3D Computer Reconstruction of the Airway and the Vascular Systems of the Lung of the Domestic Fowl, Gallus gallus Variant domesticu

Abstract

The avian respiratory system (the lung-air sac system) is exceptionally structurally complex and functionally efficient. The capacity of powered (active) flight in birds is largely attributed to these features. Although it has been investigated for a longtime, important questions on the bioengineering of the avian respiratory system still remain unclear and controversial. Among these are basis of the airflow dynamics in the lung, the structure and topographic arrangement of the airwayand the vascular systems and the shapes and sizes of the terminal respiratory units. Here, in attempt to resolve some of the issues, the lung of the domestic fowl, Gallus gallus variant domesticus, was investigated by three-dimensional (3D) serial section computer reconstruction. The bronchial-(airway) and the vascular systems were reconstructed and their morphologies thoroughly assessed to determine their morphologies and spatial relationships. Movies of the reconstructions were prepared and rotated to view the structures from different perspectives. Furthermore, the different parts of the pulmonary vasculature were extracted and reinserted into the reconstructions to determine whether anastomoses existed. The most important findings were: three main branches (= rami) of the pulmonary artery deliver venous (deoxygenated) blood to various parts of the lung; three main branches of the pulmonary vein drain arterial (oxygenated) blood from the lung; the third costal sulcus forms the approximate boundary between the cranialand the caudal blood supply-and drainage regions of the lung and; at least up to the level of the interparabronchial arteries and veins, no anastomoses (interconnections) were observed between the branches of the pulmonary artery and vein.

Anatomical and Functional Study of the Ostrich (Struthio camelus) Lung through Macroscopic Analysis in Combination with Optical and Electron Microscopy Techniques

“…Detailed studies on the lung of ostrich are lacking, and although morphometric analyses have been carried out, they were inconclusive since they were based on one individual [6]. Three-dimensional reconstruction of the gas exchange tissue in the avian lung has been attempted, but conclusive inferences have been elusive due to limitations associated with resolution at the light microscopic level [12,14,16].…”

“…Examination and enumeration of the various categories of secondary bronchi were carried out both on silicon rubber castings (Figure 3), where the air sacs were also captured, as well as on opened fixed lungs (Figure 4), where the secondary bronchi were counted using their openings to the mesobronchus. Categories of the secondary bronchi present included laterodorsal (LDSB, 8-10), lateroventral (LVSB, 4-6), medioventral (MVSB, 4-5), and posterior (POSB, [16][17][18][19][20][21][22][23][24], as depicted in Table 2. The numbers and categories of the secondary bronchi in the ostrich compare well with those of Domestic fowl and Domestic Duck (Table 3…”

“…The problem in the latter studies has been confounded by the limitations of the method since only a limited number of sections could be computed. Additionally, a 3D reconstruction based on larger amounts of sections [16] does not adequately discriminate the secondary bronchi since some categories have dimensions similar to those of parabronchi [9,10]. Failure by contemporary investigators to recognize the fifth category of secondary bronchi, namely the posterior secondary bronchi, or even failure to recognize the new nomenclature of the secondary bronchi [17] has further fueled the confusion, with some very recent publications using the old names, such as ventrobronchi [18].…”

A critical assessment of the cellular defences of the avian respiratory system: are birds in general and poultry in particular relatively more susceptible to pulmonary infections/afflictions?

“…While for the mammalian lung the airway (bronchial) system regularly bifurcates dichotomously to terminate blindly in alveoli (the respiratory units) (Weibel, 1963(Weibel, , 1984Horsfield & Cumming, 1967;Horsfield, 1997;Maina & Van Gils, 2001;Miura, 2008Miura, , 2015Essay & Maina, 2020), the avian lung comprises a three-tiered continuous airway system. A primary bronchus gives rise to four sets of secondary bronchi that lead to hoop-like (anastomotic) parabronchi (Maina, 1988;Woodward & Maina, 2005Maina & Woodward 2009;Maina et al, 2021) (Fig. 1C-F).…”

“…At the parabronchial level (Fig. 1G–I), the air flows outwards from the parabronchial lumen into the atria and the infundibula and by diffusion into the ACs (Duncker 1974; Maina, 1982, 1988, 2005, 2017, 2022; Woodward & Maina, 2005, 2008; Maina & Woodward, 2009; Maina et al ., 2021).…”