RESPIRATION (FORM 3)

THE HUMAN BREATHING MECHANISME

The human respiratory system

1. The human respiratory system supplies oxygen to the body and eliminates carbon dioxide.

figure 1.0 : the human respiratory system.

figure 1.1 :  the structure of human lung

2. The flow of air from the nose to the alveolus in the lungs.

3. Breathing mechanism refers to the physical changes that occur in the human respiratory system during breathing

4. Process of inhalation :

(a) External intercostal muscles contract.

(b) The ribs swing upwards and outwards.

(c) The diaphragm contracts and flattens.

(d) The volume of the thoracic cavity increases

(e) The air pressure in the thoracic cavity decreases.

(f) The atmospheric pressure outside the body is higher than the air pressure in the thoracic cavity.

(g) Air is sucked into the lungs.

5. Process of exhalation :

(a) External intercostal muscles relax.

(b) The ribs swing downwards and inwards

(c) The diaphragm relaxes and curves upwards

(d) The volume of the thoracic cavity decreases.

(e) The air pressure in the thoracic cavity increases.

(f) The atmospheric pressure outside the body is lower than the air pressure in the thoracic cavity.

(g) Air is forced out of the lungs.

5. Model of the human respiratory system can be used to show the action of the diaphragm during breathing.

                                                                                                                                                                   

TRANSPORT OF OXYGEN IN THE HUMAN BODY

Diffusion of oxygen from the alveoli into the blood capillaries