Scanning Electron Microscopic Study on the Microarchitecture of the Vascular System in the Pigeon Lung

Abstract

ABSTRACT. The resin casts of the respiratory and vascular systems in pigeon lung were examined using a scanning electron microscope. The primary bronchi branched to form many secondary bronchi that anastomosed with each other via the parabronchi. Numerous infundibula protruded from the parabronchi via the atria and ramified into the air capillaries. The pulmonary artery entered into the lung and branched into three vessels that coursed the interparabronchial parts. The intraparabronchial arterioles penetrated the gas-exchange tissue to form the anastomosing networks of blood capillaries. The observation of the double casts of the respiratory and vascular systems revealed three-dimensional complicated networks of air capillaries and blood capillaries. KEY WORDS: lung, pigeon, vascular system. J. Vet. Med. Sci. 67(10): 1071-1074, 2005 The respiratory organs of birds are structurally different from those of mammals. The avian lung is devoid of lobulation, alveoli, and tree-like branching of the air ducts that terminate in alveoli [8]. Hence, it can be assumed that the mechanics of breathing of birds are quite different from those of mammals [4].The respiratory system of the avian lung is composed of ramifying and anastomotic parabronchi (tertiary bronchi) [5]. These parabronchi that arise from the secondary bronchi occupy more than half of the avian lung volume in the form of dense bundles of interanastomosing tubes [8]. Some narrow columnar chambers (infundibula) protrude from the parabronchi via the dilated chamber or depression of parabronchial wall known as atria [15], and a number of air capillaries arise from the end of the infundibula [3,5,8,16].Based on the relationship between the direction of air flow and the direction of capillary blood flow within the alveolar walls, two systems for gas exchange in the avian lung have been theorized. These theories, namely, the counter (parallel) current system and the cross current system, are based on the anatomical and physical models as well as gas analysis [3,14,16].The anatomical relationship between the air capillaries and blood capillaries in the chicken lung is studied by the examination of an injected cast by using scanning electron microscope (SEM) [3,9,10] and transmission electron microscope [7]. However, the detailed morphological relationships between the terminal parts of these capillaries have not been verified. The cast of the blood capillary system in the pigeon lung is studied by the SEM in detail [15] but the respiratory system is not described. In this study, the fine structure of the double resin casts of both the respiratory tract and blood vessels in the pigeon lung was observed using SEM in order to elucidate the structural relationship between them at the level of the terminal parts of air capillaries and blood capillaries.All procedures were done in accordance with the "Guiding principles for the care and use of animals in the field of physiological sciences" of the Physiological Society of Japan. A total of 15 adult male pigeons were used in...

Evolution of Air Breathing: Oxygen Homeostasis and the Transitions from Water to Land and Sky

“…Avian lung structure has been reviewed extensively (184, 185, 186, 374, 375, 465, 475, 476, 481, 482, 485, 526, 566). On its dorsolateral aspect, the lung is deeply marked by the vertebrae and ribs (Fig.…”

“…30A-C). In the chicken, Pigeon and Black-Headed Gull, the infundibulae range from 25 to 40 μm in diameter (471, 501, 566, 815). Air capillaries comprise approximately 52% of total gas-exchange tissue volume (486) and anastomose profusely (Figs.…”

Three‐Dimensional Serial Section Computer Reconstruction of the Arrangement of the Structural Components of the Parabronchus of the Ostrich, Struthio Camelus Lung

“…Study of histological sections, as performed by Abdalla and King (1975), does not allow direct rendition to the three-dimensional (3D) arrangement: the 3D schemes that are developed pursuant to such studies depend largely on the intuition and judgment of the investigator and may be subject to personal bias. Regarding the casting method that was used by West et al (1977), Maina (1982Maina ( , 1988, and Nasu (2005), the accuracy depends on the suitability and the nature of the material used for injection in relation to the size of the structures that are cast. Artifacts may arise from underfilling, overfilling, or in extreme cases extravasation of the material, after failure of the wall of the conduit (Murakami, 1971;Clark et al, 1979;Ohtani, 1980;Lametschwandtner et al, 1984).…”

Recent Advances into Understanding Some Aspects of the Structure and Function of Mammalian and Avian Lungs

“…West et al (1977, p. 557) remarked that the parenehyma showed "a dense, apparently random, three-dimensional 'sponge' of blood eapillaries and air eapillaries"; Duneker (1989) observed that the ACs and BCs form "a sinusoidal three-dimensional network"; Bellairs and Osmond (1998) stated that the parenehyma "resembles a sponge in strueture"; and Makanya et al (2007Makanya et al ( , p. 1142 reported that the parenehyma eomprises "a dexteriously erafted blood capillary network that interfaces with the equally eomplex air eapillary labyrinth." Examination of two-dimensional histologieal seetions by light mieroseopy (LM) and easting have mainly been used in attempts to explieate the morphologies and spatial organization of the ACs and the BCs (e.g., Abdalla and King 1975;West et al 1977;Maina , 1988Nasu 2005). These methods have eertain limitations.…”