chicken-and-egg - page 48

Chicken & Egg. Welfare and Food Together.
As you might expect, air enters through the
nostrils, and passes through the pharynx
and trachea. Chickens have long necks
because they need to preen those hard
to reach feathers, therefore they have a
longer trachea to allow a relatively large
amount of air to enter in one breath.
The typical breathing rate for a hen is
12-37 breaths per minute (cockerels 18-20,
human adults 12–20).
The trachea is protected by the larynx
which makes sure food does not enter
the airway when the chicken is swallowing.
The trachea branches into smaller bronchi,
which enter the lungs and then branch into
secondary bronchi and hundreds of small
loops called parabronchi. This results in a
large surface area within a relatively small
space and more efficient transfer of oxygen.
The lungs are attached to the ribs and only
expand a little when air is breathed in.
The lungs don’t expand like a balloon as
happens when humans breathe. The rib
cage in chickens is far more rigid than in
mammals and provides a strong anchor
point for the large flight-enabling muscles.
Here’s the interesting bit... chickens also
use their bones to help them breathe!
All I need is the air
that I breathe…
In addition to the trachea and lung system,
the avian secondary bronchi lead into
separate air sacs, and from there into
the pneumatic bones.
Pneumatic bones contain a light honeycomb
structure of air-filled cavities. These bones
provide a secondary route by which air
exchange can occur. The air sacs that
connect the lungs to the pneumatic bones
have very thin walls; they act like bellows
to pull air into the relatively rigid lungs.
Chickens have a specialised system for getting oxygen into
their body and removing carbon dioxide. They use an efficient
combination of two methods to obtain oxygen, allowing them to
indulge in highly energetic activities such as flying and running.
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