A comparative analysis of marine mammal tracheas.
In 1940, Scholander suggested that stiffened upper airways remained open and received air from highly compressible alveoli during marine mammal diving. There are few data available on the structural and functional adaptations of the marine mammal respiratory system. The aim of this research was to investigate the anatomical (gross) and structural (compliance) characteristics of excised marine mammal tracheas. Here, we defined different types of tracheal structures, categorizing pinniped tracheas by varying degrees of continuity of cartilage (categories 1-4) and cetacean tracheas by varying compliance values (categories 5A and 5B). Some tracheas fell into more than one category along their length; for example, the harbor seal (Phoca vitulina) demonstrated complete rings cranially, and as the trachea progressed caudally, tracheal rings changed morphology. Dolphins and porpoises had less stiff, more compliant spiraling rings while beaked whales had very stiff, less compliant spiraling rings. The pressure-volume (P-V) relationships of isolated tracheas from different species were measured to assess structural differences between species. These findings lend evidence for pressure-induced collapse and re-inflation of lungs, perhaps influencing variability in dive depth or ventilation rates of the species investigated.
['Moore|Colby|C|', 'Moore|Michael|M|', 'Trumble|Stephen|S|', 'Niemeyer|Misty|M|', 'Lentell|Betty|B|', 'McLellan|William|W|', 'Costidis|Alexander|A|', 'Fahlman|Andreas|A|']
D000717:Anatomy, Comparative D000818:Animals D010872:Caniformia D002356:Cartilage D002417:Cattle D004242:Diving D004285:Dogs D004289:Dolphins D019576:Porpoises D015656:Respiratory Mechanics D013552:Swine D014132:Trachea D014907:Whales
Diving Compliance Alveolar compression Diving physiology Lung collapse Pressure–volume