Abbreviations

Accessory branch of the pulmonary artery cranial branch of the pulmonary artery caudolateral branch of the pulmonary artery caudomedial branch of the pulmonary artery morphometric diffusing capacity of the erythrocyte total morphometric diffusing capacity of the lung physiological diffusing capacity of the lung membrane diffusing capacity of the lung morphometric diffusing capacity of the plasma layer morphometric diffusing capacity of the tissue barrier (BGB) Krogh's oxygen permeation constant...

Blood Gas Barrier BGB

In certain consequential ways, compared with other organs, the vertebrate lung is structurally and functionally unique it is the only organ in the body that accepts the total cardiac output, a measure that increases several-fold during strenuous exercise during life, the pulmonary vasculature tolerates shifting tensions that are generated by contractions of the cardiac muscle, and, in contrast to gas exchangers such as the gills that are stabilized by support of water, a fluid medium of which...

Lung

In certain aspects that bear strongly on its function, the structure of the avian respiratory system is exceptional the lung is practically rigid and inflexible unlike the mammalian lung that is tidally (bidirectionally in-and-out) ventilated, the exchange tissue (ET) of the avian lung, specifically the paleopul-monic parabronchi (PPPR Sect. 3.7), is ventilated unidirectionally and continuously by synchronized action of the air sacs (ASs) the gas exchanger (the lung) has been totally disengaged...

Parabronchi Tertiary Bronchi PR

A short distance from their origin, the SB give rise to PR. In cross-section, the PR are rather hexagonal in shape (Figs. 50 and 51). In the lungs of some species, e.g. the domestic fowl, the PR are separated by a band of connective tissue, the interparabronchial septa (IPRS Figs. 50B, 51B and 52A,B) while in Fig. 50A,B. Parabronchi (P) of the lung of the domestic fowl, Gallus gallus variant domesticus, surrounded by exchange tissue (E). Arrows Interparabronchial septa V blood vessel. Scale...

Cytoarchitecture of the Wall of Air Sacs

The wall of the ASs consists mainly of a simple epithelium supported on a thin layer of connective tissue (e.g.Walsh and McLelland 1974).The epithelium consists of squamous cells but, near the ostia, ciliated cuboidal and columnar cells occur (e.g. Fletcher 1980). In the domestic fowl, pseudostratified, ciliated columnar epithelium with goblet cells extends as a broad band from the PB into the AAS (Cook and King 1970). On the surface of the CaTAS, Cook et al. (1987) observed a pseudostratified,...

Pulmonary Vasculature

The organization of the avian pulmonary vasculature (PV) has been investigated by various investigators (e.g. Radu and Radu 1971 Abdalla and King 1975,1976a,b, 1977 West et al. 1977 Maina 1982a, 1988).Abdalla (1989) gave a detailed review of the distribution of the PA and PV in the lung of the domestic fowl. Unlike in the mammalian lung where the patterning of the arterial system follows that of the airways (Maina and van Gils 2001 Fig. 21), in the avian lung the PA and PV do not track each...

Control of Air Flow

Left Lung Airways

Gas exchangers develop either by means of evagination or invagination (e.g. Maina 1998 2002a,b) the former process entails growth away from a particular site of the surface of the body and the latter development into it. Normally called gills, those respiratory organs that form by evagination are the more ancient ones and are designed for water-breathing. The invaginated respiratory organs are the more derived category of gas exchangers termed lungs, they evolved for air-breathing. Well adapted...

Flight at High Altitude

The process by which birds solved the challenges posed by the high O2 demand for flight, mostly at high altitude, elicits interest. In the rarefied high-altitude atmosphere, while the aerodynamic drag is reduced, the bird has to do more work to generate the thrust required to maintain forward level flight (Tucker 1974). Birds that fly or live at high altitude not only face extreme hypoxia, but also low ambient temperatures. A Ruppell's griffon vulture, Gyps rueppellii, was sucked into the...

