1. The exchange of gases between an organism and its environment
Respiration
The exchange of gases between an organism and its environment

2. 2 types: Organismic Aerobic cellular respiration
Oxygen taken up from environment and delivered to individual cells
Simple diffusion
Respiratory systems
Aerobic cellular respiration
Cells use O2 as final electron acceptor to produce energy
CO2 created as waste

3. Gas Exchange Requires MOIST MEMBRANES Air Water
Higher concentration of O2
Less viscous than water
O2 diffuses quickly
Water
Less threat of dessication
More energy needed

4. Respiratory Surfaces Body Surface Tracheal Tubes Gills Lungs
High SA : Volume
Low metabolic rate
Tracheal Tubes
Air enters through spiracles
Branching tubules
Fluid-filled tracheoles = gas exchange
Gills
Folded or split into filaments
Capillaries deliver blood to filaments
Countercurrent exchange
Lungs
Terrestrial
Ingrowth of body cavity

6. Mammalian Respiratory System
Nostrils/Nasal Cavity
Filter
Moisture
Warmth
Pharynx/Larynx
Cartilage give support
Epiglottis closes off larynx during swallowing to prevent choking

7. Trachea Divides into 2 bronchi – lead to each lung
Further divides into bronchioles
Ends at alveoli
Surfactants

8. Ventilation: The Mechanics of Breathing
Inhalation/Inspiration
Thoracic cavity is closed
Diaphragm contracts & moves downward
Ribs may also move upward
Air pressure in lungs falls
Air from outside moves to area of lower pressure

9. Ventilation, cont. Exhalation/Expiration
Diaphragm relaxes
Pressure in cavity increases
Air sacs deflate
Total air in and out during normal/resting breath = tidal volume
Maximum amount exhaled after maximum filling = vital capacity

10. Gas Exchange at Alveoli
Made possible by thin epithelium
Alveoli
Capillaries
Dalton’s Law of Partial Pressure
PO2 = 160 mm Hg
PCO2 = 0.3 mm Hg
Flick’s law of diffusion

11. Gas exchange at tissues
PO2 in arteries ~ 100 mm Hg
PO2 in tissues = 0 – 40 mm Hg
PO2 in veins ~ 40 mm Hg

12. Respiratory Pigments Combine reversibly with O2 Examples:
Hemocyanin
Hemoglobin
Myoglobin
Increases amount of O2 blood can carry from 0.25 mL/100mL to 20 ml/100 mL
% O2 saturation
Affected by pH, temperature, CO2 concentration

13. CO2 Transport Transported in blood in 3 forms:
Dissolved in plasma (10%)
Hb in RBCs (30%)
Causes release of O2
HCO3-
Combination of CO2 & H2O forms carbonic acid
In cells, catalyzed by carbonic anhydrase
Dissociates into H+ & HCO3-
Hb buffers H+
HCO3- diffuses out of cell into plasma
At lung, reaction reverses

14. Regulation of Breathing
Medulla regulates basic rhythm
Pons – controls inhalation/exhalation transition
Chemoreceptors in medulla/aorta/carotid arteries detect changes in CO2 concentration
Increased CO2 lowers blood pH
Respiratory rate increases to get rid of excess CO2