1. Structure of the Respiratory System

2. Overall Function of the Lungs
The lungs function in the human body to exchange the Carbon Dioxide (CO2) produced in our tissues as they complete cellular processes for fresh Oxygen (O2) that our body needs to carry out those cellular processes.

3. Gas Exchange in the Lungs

4. Mechanism of Inspiration

5. Mechanism of Expiration

6. Factors that Control Oxygen Diffusion into the Blood
The oxygen pressure gradient between the alveolar air and incoming pulmonary blood
The total functional surface area of the respiratory membrane
The respiratory minute volume (respiratory rate/minute X volume of air/inspiration)
Alveolar ventilation (amount of air that actually reaches the alveoli)

7. Pulmonary gas exchange
Pulmonary gas exchange. A, As blood enters a pulmonary capillary, oxygen diffuses down its pressure gradient (into the blood). Oxygen continues diffusing into the blood until equilibration has occurred (or until the blood leaves the capillary). B, As blood enters a pulmonary capillary, carbon dioxide diffuses down its pressure gradient (out of the blood). As with oxygen, carbon dioxide continues diffusing as long as there is a pressure gradient. Po2 and Pc2 remain relatively constant in a continually ventilated alveolus.

8. Transport of Oxygen in our Blood

9. Transport of CO2 in Our Body

10. Systemic gas exchange. A, As blood enters a systemic capillary, O2 diffuses down its pressure gradient (out of the blood). O2 continues diffusing out of the blood until equilibration has occurred (or until the blood leaves the capillary). B, As blood enters a systemic capillary, CO2 diffuses down its pressure gradient (into the blood). As with O2, CO2 continues diffusing as long as there is a pressure gradient.

11. Regulation of Breathing