1. Control & Coordination Part 1 The Respiratory System
Year 9 Science 2013
Control & Coordination
Part 1 The Respiratory System

2. Gas Exchange
Oxygen and carbon dioxide need to be exchanged with the environment

3. Diffusion
The process of gas exchange is always by diffusion between the external and internal environment of the organism.

4. Surface Area: Volume
For single-celled and small organisms this is not a problem because of their high surface area to volume ratio.

5. Multicellular Organisms
Large organisms rely on specialised respiratory surfaces.

6. Features of Respiratory Surfaces
Large surface area
Thin, moist and easily penetrable surface.
Adequate ventilation.
Efficient transport of carrier fluid (blood) across respiratory surface.

7. Alveoli The site of gaseous exchange
Increases the surface area for gas exchange.

8. Breathing
Contraction & relaxation of the diaphragm muscle results in changes in pressure within the lung cavity, forcing air in & out.

9. Epiglottis
The epiglottis prevents food from travelling down the trachea and blocking the passage of air.

10. Gas exchange relies on diffusion, therefore concentration gradients need to be maintained.

11. For oxygen to continually diffuse into capillaries around alveoli, oxygen needs to be transported away from the site

12. Respiratory pigments such as haemoglobin carry oxygen in the blood from lungs and release oxygen into cells.

13. Rhythmic pumping of the heart ensures continuous flow of blood along capillaries surrounding the alveoli.

14. Haemoglobin and oxygen bind in a reversible reaction.