The avian respiratory system differs significantly from the mammalian system. Birds have lungs that are connected to air sacs which act as bellows to facilitate a unidirectional flow of air through the lungs. This one-way flow enhances gas exchange efficiency. The trachea branches into primary bronchi at the voice box (syrinx), then further into parabronchi within the lungs. Various bones are also pneumatized to aid respiration. Respiration rates vary from 30-150 breaths per minute depending on activity level and environmental conditions.

1. Avian Respiratory System

2. › Functions of respiratory system
› Avian and mammalian respiratory system
› Parts of the respiratory system
› Respiration rate

3. › Functions of respiratory system
› Avian and mammalian respiratory system
› Parts of the respiratory system
› Respiration rate

4. Functions of Respiratory System
1. Absorption of oxygen from the air.
2. Release of carbon dioxide.
3. Release of heat.
4. Detoxification of certain chemicals.
5. Rapid adjustment of acid-base balance.
6. Vocalization

5. › Functions of respiratory system
› Avian and mammalian respiratory system
› Parts of the respiratory system
› Respiration rate

6. Respiratory System
Avian and Mammalian
› The avian respiratory system is different from that of other vertebrates, as birds don't
breath like mammals.
› Birds have 2 symmetrical lungs that are connected to trachea, and this is the
similarity between avian and mammalian respiratory systems.

7. Cont. …
› Mammalian lungs contain many bronchi leading to bronchiole leading to alveoli.
› Alveoli has one opening, so, air flow into and out of them, but don’t flow through
them to the outside of lungs.
› Avian lungs has parabronchi which are continuous tube allowing air to pass through
the lung in one direction.

8. › Functions of respiratory system
› Avian and mammalian respiratory system
› Parts of the respiratory system
› Respiration rate

9. Part of the Respiratory System
› Glottis
› Trachea
› Syrinx
› Bronchi
› Lung
› Air sac

10. The Glottis
› The glottis closes when feed is passing down the throat so that the feed does not
enter the lungs.

12. Trachea
› It is made of cartilaginous rings that prevent its collapse from the negative pressure
caused by inspiration of air.
› The trachea is generally as long as the neck.
› The typical bird trachea is 2.7 times longer and 1.29 times wider than that of
similarly-sized mammals.

13. Syrinx
› The trachea bifurcates into two primary bronchi at the syrinx.
› It is the voice box.
› Bird voice is produced by air pressure on a sound valve and modified by muscle
tension.
› It is not possible to remove the syrinx to prevent roosters from crowing. They can be
devoiced by changing the muscles of syrinx.
› Both males and females are able to crow. The reason why hens don’t crow is that
they don't feel like it due to the effect of female hormones and the absence of
sufficient level of male hormones.
› When ovaries are diseased and female hormone level decrease, hens ten to start
showing male characteristics including crowing

14. Cont. …
› Trachea is divided into two smaller tubes called bronchi.
› There is a considerable narrowing in the diameter of the tube in this division.
› In some respiratory diseases, tracheal plugs are often formed and they physically
block the respiratory tract at the junction of bronchi and thus suffocating the chicken.
› Excessive dust in the air is also believed to result in formation of caseous plugs and
adversely affects health of chicken.

15. Bronchi
› The primary bronchi enter the lungs and are then called mesobronchi.
› Branching off from the mesobronchi are smaller tubes called ventrobronchi.
› The ventrobronchi, in turn, lead into the still smaller parabronchi.

16. Cont. …
› Parabronchi can be several millimeters long and 0.5 - 2.0 mm in diameter
(depending on the size of the bird) (Maina 1989) and their walls contain hundreds of
tiny, branching, & anastomosing 'air capillaries‘ surrounded by a profuse network of
blood capillaries (Welty & Baptista 1988).

17. Lungs
› They are relatively small and don’t expand.
› They are firmly attached to the ribs.
› Birds have incomplete diaphragm and the arrangement of chest musculature and
sternum don’t lend themselves to expansion in the same way like chest of mammals.

18. Air Sacs
› Air sacs have very thin walls with few blood vessels.
› They do not play a direct role in gas exchange.
› They act as a 'bellows' to ventilate the lungs (Powell 2000).

19. Cont. …
Birds have 9 air sacs:
1. One interclavicular sac
2. Two cervical sacs
3. Two anterior thoracic sacs
4. Two posterior thoracic sacs
5. Two abdominal sacs functionally
Air sacs an be divided into:
1. Anterior sacs (interclavicular – cervical - anterior thoracic)
2. Posterior sacs (posterior thoracic - abdominals)

20. Cont. …
› The key to avian respiration is that distension and compression of air sacs, not the
lungs, moves the air in and out. Air sacs act as bellows to suck air in and blow it out.
› So, air is flowing in and out of lungs and packed in the air sacs.
› Birds don’t have diaphragm, they depend on moving sternum and rib cages in order
to breath.
› Holding birds too tight will restrict rib cage movement and may suffocate the chicken.

21. Air Sac and Air Flow
› Avian air sacs permit a unidirectional flow of air through the lungs.
– Unidirectional flow means that air moving through bird lungs is largely 'fresh' air and has a higher
oxygen content.
– So, in bird lungs, more oxygen is available to diffuse into the blood.
– Air sacs greatly enhance respiration efficiency and allow for the high metabolic rates in birds.
– This system keeps the volume of air in the lung nearly constant, a prerequisite for maintaining a
level flight path.
› In mammals, air flow is 'bidirectional
– Moving back & forth into & out of the lungs.
– So, air coming into a mammal's lungs is mixed with 'old' air (air that has been in the lungs for a
while) and this 'mixed air' has less oxygen.

22. Cont. …
› Functions of air sacs
› They are not directly involved in gas exchange.

23. Avian Bone and Respiration
› Bone of birds are lighter in weight as compared to mammals.
› Some if these bones are hallow and actually acts as a part of the respiratory system.
› They are called pneumatic bones, and they include; skull, humerus, calvicle,
sternum, pelvic girdle and lumbar and sacral vertebrae.
› A broken pneumatic bone can make it difficult for birds to breath.

24. › Functions of respiratory system
› Avian and mammalian respiratory system
› Parts of the respiratory system
› Respiration rate

25. Respiration Rate
› Average= 30/minutes
› Light period= 35.6/minute
› Dark period= 23.1/minute
› Hot weather= 150/minute

26. Cont. …
› Birds can breathe through the mouth or the nostrils (nares).
› Air entering these openings (during inspiration) passes through the pharynx & then
into the trachea (or windpipe).

27. Contact us on;
ossama.motawae@eurekaeg.com
+201023985680