1. Respiratory System
ROLE: To bring oxygen into the body and to get rid of the carbon dioxide from the body.

2. The respiratory system

3. The respiratory system

4. Mechanisms of breathing – inspiration
When you breathe in:
Intercostal muscles pull ribs up and out
intercostal muscles between the ribs contract, pulling the chest walls up and out
the diaphragm muscle below the lungs contracts and flattens, increasing the size of the chest
the lungs increase in size, so the pressure inside them falls. This causes air to rush in through the nose or mouth.
Diaphragm contracts and moves down

5. Mechanisms of breathing – expiration
When you breathe out:
Ribs move in and down
Intercostal muscles between the ribs relax so that the chest walls move in and down.
The diaphragm muscle below the lungs relaxes and bulges up, reducing the size of the chest.
The lungs decrease in size, so the pressure inside increases and air is pushed up the trachea and out through the nose or mouth.
Diaphragm relaxes and bulges up

6. Mechanisms of breathing – inspiration

7. Mechanisms of breathing – expiration

8. The respiratory system

9. Respiratory system – 3 main processes
Pulmonary respiration
The breathing of air into and out of the lungs
External respiration
Exchange of O2 and CO2 between the lungs and the blood
Internal respiration
Exchange of O2 and CO2 between the blood and muscle tissues

10. Gaseous Exchange
Gaseous exchange refers to the exchange of gases, namely O2 and CO2 and relies on a process called diffusion

11. How does Diffusion happen?
PP – partial pressure of a gas is the pressure it exerts within a mixture of gases.
EXAMPLE:
Air – Nitrogen (79%); Oxygen (21%); Carbon Dioxide (0.03%)
Together they exert a pressure of 760mmHg but individually they exert pressures of:
O2 – 160mmHg
How do you work it out? –
Partial Pressure = Atmospheric pressure x fractional concentration
760mmHg x 0.21 = 159.6mmHg
* Gases always move from an area of high pressure to an area of low pressure

12. Diffusion
Diffusion is the movement of gases from an area of high pressure to an area of low pressure.
The difference between the high and low pressure is called the diffusion gradient – the bigger the gradient, the greater the diffusion and gaseous exchange that takes place.

13. Gas exchange at the alveoli

14. External Respiration (Alveoli) – What makes it so efficient?
Alveoli walls very thin – diffusion distance is very short.
Huge amount of alveoli with massive surface area for diffusion
Vast supply of capillaries – huge surface area for diffusion
Diameter of capillaries is slightly narrower than area of red blood cells
Causes red blood cells to distort to increase surface area for gas exchange
Forces red blood cells to go through capillaries in single file to maximise exposure to oxygen

15. Internal Respiration (muscles) – why is it so efficient?
Big diffusion gradient (65mmHg)
Myoglobin in muscles has a higher affinity for oxygen than haemoglobin sp attracts oxygen from blood
Extensive capillary network – huge surafce area
Capillary wall only one cell thick – very short distance for diffusion