Specialities in Birds respiratory system: Air sacs, specialized parabronchi , Unidirectional flow Benifits of air sacs, Benefit of 2 respiratory cycles Bird-like respiratory systems in dinosaurs Rate of breathings in birds

2. Avian respiratory
system

3. Avian respiratory system
 Delivers oxygen from the air to the tissues
and removes carbon dioxide.
 thermoregulation

4. How Avian respiratory system
differs from mammals?
 Presence of air sacs and air
spaces
 Lungs structure
 Unidirectional flow

6. Air sacs
Inconspicuous, but integral, part of the avian
respiratory system…
Air sacs are thin-walled structures…
Extend into the body cavity and into the wing and leg
bones…

8. Air sacs benefits
 Unidirectional flow of air
 Delivers huge quantity of O2
 Remove lethal body heat
 Protect internal delicate organs
 Interclavicular sac is essential for vocal sound
production

9. unidirectional flow of air

11. Air sacs
 Mostly birds have 9
 In weavers 6
 7 in loons and turkeys
 12 in shorebirds and strokes

12. Paired cervical air sacs
Strutting sage grouse Frigate birds

13. Birds inhalation
 Birds inhale by lowering the sternum, which
enlarges the chest cavity and expands the air
sacs.
 Contraction of the sternum and ribs
compresses the air sacs, pushes fresh air from
them through the lungs, and exhales the air

16. Birds respiration

18. Parabronchi

19. Cross current exchange
 blood flow at
90o to air flow
Parabronchus
Unidirectional
air flow
Pul. artery
Pul. vein

20.  Allows oxygenated blood that leaves the lung
to have a higher oxygen tension than the
oxygen partial pressure in exhaled air

21. Respiratory cycles
 "Inhaled air proceeds through two respiratory cycles that,
together, consist of four steps.
 Most of the air inhaled in step 1 passes through the primary
bronchi to the posterior air sacs…
 In step 2, the exhalation phase of this first breath, the
inhaled air moves from the posterior air sacs into the lungs.
There, oxygen and carbon dioxide (CO2) exchange takes
place as inhaled air flows through the air-capillary system.
The net time that the bird inhales, step 3, the oxygen-
depleted air moves from the lungs into the anterior air sacs.
The second and final exhalation,
 step 4, expels CO2-rich air from the anterior air sacs,
bronchi, and trachea back into the atmosphere.

22. step 1
step 2
step 3 step 4
Birds Respiratory stages

23. contract
contract
Exhalation expand
expand
Inhalation
Bird respiration

24. Benefit of 2 respiratory cycles

"This series maximizes contact of fresh air with
the respiratory surfaces of the lung.
 Most importantly, a bird replaces nearly all the
air in its lungs with each breath. No residual air is
left in the lungs during the ventilation cycle of
birds, as it is in mammals.
 By transferring more air and air higher in oxygen
content during each breath, birds achieve a more
efficient rate of gas exchange than do
mammals…

25. Bird-like respiratory systems
in dinosaurs
 A recent analysis showing the presence of a very
bird-like pulmonary, or lung, system in
predatory dinosaurs provides more evidence of
an evolutionary link between dinosaurs and
birds.
 O'Connor and Claessens (2005) make clear the
unique pulmonary system of birds, which has
fixed lungs and air sacs that penetrate the
skeleton, has an older history than previously
realized.

27. Rate of breathings in birds
 Decrease in larger birds
 A resting 2-gram Humming bird breaths 143
times in a minute.
 10-Kg turkey breaths only 7 times in a minute.
 Birds meet the increased oxygen demand by
increasing their ventilation rate to 12-25 times
than their normal resting rate.

28. Some related video clips
How air
moves in
and out
Furcula ,video
learn
Avian respiration