Air is filtered. The moist surface of the lining of the nasal
cavity, and the hairs growing from its sides, remove some
of the tiny particles of dirt in the air. In addition, as the
inhaled air passes through the nasal cavity, its temperature
is brought close to that of the body, and it takes up water
vapour so that it becomes more moist than before.
Pharynx:
Warming and moistening goes on in this common passage
of digestive and respiratory system. Epiglottis, a flap like
muscular valve controls movement of food and air towards
their respective passages.
Larynx:
This stiff box contains our vocal cords. When air passes
out of the lungs and over the vocal cords, it causes them
to vibrate. This produces sounds on the basis of our
speech, song etc.
Trachea:
Wind pipe channeling air to lungs. Touch your throat to
feel the tube like structure.
Bronchus:
At its lower end the trachea or the wind pipe divides into
two bronchi-one leading to each lung.
Bronchioles:
Each bronchi is further divided into smaller and smaller
branches called bronchioles.
Alveolus:
These finally terminate in clusters of air sacs called
alveoli in the lungs which are very small and numerous.
Gaseous exchange takes place here as blood capillaries
take up oxygen and expel carbon dioxide.
Blood:
Blood carries oxygen, to each and every cell of the body
and collects CO2 from them.
The whole passage from nostrils to alveolus is moist and warm
