epithelium
Separates medium from capillaries
Entire outer skin  small, long, thin organisms
Specialized respiratory organs that are extensively folded and branched

7. Gills in aquatic animals
Outfoldings of the body surface suspended in water
Sea stars
Segmented worms or polychaetes
Molluscs and crustaceans
Fishes
Young amphibians
Total surface area is greater than the rest of the body

8. Water as a respiratory medium
Just keep swimming swimming swimming!
Surfaces are kept moist
O2 concentrations in water are low
Ventilation – increasing flow of respiratory medium over the surface
Countercurrent exchange – process in which two fluids flow in opposite directions, maximizing transfer rates
Why are gills impractical for land animals?

9. Air as a respiratory medium
Air has a higher concentration of O2
O2 and CO2 diffuse much faster in the air  less ventilation
Difficulty of keeping surface moist
Solution: respiratory infolding inside the body
Tracheal system of insects – network of tubes that bring O2 to every cell
Spiracles

10. Lungs
Heavy vascularized invaginations of the body surface restricted to one location
Found in spiders, terrestrial snails, vertebrates
Amphibians supplement lung breathing with skin
Turtles supplement lung breathing with moist surfaces in mouth and anus

11. Mammalian respiration

12. Lung ventilation through breathing
Positive pressure breathing in frogs
“Gulping in” air
Negative pressure breathing in reptiles and mammals
Rib muscles and diaphragm change lung volume and pressure

13. Lung volumes Factors Tidal volume Vital capacity Sex Height
Volume of air inhaled and exhaled with each breath
Vital capacity
Maximum volume inhaled and exhaled during forced breathing
Residual volume
Air left in alveoli after forced exhalation
Factors
Sex
Height
Smoking
Physical activity
Altitude

14. Avian breathing
Air sacs act as bellows to keep air flowing through the lungs.

15. Control centers in the brain regulate breathing

16. Gases diffuse down pressure gradients concentration and pressure drives the movement of gases into and out of blood

17. Respiratory pigments O2 transport Low solubility of O2 in H2O
Respiratory pigments are proteins with metal atoms
Hemoglobin – Fe
Hemocyanin – Cu
Allow reversible binding of O2
Drop in pH results in a lowered affinity of hemoglobin for O2

18. Respiratory pigments CO2 transport 7% in plasma
23% bound to hemoglobin
70% as HCO3-
buffer
Respiratory pigments

19. Fetal hemoglobin HbF has greater affinity to O2 than Hb
low O2% by time blood reaches placenta
fetal Hb must be able to bind O2 with greater attraction than maternal Hb

20. Deep-diving mammals
Seals, whales, dolphins are capable of long underwater dives
Weddell seal  5% O2 in lungs, 70% in blood
Huge spleen stores huge volumes of blood
Large concentrations of myoglobin in muscles
Heart rate and O2 consumption rate decrease
Blood is redirected from muscles to brain spinal cord and eyes