Page 379 - Primary Six Notes

Functions of parts of the breathing system

1. The nose and nasal cavity

 It contains mucus which warms and moistens air before

reaching the lungs.

 It contains hair like structures called Cilia that trap germs

and dirt that may otherwise enter the nose.

 Air is filtered (cleaned) warmed and moistened.

2. Mouth or oral cavity

 Mouth is a secondary external opening for the respiratory

tract. Mouth can be used to supplement or replace the nose’s

function when needed.

 The mouth does not warm and moisturise the air entering

the lungs. It also lacks the hairs and sticky mucus that filter

air passing through the nose.

 The one advantage of breathing through the mouth is that its

shorter distance and larger diameter allows air to quickly

enter the body.

4. Larynx

The larynx has three main functions:

i. a passageway for air

ii. a valve to close off the air passage from the digestive one

(the epiglottis)

iii.a voice box.

5. Pharynx or throat

The pharynx is shared with the digestive system. The epiglot-

tis ensures that air passes into the trachea.