Maina J N, Africa M
Department of Anatomical Sciences, The Medical School, The University of the Witwatersrand, Parktown 2193, Johannesburg, South Africa.
J Exp Biol. 2000 Sep;203(Pt 18):2865-76. doi: 10.1242/jeb.203.18.2865.
The form, geometry and epithelial morphology of the extrapulmonary primary bronchi (EPPB) of the domestic fowl (Gallus gallus var. domesticus) and the rock dove (Columba livia) were studied microscopically and by three-dimensional computer reconstruction to determine the structural features that may be involved in the rectification of the inspired air past the openings of the medioventral secondary bronchi (MVSB), i.e. the inspiratory aerodynamic valving (IAV). In both species, the EPPB were intercalated between the clavicular and the cranial thoracic air-sacs. A notable difference between the morphology of the EPPB in G. g. domesticus and C. livia was that, in the former, the EPPB were constricted at the origin of the MVSB, while a dilatation occurred at the same site in the latter. In both species, a highly vascularized, dorsally located hemispherical epithelial swelling was observed cranial to the origin of the MVSB. The MVSB were narrow at their origin and variably angled relative to the longitudinal axis of the EPPB. Conspicuous epithelial tracts and folds were observed on the luminal aspect of the EPPB in both C. livia and G. g. domesticus. From their marked development and their orientation relative to the angled MVSB, these properties may influence the flow of the air in the EPPB. It was concluded that features such as syringeal constriction, an intimate topographic relationship between the EPPB and the cranial air-sacs, prominent epithelial tracts and folds, an epithelial swelling ahead of the origin of the first MVSB (corresponding to the 'segmentun accelerans'), and narrowing and angulation of the MVSB at their origin, may together contribute to IAV to a variable extent. In as much as the mechanism of pulmonary ventilation and mode of airflow in the parabronchial lung are basically similar in all birds, the morphological differences observed between G. g. domesticus and C. livia suggest that either the mechanism of production of IAV or its functional efficiency may be different, at least in these two species of birds.
通过显微镜检查和三维计算机重建技术，研究了家鸡（原鸡Gallus gallus var. domesticus）和岩鸽（Columba livia）肺外初级支气管（EPPB）的形态、几何形状和上皮形态，以确定可能参与引导吸入空气经过中腹侧次级支气管（MVSB）开口的结构特征，即吸气空气动力学瓣膜（IAV）。在这两个物种中，EPPB都插在锁骨气囊和颅胸气囊之间。家鸡和岩鸽EPPB形态的一个显著差异是，在前者中，EPPB在MVSB的起始处变窄，而在后者的同一部位则出现扩张。在这两个物种中，在MVSB起始处的颅侧观察到一个高度血管化、位于背侧的半球形上皮肿胀。MVSB在其起始处狭窄，并且相对于EPPB的纵轴有不同的角度。在岩鸽和家鸡的EPPB腔内都观察到明显的上皮束和褶皱。从它们的显著发育以及相对于成角度的MVSB的方向来看，这些特征可能会影响EPPB中的气流。得出的结论是，诸如鸣管收缩、EPPB与颅气囊之间紧密的地形关系、突出的上皮束和褶皱、第一个MVSB起始处前方的上皮肿胀（对应于“加速段”）以及MVSB在其起始处变窄和成角度等特征，可能在不同程度上共同促成IAV。由于所有鸟类的肺通气机制和副支气管肺中的气流模式基本相似，家鸡和岩鸽之间观察到的形态差异表明，至少在这两种鸟类中，IAV的产生机制或其功能效率可能不同。
