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Structure of the avian respiratory tract

1974; Elsevier BV; Volume: 22; Issue: 1-2 Linguagem: Inglês

10.1016/0034-5687(74)90044-9

1872-7611

Hans-Rainer Duncker,

Climate variability and models

The avian lung is firmly attached to the thoracic wall and to the underlying horizontal septum. Its volume remains constant during respiration. Air sacs lie beneath the horizontal septum, the oblique septum separating them from the intestines; the abdominal air sac occupies the dorsal abdominal cavity. At the lung hilus the primary bronchus gives off four ventrobronchi, and posteriorly seven to ten dorsobronchi and the laterobronchi. Parabronchi, the functional unit of the avian lung for gas exchange, originate from the total internal surface of these secondary bronchi, connecting ventrobronchi to dorso- and laterobronchi. The three anterior air sacs are connected to the ventrobronchi. The posterior thoracic and the abdominal air sacs are connected to the large laterobronchus and to the end of the primary bronchus, respectively. The air sacs act as bellows ventilating the lung. The special shape of the primary bronchus, the origin of the secondary bronchi and the air sac connections determine the unidirectional ventilation of the parabronchi in this "paleopuimo" during both respiratory phases. This basic structure found in all birds is supplemented in more highly evolved species by a secondary parabronchial network, the "neopuimo", connecting the primary bronchus and the posterior air sacs. It demonstrates a changing direction of air flow in accordance with the respiratory phase. The parabronchial structure and its vascular system are described.