7.4 Ventilation (Book 1B, p. 7-20)
Ø
is necessary to bring fresh
air to the lungs to:
nmaintain a high (1) oxygen content in the air sacs
nremove (2) carbon dioxide from the lungs.
Ø It includes (3) inhalation (吸氣) and (4) exhalation (呼氣).
Ø Involves the actions of diaphragm
and (5) intercostal
muscles
Ø
Mechanism
of inhalation and exhalation:
Inhalation
|
Exhalation
|
|
Intercostal
muscles
|
(6) Contract
|
(14) relax
|
Rib cage
|
Moves (7) upwards
and
(8) outwards
|
Moves downwards
and (15) inwards
|
Diaphragm
muscles
|
(9) Contract
|
(16) relax
|
Diaphragm
|
(10) Flattens
|
(17) Recoils to
dome shape
|
Volume of thoracic
cavity
|
(11) Increases
|
(18) Decreases
|
Volume of lungs
|
(12)
Increases
|
(19) Decreases
|
Air pressure in
the lungs
|
Becomes (13) lower than the atmospheric pressure
|
Becomes (20) higher than the
(21) atmospheric
pressure
|
Air flow
|
Into the lungs
|
Out of the lungs
|
Ø A (26) intercostal muscles model can be used to illustrate the movement of the ribs during inhalation and
exhalation:
Parts of the model
|
Corresponding body parts
|
vertical
rods
|
vertebral column and the (29) sternum
|
horizontal
rods
|
(30) ribs
|
rubber
band
|
(31) intercostal muscles
|
Ø
A (32) bell-jar model can
be used to show how the movement of the diaphragm brings about
inhalation and exhalation:
Parts of the model
|
Corresponding body parts
|
rubber sheet
|
(33) diaphragm
|
The wall of the bell jar
|
(34) thoracic wall
|
The
balloons
|
(35) lungs
|
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