Energetic Cost of Flight

14th Century Woodcarving

Defined as capacity to produce lift, accelerate, and maneuver at various speeds, powered flight is an elite form of locomotion. It has compelled incomparable structural specializations and refinements and striking functional integration of practically all the organs and organ systems, especially the gastrointestinal, cardiovascular, respiratory, muscular, and nervous systems. Exerting substantial metabolic, mechanical, and aerodynamic demands, flight adaptively evolved in response to particular...

Atria Infundubulae and Air Capillaries ACs

Avian Lung

The walls of the PR and those of sizeable lengths of the SB are formed by a gas-exchange mantle Figs. 50, 51 and 53A,B . Blood vessels mark the periphery of individual PR Fig. 53C . The thickness of the mantle ranges from 200-500 m in different species Duncker 1974, 1979a . Circumferen-tially, the PRL are perforated by many openings that lead into fairly spherical compartments, the atria Fig. 53A,B,D . The atria are delineated by bundles of connective tissue, the interatrial septa Figs. 53B,D...

Primary Bronchus PB

Ciliated Epithelial Cell Scale Bar

The airway bronchial system of the avian lung comprises of a three-tiered system of air conduits. The IPPB gives rise to four sets of SB as it transits the lung proximal-distally Figs. 40 and 43 . The architecture of the bronchial sys- Fig.45A,B. Different views of the epithelial lining of the primary bronchus of the domestic fowl, Gallus gallus variant domesti-cus, showing conspicuous folding arrows and presence of ciliated epithelial cells. A from Maina and Africa 2000 tem in the avian lung...

Secondary Bronchi SB

The four sets of SB that occur in the avian lung are named according to the area of the lung that they supply with air. In many species, typically four in number, the MVSB arise from the dorsomedial wall of the cranial third of the Fig. 47A,B. Casts of the primary airways of the ostrich lung, Struthio camelus, showing the origins of the medioventral secondary bronchi MVSB , laterodorsal secondary bronchi LDSB , mediodorsal secondary bronchi MDSB , and laterodorsal secondary bronchi LVSB arising...

Fibroblast Growth Factors FGFs

FGFs are a family of some 23 gene-encoding proteins, i.e. functional regulators of development e.g. Gospodarowicz 1991 Cardoso 2000 Ornitz and Itoh 2001 . Six FGFs, namely 1, 2, 7, 9, 10, and 18, are expressed in the lung e.g. Gonzalez et al. 1990 Fu et al. 1991 Colvin et al. 1999 . Four FGF receptors FGFRs are expressed in the lung Weinstein et al. 1998 . Particularly important in the development of complex, heterogeneous organs that form by budding and branching, e.g. lungs e.g. Cardoso 2001...

Arrangement of the Structural Components for Gas Exchange

Parabronchi

The arrangement of the IPRBArs and the IPRBAos relative to the orientation of the PR Figs. 67 and 68 determines how deoxygenated blood is delivered and exposed to air in the ET. The trajectories between the bulk air flow in the PRL and that of the venous blood from the IPRBArs are essentially perpendicular. Moving centripetally i.e. inwards , blood of uniform composition in O2 content is delivered practically at the same time to all parts of the ET of the PR. Blood thus equilibrates with...

Paleopulmo and Neopulmo

Hans Reiner Duncker 1971 was first person to point out that the structure of the avian lung was far from homogenous it consisted of two distinguishable anatomical and functional parts. Based on what he envisaged to be their chronological appearance during the evolution of the avian lung, he named the parts paleopulmo ancient old lung and neopulmo modern new lung . The paleopulmo occurs in the lungs of all birds while the neopulmo is totally lacking in some birds, especially the ancient...

Bronchial Airway System

Avian Lung

While the molecular and genetic controls of the development of the tracheal system of insects e.g. Sutherland et al. 1996 Jarecki et al. 1999 Sato and Kornberg 2002 and the BALu have now been well documented e.g. Cardoso 2000, 2001 Hislop 2002 Xiao et al. 2003 , little is known about the processes that occur in the avian respiratory system. In the domestic fowl, the embryonic lungs first become perceptible from day 3.5 about stage 26 Hamburger and Hamilton 1951 of embryogenesis e.g. Duncker...