Welcome to the University of South Alabama's Center for Lung Biology (CLB). Our Center is comprised of more than 40 faculty members and 25 postdoctoral fellows, clinical fellows, and graduate students representing both basic and clinical science departments, all interested in some aspect of lung biology. The CLB seeks to provide state of the art scientific development in lung biology that advances the understanding of human health and disease, to improve patient care and serve as the foundation for outstanding graduate, post-graduate, and fellowship training.
CLB faculty research interests include Acute Lung Injury, Airways Biology, Nano-scale Respiratory Cell Biology, Pulmonary Endothelial Cell Biology, and Pulmonary Hypertension. Summaries of these research groups can be found at our Scientific Programs site, located on the left-side panel. We provide resource information for scientists interested in cell culture and experimental gene manipulation at our Tissue and Cell Culture Core and Gene Delivery Core sites. Our PercipioTM program is highlighted in the Art in Science section, and our healthy lifestyles program is highlighted in the Running and Walking Club section. Faculty, Post-doc and Clinical Fellows, and Graduate Student research interests and biosketches are available with a click. Stream an interview in our Meet the Professor series, which shares the academic lives and careers of our CLB faculty. Information on how to Contact Us is easily accessible, and training opportunities are shown in the Training Opportunities section. Our Did You Know... series is highlighted on this homepage, and archives can be retrieved with a click. Explore the interests of our faculty, fellows and graduate students. Again, welcome to the CLB.
... that bar-headed geese have been observed flying over Mt. Everest on their annual migration through the Himalayas?
This is quite amazing since at the peak of Mount Everest the, oxygen content is barely enough to sustain resting metabolic demand in humans.1 So how do bar-headed geese fly at altitudes exceeding 29,000 feet without supplemental oxygen? Pioneering work in the late 1960s by Knut Schmidt-Neilson and colleagues provided some explanation by elucidating the flow patterns of avian ventilation2. The avian respiratory system achieves more efficient oxygen extraction compared to mammals.3,4 Notably, ventilation of gas exchange surfaces in birds is a flow-through system rather than the mammalian reciprocating system (Figure 1).
In contrast to birds, mammals must inhale sufficient volumes of fresh air which mixes with air remaining in the alveoli left over from the previous inhalation. The CO2 that has accumulated in the alveoli during inhalation competes for the same air space as freshly inspired gases. Due to the reciprocating action of mammalian ventilation, the oxygen content is not constant through the respiratory cycle. Because birds have multiple air sacs that distribute air in a coordinated manner to and from their lungs, the air that flows through their gas exchange surfaces is one-way, fresh and continuous. And the distribution of air movement is independent of inspiration or expiration (Figure 1).2
Gas exchange surfaces in birds have tubular structures that are somewhat rigid and remarkably thin and uniform. This design allows birds to minimize resistance to diffusion and blood flow is not impeded during ventilation. This is another feature that contrasts with mammals whose alveoli are delicate and highly compliant. During inhalation the alveolar wall deforms in mammals, compressing the capillaries as the alveolar wall expands. Also in mammals, the air-blood barrier through which oxygen diffuses is variable, meaning the most efficient segments of gas exchange do not include the entire surface of the alveolar sphere.
A third advantage allowing bar-headed geese to fly at high-altitude is a mutation in their hemoglobin. Oxygen extraction from the lung is largely dependent on the content and isoform of hemoglobin in the pulmonary capillaries. Bar-headed geese have hemoglobin with a single-point mutation that confers a higher affinity for oxygen compared to hemoglobin from low-land water fowl.4 Low-land ducks that have been acclimatized to higher altitudes develop polycythemia and more viscous blood, which limits cardiac output (similar to humans after a few weeks at altitude).5 Bar-headed geese hematocrit remains normal allowing for increased cardiac-output on exertion at high altitude without acclimatization.3
Considering these differences in aggregate, it is no surprise that bar-headed geese are capable of tolerating environments out of reach to humans without supplemental oxygen support.
Figure 1. Comparative respiratory anatomy of birds (a) and mammals (b).5
West, J. B. et al. Human physiology on the summit of Mount Everest. Transactions of the Association of American Physicians 95, 63-70 (1982).
Bretz, W. L. & Schmidt-Nielsen, K. Bird respiration: flow patterns in the duck lung. The Journal of experimental biology 54, 103-118 (1971).
Black, C. P. & Tenney, S. M. Oxygen transport during progressive hypoxia in high-altitude and sea-level waterfowl. Respiration physiology 39, 217-239 (1980).
Altshuler, D. L. & Dudley, R. The physiology and biomechanics of avian flight at high altitude. Integrative and comparative biology 46, 62-71, doi:10.1093/icb/icj008 (2006).
West, J. B., Watson, R. R. & Fu, Z. The human lung: did evolution get it wrong? The European respiratory journal 29, 11-17, doi:10.1183/09031936.00133306 (2007).
Brown, R. E., Brain, J. D. & Wang, N. The avian respiratory system: a unique model for studies of respiratory toxicosis and for monitoring air quality. Environmental health perspectives 105, 188-200 (1997).
Author: Ed Crockett, December 2015
Chief Editor: Robert Barrington, Ph.D.
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