Physiotherapy Question:

Answer #1
A man can live without food for a few days, but without air
he cannot live even for five minutes. The moment he is born
he begins to breathe will continue to breath till he is
alive. During the process of breathing he draws some are
into his body and expels some. If this supply if air is cut
off, he is suffocated and dies.

The air we breathe in is taken
into the lungs through the wind pipe. The lunge are situated
in the chest-one in each side of the body. The air we breath
in contains oxygen to the extent of one-fifth of the volume
of air. The oxygen is dissolved in the blood and is carried
to all parts of the body. The oxygen combines with the
tissues and sets free the energy contained in them. The
combination of oxygen with a substance is known as the
process of oxidation, combustion or burning is going on in
the human body every moment of the life of a man-whether he
is awake or asleep. Heat is, of course, generated, but there
is no fire.

The whole system of
respiration can be summarized as follows :
(1) Pure blood received from the lungs is pumped by the
heart into the large arteries.
(2) Veins bring impure blood from various parts of the body
and pour it into the heart.
(3) The heart pumps it out into the lungs for purification.
Thus a cycle is formed and the process is automatic. Lungs
are the most important part of this system, because it is
they that purify the impure blood and discharge waste
products like carbon dioxide. The other parts of the
respiratory system are :
(a) the nose.
(b) The upper part of the wind-pipe which is modified into
the voice box known as larynx.
(c) The wind-pipe.
(d) The lungs.

Answer #2
The respiratory system works with pressure differences between atmosphere and inside the lungs. Inspiration occurs when the respiratory muscle causes the lungs to expand thereby creating a net negative pressure ( P=f/a) and air sucks/draws in. During this period gaseous exchange occur due to concentration differences. Then the muscles relax and the elastic forces of the expanded lungs forces air out due positive pressure built in the lungs v/s atmosphere. The process repeats with fresh air.