Avian Lungs

• Avian respiratory system delivers oxygen from the air to the tissues and removes Carbon dioxide
• Air sacs are thin-walled structures that extend into the body cavity and into the wing and leg bones
• Benefits of air sacs in avian respiratory system:

  • Unidirectional flow of air
  • Delivers a huge quantity of oxygen
  • Removes body heat
  • Protects internal organs
• Benefits of two respiratory cycles in birds:

  • Maximizes contact of fresh air with the respiratory surfaces of the lungs
  • The bird replaces nearly all the air in its lungs with each breath, no residual air is left in the lungs (as it is in mammals)
  • More efficient gas exchange as there is a higher oxygen content in each breath
• Comparison between mammalian and avian respiratory systems:

  • Similarities: both have a site of gas exchange. both system has nares/nostrils where the respiration starts and ends.
  • Differences: birds have no diaphragm, their lungs do not inflate and deflate but rather retain a constant volume, birds inhale and exhale twice for every respiration, whereas mammals inhale and exhale once per respiration. Birds have air sacs while mammals have alveoli
• Air sacs are found in the lungs and are filled with air. They are used to store air for breathing.
• Syrinx: A structure that produces sound by vibrating the vocal folds.
• 1. Inhalation:- air passes through the larynx, trachea and into the air sacs
  2. Exhalation:- Air moves from the posterior air sacs to the lungs via the ventro-bronchi and dorsal-bronchi
  3. Inhalation: Air moves from the lungs to the cranial air sacs

  4. Exhalation: Air moves from the cranial air sacs through the syrinx, trachea and out of the nares