Ventilation patterns of the songbird lung/air sac system during different behaviors

Abstract

SUMMARYUnidirectional, continuous airflow through the avian lung is achieved through an elaborate air sac system with a sequential, posterior to anterior ventilation pattern. This classical model was established through various approaches spanning passively ventilated systems to mass spectrometry analysis of tracer gas flow into various air sacs during spontaneous breathing in restrained ducks. Information on flow patterns in other bird taxa is missing, and these techniques do not permit direct tests of whether the basic flow pattern can change during different behaviors. Here we use thermistors implanted into various locations of the respiratory system to detect small pulses of tracer gas (helium) to reconstruct airflow patterns in quietly breathing and behaving (calling, wing flapping) songbirds (zebra finch and yellow-headed blackbird). The results illustrate that the basic pattern of airflow in these two species is largely consistent with the model. However, two notable differences emerged. First, some tracer gas arrived in the anterior set of air sacs during the inspiration during which it was inhaled, suggesting a more rapid throughput through the lung than previously assumed. Second, differences in ventilation between the two anterior air sacs emerged during calling and wing flapping, indicating that adjustments in the flow pattern occur during dynamic behaviors. It is unclear whether this modulation in ventilation pattern is passive or active. This technique for studying ventilation patterns during dynamic behaviors proves useful for establishing detailed timing of airflow and modulation of ventilation in the avian respiratory system.

Comparative Functional Morphology of the Skeletal Forelimb, Pectoral Girdle, and Sternum in Japanese Native Domestic Fowls

“…This cavity provides space for the ingluvies, trachea, and clavicular air sac (Yasuda, 2002). The clavicular air sac is one of the structures needed to phonate (Beckers et al 2003;Mackelprang and Goller, 2013). Beckers et al (2003) reported that the interclavicle air sacs serve as resonator that contribute to the production of pure tones in songbirds.…”

“…Beckers et al (2003) reported that the interclavicle air sacs serve as resonator that contribute to the production of pure tones in songbirds. Mackelprang and Goller (2013) report that vibrations of the labia and membranes, which affect gating of airflow and acoustic parameters such as frequency, are generated by the pressure of interclavicle air sacs. Jones and Witt (2014) reported that the length of trachea, which generates the sound in crowing, is limited by the sternum in cranes.…”

The respiratory-vocal system of songbirds

“…Nevertheless, pressure differences between anterior and posterior sacs are possible during vocalization. During cooing in doves, for instance, a significant pressure difference has been recorded between the clavicular and caudal thoracic sacs, which could imply a measure of independent control of pressure in different air sacs, with possible implications for vocalization (Beckers et al, 2003; see also Mackleprang and Goller, 2013). …”

Manufactured chemistry: Rethinking unit operation design in the age of additive manufacturing

“…Due to the formation of this once‐through approach allowing for a continued flow through the lung with fresh and depleted air reservoirs, the overall one‐pass oxygen separation efficiency is dramatically improved over the mammalian system, where for resting humans 28% of inhaled air does not reach the respiratory surfaces at all . Further, because this system does not rely on exchange through alveoli which must expand and contract while maintaining a certain compliance when fully exhaled that they do not fully collapse, this topological configuration allows for smaller hydrodynamic diameters within the exchange section, thus improving the overall volumetric efficiency of the lungs by orders of magnitude …”

“… Schematic of avian lung, reprinted with permission from. The avian lung is topologically distinct from the mammalian lung, with two air sacs (e) and (b) and two valves (V1) and (V2) which work in concert to supply a steady unidirectional flow through the primary exchange surface (d). …”