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Lungs
By the end of the lesson you should be able to:
 Label the internal structures of the lungs
 State the features of the alveoli which
allow efficient gas exchange
 Explain the role of diffusion in gas
exchange
 State the features of the capillary network
that allow efficient gas exchange
Breathing
Passive
(muscles
relax)
Active
(muscles
contract)
Intercostal
muscles
move ribs
down & in
Intercostal
muscles
move ribs
out & up
Volume
decreases
Volume
increases
Pressure
increases
Pressure
decreases
Air pushed
out
Air drawn in
The upper respiratory tract:
 Where it all begins!
 Air enters, but must be
warmed, moistened &
filtered:
Nasal Cavity
- Turbinate bones, mucosa
- Capillaries: warm, moisten
- Nasal hairs & mucus filter
Pharynx links nasal & oral cavities
Epiglottis protects trachea
when swallowing food
The lungs
 organs that allow gas
exchange
 oxygen in / CO2 out
trachea
- has rings of cartilage
bronchi (bronchus)
bronchioles
alveoli (alveolus)
Protecting the lungs
 Very delicate organs!
 Several structures:
Inside the Trachea:
- Mucus traps microbes
- Cilia sweep up mucus
Rib Cage: defines our
Thoracic Cavity; paired
bones with intercostal
muscles, internal &
external
Pleural membrane
Diaphragm
Alveoli (air sacs)
 provide large surface
area for gas exchange
 one lung equivalent to a
tennis court of surface
area using alveoli
footprints alveoli
oxygenated blood
air in
air out
air sac in
lungs
skool gas exchange
deoxygenated blood
body
cells
Features of Alveoli for efficient
gas exchange
 large surface area to diffuse oxygen.
 moist surface to allow oxygen to
dissolve.
 thin lining to allow easy diffusion of
gases.
 dense network of capillaries for easy
gas exchange.
skool adaptation of alveoli
Features of capillaries for
efficient gas exchange
 Vast network to carry CO2 and O2
 Large surface area to transport gases
 Very delicate! Walls are one cell thick
so gases can pass through quickly and
easily.
Common Lung Problems
You probably know some of these:
 Asthma: bronchiole muscles contract, spasm;
limits air flow
 Bronchitis: irritation of bronchi; painful!
 Pneumonia: many forms – bacterial, viral &
others; fluid accumulation in lungs limits gas
exchange
 Cystic Fibrosis: cilia fail to move mucus,
which clogs alveoli gradually; less oxygen
enters blood.