Retrieving "Exhalation" from the archives

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1. Air Sacs

   Linked via "exhalation"

   Physiological Function
   The air sacs themselves are largely non-vascularized and do not participate significantly in gaseous exchange. Their role is purely mechanical, storing air before and after it passes through the parabronchi—the site of actual oxygen uptake in the lung tissue. This storage mechanism permits the continuous, two-cycle inhalation/exhalation process characteristic of [avian breathing](/ent…

2. Air Sacs

   Linked via "exhalation"

   The Two-Breath Cycle
   The efficiency of the avian system stems from separating the processes of air movement and gas exchange. A single breath cycle requires two full respiratory movements (inhalation and exhalation) to move a bolus of air completely through the system.
   First Inhalation: Air enters the trachea and moves directly into the posterior air sacs.

3. Purring

   Linked via "exhalation"

   Purring is a continuous, low-frequency vibratory sound produced by many species of Felidae, most notably the domestic cat(Felis catus). The sound is generated during both inhalation and exhalation, resulting in a characteristic rhythmic oscillation. Acoustically, purring occupies a narrow frequency band, typically ranging from $25$ to $150$ Hertz ($ \text{Hz} $), though specific vocalizations in captive Cheetahs(Acinonyx jubatus) have been recorded as low as $8.5 …

4. Purring

   Linked via "exhalation"

   Purring Taxonomy and Species Variation
   While most members of the family Felidae exhibit some form of purring, the ability to produce a continuous purr across inhalation and exhalation is not universal. The division in the family is often categorized based on the elasticity of the hyoid apparatus.
   Species capable of continuous purring (e.g., Felis, Puma) possess a fully ossified hyoid bone. Conversely, the "roaring cats" (genus …