1. Gas Exchange (Core)

2. Assessment Statements Obj. 6.4.1 2 6.4.2 3 6.4.3 6.4.4 1 6.4.5
Distinguish between ventilation, respiration and gas exchange. 2
6.4.2
Explain the need for a ventilation system. 3
6.4.3
Describe the features of alveoli that adapt them to gas exchange.
6.4.4
Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli. 1
6.4.5
Explain the mechanism of ventilation of the lungs, in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles.
Command terms:
Assessment statements from: Online IB Biology Subject Guide

5. Why do we need a ventilation system?
We are large organisms. Oxygen cannot diffuse into all our
cells directly from the air, nor can waste products be directly
ejected from the body. We have specialised organ systems,
which are efficient, but need delivery of nutrients and
removal of waste. The ventilation system ensures the blood
can be the medium for this.
We are land-borne. Gases need moist surfaces (membranes) in
order to diffuse. Our lungs are moist membranes, allowing
oxygen to diffuse into the blood and carbon dioxide
to diffuse out.
The ventilation system maintains a large
concentration gradient between the alveoli and
the blood. The constant flow of past the alveoli brings
blood with a high CO2 concentration and low O2
concentration. Breathing out keeps the CO2 concentration
in the alveoli low, so it diffuses out of the blood.
Breathing in keeps O2 concentration in the alveoli high,
so it diffuses into the blood.
Diagram from:

6. http://highered. mcgraw-hill

9. Type I & II Pneumocytes Type I Adapted to carry out gas exchange
Large total surface area for diffusion
Make up majority of epithelial cells lining the alveoli
Flattened cells
Adjacent cells also single cell layer thick
Type II
Secrete a solution containing a surfactant creating a moist surface preventing cell adherence
Moisture allows oxygen to dissolve and diffuse into blood in cappillaries and for CO2 to evaporated into air and be exhaled
Rounded cells

10. Which process(es) of membrane transport are being used in gas exchange at the membranes of the alveoli?

13. Airways Airways: nose, mouth  trachea.
Trachea has rings of cartilage keeping open.
Trachea divides into 2 bronchi, also strengthened with cartilage.
In lungs bronchi dived to form narrower and narrower bronchioles w/ smooth muscle fibers in their walls.
Alveoli at very end of bronchioles

14. Pressure changes
Muscles contraction cause pressure changes forcing air in and out of lungs
Muscle contractions cause pressure inside thorax to drop below atmospheric pressure
Air is drawn into lungs from atmosphere until pressure in lungs equals atmospheric pressure
Muscle contractions cause pressure in thorax to rise inside thorax above atmospheric pressure, so air is forced out from lungs to atmosphere.

15. Antagonistic muscles
Muscles shorten when contracting and lengthen when relaxing
Only cause movement in one direction
Inspiration and expiration involve opposite movements so different muscles are required working in antagonistic pairs

16. See chart on page 315-316 in text book.

18. Emphysema

19. Lung cancer

20. @IBiologyStephen
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