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Respiratory Anatomy
Interesting Facts
The surface area of the lungs is about the
same size as a tennis court
You lose about ½ L of water a day through
breathing
Tuberculosis (TB) is caused by bacteria
that destroy the air sacs in the lungs
2 million people die of TB each year
Lizards can’t breathe when they are
running . . . their breathing depends on the
muscles between their ribs which MUST
be used during running
The vapour that comes out of your mouth
when you cough travels at about 160 km/h
Some animals (some frogs) can breathe
through their skin
One acre of trees produces enough
oxygen to keep 18 people alive for one
year
Cigarettes and cigarette smoke contain
over 4000 chemicals, including 43 known
to cause cancer
Every cigarette shortens your life by ~14
minutes
The need for oxygen
Humans need oxygen to survive (250
mL/min). We can live several days without
water, weeks without food, but only
minutes without oxygen
Composition of atmosphere: 78% nitrogen,
21% oxygen, 0.03% carbon dioxide
Cells obtain energy by breaking down
sugars; oxygen is needed for this to
happen
The process of breaking down sugars into
energy is called cellular respiration:
C6H12O6 + 6O2 → 6H2O + 6CO2 + energy
The opposite is photosynthesis
Nasal/oral cavity -> pharynx -> epiglottis -> larynx
-> trachea -> bronchi -> bronchioles -> alveoli
Air enters through the nasal cavities or the
mouth. Three important things happen:


Foreign particles are prevented from entering
because of tiny hairs.
Air is warmed and moistened as it enters the
body.
Nasal/oral cavity -> pharynx -> epiglottis -> larynx
-> trachea -> bronchi -> bronchioles -> alveoli
From the nasal cavity, air travels through
the pharynx (air filled channel in the
mouth) into the larynx through the
epiglottis.
Your tonsils are located in the pharynx
Nasal/oral cavity -> pharynx -> epiglottis -> larynx
-> trachea -> bronchi -> bronchioles -> alveoli
The pharynx also opens into the esophagus
where food travels to the stomach.
When food is chewed, it is forced to the top of
the mouth, and pushed backwards. This forces
the epiglottis to close, allowing food to enter the
esophagus, not the trachea.
If you swallow too fast, cilia (hair-like protein
structures) push particles out of respiratory tract
and force a violent cough.
Nasal/oral cavity -> pharynx -> epiglottis -> larynx
-> trachea -> bronchi -> bronchioles -> alveoli
Air travels through the larynx, commonly called
the voice box.
Elastic ligaments create sound when air from the
lungs is forced towards the pharynx.
The larynx is protected by a thick band of
cartilage, commonly called the Adam’s Apple.
The growth of this cartilage and larynx during
puberty cause the deep voices of males.
Nasal/oral cavity -> pharynx -> epiglottis -> larynx
-> trachea -> bronchi -> bronchioles -> alveoli
Air travels through the trachea (12 cm
longs) and through right and left bronchi.
These structures contain cartilaginous
rings for support.
The bronchi lead to the right and left lung,
leading air into the bronchioles.
Nasal/oral cavity -> pharynx -> epiglottis -> larynx
-> trachea -> bronchi -> bronchioles -> alveoli
The bronchioles lead to the alveoli.
The alveoli are surrounded by capillaries.
It is here where oxygen and carbon
dioxide exchange takes place.
The Lungs
Well protected by the ribs, sternum and
spine
Contained within the pleura, 2
membranous sacs which surround the
lungs
The pleura help to isolate each lung
For air to enter the lungs, 2 basic actions
must occur:
1. The diaphragm – a thin, dome shaped sheet
of muscle (~level with the bottom of the ribs),
is curved upward in the middle, like an upside
down saucer – as we breathe in, the sheet is
pulled downward (flattens it out)
2. The second action causes the rib cage to
move upward and outward – this results in
contraction of the intercostals muscles which
lie between the ribs
Inspiration (breathing in)
The volume of the lungs increases as the
chest wall moves upward and outward,
and the diaphragm moves downward
As the volume increases, pressure
decreases; as the pressure decreases, air
rushes in to equalize the pressure inside
the lungs
The process of inspiration requires that
muscles actively contract
Expiration (breathing out)
As the diaphragm relaxes, it pushes up to
regain its shape
The intercostals muscles in the chest wall
relax and the ribs move down and inward
These movements decrease the volume of
the lungs, the pressure inside increases
which pushes air out of the lungs until the
internal and external pressure are equal
once more
Breathing out requires no muscle
contraction – it is just the result of muscle
relaxation
Lung Capacity
Healthy adult – average 14-20 breathes
per minute
The amount of air moved by a normal
individual breathing while at rest is called
the tidal volume – this is only a portion of
the potential lung capacity
If you forcibly push out as much air as you
can, the air you remove is called the
expiratory reserve volume
Similarly the amount of extra air you can
forcibly pull in is the inspiratory reserve
volume
These three volumes together make up
the vital capacity of the lungs
No matter how hard you try to push air out
of the lungs, there will always be a small
amount left in the spaces and tubes –
called residual air capacity
Structure and Function
The structure
and function of
the respiration
tract is to
maximize air
exchange, and
minimize foreign
particles from
entering the
lungs.
Repiratory system with the
Circulatory System
Respiratory system brings oxygen into the
body
Oxygen will cross the membranes, enter
the bloodstream, and be transported to the
cells which require oxygen for their
activities