1. 6.4 Gas Exchange
Respiratory System

2. Why do we need to breathe?
To intake oxygen
To exhale carbon dioxide
What is oxygen used for?
Aerobic respiration
And what is aerobic respiration used for?
Energy production (ATP!)

3. Definitions: Ventilation, Gas Exchange, and Cell Respiration
The process of inhaling and exhaling, with oxygen entering the alveoli (large surface area)
Gas Exchange
The process of exchanging one gas for the other between alveoli and capillaries (carbon dioxide for oxygen)
Cell Respiration
The chemical process occurring in mitochondria where energy is released as ATP

4. What composes the human respiratory system?
Mouth
Nose
Trachea
Bronchi
Bronchioles
Lungs
Alveoli

5. Identify the respiratory components.6 1 7 3 2 3 4 5

6. Be able to draw something like this.

7. Why are alveoli shaped like they are?
Small alveoli increase surface area of tissue exposed to open air
Gases only have to go through one layer of cells (thin capillary wall) to get into blood vessel
There are so many capillaries blood easily diffuses

8. How is air drawn into the lungs?
Diaphragm muscle contracts
Intercostal muscles between ribs contract
Lungs can open up more
More volume with same amount of gas = decreased air pressure
Air rushes into lungs to balance pressure

9. How is air pushed out of the lungs?
Diaphragm muscle relaxes
Pushes on lungs to “deflate”
Intercostal muscles relax
Chest cavity gets smaller
Pushes air out of lungs
Air is exhaled

10. IB Exam Question
1. State the difference between ventilation, gas exchange, and cell respiration. (3 marks)
Ventilation
The process of inhaling and exhaling, with oxygen entering the alveoli (large surface area)
Gas Exchange
The process of exchanging one gas for the other between alveoli and capillaries (carbon dioxide for oxygen)
Cell Respiration
The chemical process occurring in mitochondria where energy is released as ATP

11. 2. Draw a diagram of the human gas exchange system. (5 marks)
IB Exam Question
2. Draw a diagram of the human gas exchange system (5 marks)
Award [1] for each of the following structures clearly drawn and labelled.
mouth / nose;
trachea;
bronchi;
bronchioles;
lungs;
alveoli;
diaphragm;
ribs / rib eye / intercostal muscles;

12. IB Exam Question
3. List the features of the alveoli that adapt them to gas exchange (3 marks)
Alveoli increase surface area between blood and respiratory gases
Single layer of cells allows for short diffusion distance of gas into blood
Dense network of capillaries near the surface increases absorption

13. IB Exam Question
4. Explain the need for, and the mechanism of, ventilation of the lungs in humans (8 marks)
draws fresh air / oxygen into the lungs;
removal / excretion of CO2;
maintains concentration gradient of O2 / CO2 / respiratory gases;
diaphragm contracts;
intercostal muscles contract;
increased volume (of thorax / thoracic cavity);
decreasing air pressure in lungs;
air rushes in down air pressure gradient;
opposite of the above causes exhalation;
abdominal muscles contract during active exhalation;
elastic recoil of lungs helps exhalation;