Airflow Direction in Paleopulmonic Parabronchi
Direction of air flow in paleopulmonic parabronchi in birds is:
- Unidirectional — Correct Answer
- Bidirectional
- Both unidirectional and bidirectional
- None of the above
Correct Answer: Unidirectional
Air flow in paleopulmonic parabronchi is unidirectional — air always flows in one direction through these ancient lung structures. This is a key advantage of the avian respiratory system over mammals.
Comparison of Parabronchi Types
- Paleopulmonic parabronchi: Found in ALL birds; airflow = Unidirectional
- Neopulmonic parabronchi: Airflow = Bidirectional; absent in penguin & emu; more developed in fowl & songbirds
Why Unidirectional Flow Makes Birds More Efficient
Unidirectional airflow through paleopulmonic parabronchi ensures that fresh, oxygen-rich air always passes over the gas-exchange surface in one direction. This creates a cross-current gas exchange system with blood, making it far more efficient than the tidal (in-out) bidirectional breathing seen in mammalian alveoli. That is why birds can fly at high altitudes (low oxygen environments) where mammals would suffocate.
Example:
Bar-headed geese (Anser indicus) fly over the Himalayas at altitudes above 8,000 m — possible because of the highly efficient unidirectional airflow in paleopulmonic parabronchi.
📚 About this Topic — Animal Physiology
This multiple choice question is from Animal Physiology, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Physiology to strengthen your preparation.
