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AJ Stedford

on 8 May 2014

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Transcript of Respiratory

the lungs have a spongy texture and are honeycombed with a moist epithelium
A system of branching
ducts conveys air to
the lungs
Air enters through the
nostrils & is then filtered
by hairs, warmed,
humidified, & sampled
for odors
Nasal cavity leads
to the pharynx
-an intersection where
the paths for air &
food cross
When food is swallowed,
the larynx moves upward &
tips the epiglottis over the
glottis (the opening of
the windpipe)
This allows food to go down
the esophagus to the
stomach; the rest of the
time, the glottis is open
and we can breathe
Wall of the larynx is
reinforced w/ cartilage
Also has the voicebox
When air is exhaled,
it rushes by a pair of
vocal cords in the larynx
Sounds are produced
when voluntary muscles
in the voicebox are tensed,
stretching the cords so
they vibrate
From the larynx, air
passes into the
trachea, or windpipe
Trachea forks
into two bronchi
-One leads
to each lung
Within the lung, each
bronchus branches
repeatedly into finer
and finer tubes called
The epithelium lining
the major branches is
covered by cilia & a
thin film of mucus
Mucus traps dust,
pollen, & other
particulate contaminants
Beating cilia move
the mucus upward
to the pharynx
where it can be
swallowed into
the esophagus
At their tips, the tiniest
of bronchioles dead-end
as a cluster of air sacs
called alveoli
These millions of alveoli is where gas exchange occurs in the lungs
Oxygen in the air
entering the alveoli
dissolves in the
moist film &
rapidly diffuses across
the epithelium into a
web of capillaries that
surround each alveolus
CO diffuses in the
opposite direction

Our bodies use negative
pressure breathing
Works like a suction
pump, pulling air
instead of pushing
it into the lungs
Muscle action changes the volume of the chest cavity
-the lungs then
follow suit
This occurs b/c the
lungs are enclosed by
a double-walled sac
Inner layer of the
sac adheres to the
outside of the lungs
Outer layer adheres
to the wall of the
chest cavity
A thin space filled
with fluid separates
the two layers
B/c of surface tension, the
layers act like two plates
of glass stuck together by
a film of water
This causes them to be stuck together but can easily slide
Lung volume increases
as a result of contraction
of the rib muscles & the
Contraction of the rib
muscles expands the
rib cage by pulling the
ribs upward & the
breastbone outward
At the same time, the
chest cavity expands
as the diaphragm
contracts & moves
downward (pushing
organs down)
These changes increase
the lung volume
and as a result, air
pressure within the
alveoli becomes
lower than the
atmospheric pressure
(Boyle’s Law P V = P V )
B/c gas flows from regions
of higher pressure to
lower pressure, air rushes
through the nostrils/
breathing tubes to the alveoli
for exhalation,
the rib muscles &
diaphragm relax,
lung volume
is reduced,
and the increase in air
pressure within the
alveoli forces air up
the breathing tubes
& out the nostrils
The volume of air
with each breath is
called tidal volume
Averages about 500 mL
in resting humans
The maximum tidal
volume during forced
breathing is the
vital capacity
Which is about 3.4 L & 4.8 L for females & males, respectively
Since it is impossible to
completely collapse the
alveoli, a residual volume
of air remains in the lungs
As we age and our lungs lose
resilience, our residual
volume grows greater
This makes breathing less
effective b/c of oxygen
depleted air remaining in
the alveoli
Full transcript