3. The beginning. Oxygen first enters your body and Carbon Dioxide leaves Air enters the nose and is filtered by tiny hairs called cilia, it is moistened by the mucus that lines the nasal passage. The cilia and the mucus filter dust and pathogens from the air.

4. Air can also get into your body through your mouth or the oral cavity but air is not filtered as much when it enters in through your mouth

5. Pharynx or throat This is where the air passes from your nose to your bronchi tubes and lungs Your pharynx (throat) gathers air after it passes through your nose and then the air is passed down to your trachea (windpipe).

6. Long structure made up of soft tissue that connects the mouth and nose to the lungs The trachea is held open by partial (or incomplete) rings of cartilage Without these rings your trachea might close off and air would not be able to get to and from your lungs.

7. Your trachea splits up into two bronchi tubes. Each branch going to a lung The bronchi tubes are like tree branches that get smaller and smaller, till they become the bronchiole At the end of the bronchiole are tiny air sacs called Alveoli

8. There are 300 – 600 million alveoli in the lungs. They are tiny air sacs that are highly folded and fill up with air/oxygen when you breathe in Your alveoli are surrounded by many tiny blood vessels called capillaries

9. Respiratory system is the system that helps you breathe in and out Oxygen (O 2 ) can be pumped through your body Carbon dioxide (CO 2 ) can be removed from the blood stream.

10. An internal structure to avoid water loss by evaporation Flow of air: Nose /mouth – Larynx – Trachea – Bronchi – Bronchiole – Alveoli – Closed Blood Vessels System of tubes is restricted to one body area (the Thoracic Cavity) Gas exchange surface is the wall of the alveolar sac because it is wet, thin and highly folded.

11. Requirements of a successful respiratory surface: Large surface area Very thin (one-cell thick) Moist or wet surface

12. The walls of your alveoli (and capillaries) are so thin that the oxygen or carbon dioxide can pass through them, traveling right into, or out of your blood stream

13. Diffusion of O 2 and CO 2 is driven by pressure gradient (gases move from areas of higher partial pressure to lower partial pressure.) Direction of O 2 : lungs to cells Direction of CO 2 : cells to lungs Primary Transport forms Oxygen: as O 2 bound to hemoglobin Carbon Dioxide: As HCO 3 - (bicarbonate in plasma)

14. CO 2 is produced at the tissue level Red Blood Cells convert CO 2 to HCO 3 - HCO 3 - dissolved travels to lungs Tissue-Level reactions are reversed within the lung CO 2 is produced, then exhaled

15. INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up)

16. Rest Ventilation rate 12 breaths per minute Tidal Volume 0.5 L Total Ventilation 6.0 L per minute of air Exercise Ventilation rate 48 breaths per minute Tidal Volume 4.0 L Total Ventilation 192 L per minute of air