Structural failures of the blood–gas barrier and the epithelial–epithelial cell connections in the different vascular regions of the lung of the domestic fowl, Gallus gallus variant domesticus, at rest and during exercise

Abstract

SummaryStructural failure of blood–gas barrier (BGB) and epithelial–epithelial cell connections (EECCs) in different vascular regions of the exchange tissue of the lung was studied in rested and exercised chickens. The number of red blood cells (nRBCs) was counted and protein concentration (PC) measured after lavaging the respiratory system, and blood was sampled to determine the blood lactate levels (BLLs). The numbers of complete BGB breaks (nBGBBs) and those of the EECCs (nEECCBs) were counted in the different vascular territories of the lung. The nRBCs and the PCs increased with increasing exercise intensities but the rate of increase decreased at higher workloads. From rest to the fastest experimental treadmill speed of 2.95 m.sec−1, BLLs increased 4-fold. In all cases, the nEECCBs exceeded those of the BGB, showing that structurally the BGB is relatively weaker than the EECC. The increase in the number of breaks with increasing exercise can be attributed to increase in the pulmonary capillary blood pressure (PCBP) from faster heart rates and higher cardiac outputs, while the leveling out of the measurements made at higher workloads may have arisen from hemodynamic changes that initially ensued from exudation of blood plasma and then flow of blood into the air capillaries on failure of the BGB. The relative differences in the nBGBBs and the nEECCBs in the different vascular regions of the lung were ascribed to diameters of the branches and their points of origin and angles of bifurcation from the pulmonary artery. Presence of RBCs in the air capillaries of the lungs of rested chickens showed that failure of the BGB commonly occurs even in healthy and unstressed birds. Rapid repair and/or defense responses, which were observed, may explain how birds cope with mechanical injuries of the BGB.

Morphological and morphometric specializations of the lung of the Andean goose, Chloephaga melanoptera: A lifelong high-altitude resident

“…A τ ht of 0.118 μm was reported in the lung of a 3.84 kg body mass low altitude flying greylag goose ( Anser anser ) [33, 36, 37, 58]. For a bird that lives and flies in a cold and hypoxic environment where heart rate and cardiac output may need to be constantly high, the thicker BGB in the lung of the Andean goose may help avert structural failure of the BGB, a feature that has been reported to occur in the avian lungs [62, 63]. The particularly thick BGB of the lung of the Humboldt penguin [61] and the presence of plentiful connective tissue elements, especially of collagen in the BGB [64], was attributed to the capacity of the lung tolerating high hydrodynamic pressures during dives.…”

Pivotal debates and controversies on the structure and function of the avian respiratory system: setting the record straight

“…Studies of the strength of the air and blood capillaries of the avian lung have elicited a great deal of interest, controversy, and debate (Maina, ,, ; West et al, ,; West, Watson & Fu, ; Maina & Jimoh, ; Maina & Sikiru, ). The physical properties of these structural units have continued to evade complete appreciation long after they were first reported.…”

Evaluation of respiratory route as a viable portal of entry for Salmonella in poultry

“…[66][67][68][69][70][71][72][73] As a consequence, particles and particle-associated microorganisms are inhaled as unavoidable constituents of air flow. 74 The architecture of the avian respiratory tract is an important component in terms of susceptibility and resistance to infectious agents.…”

“…109 Based upon research on the microanatomy of avian lungs, it has been proposed that support of blood capillaries by surrounding air capillaries contributes to the strength of the capillary walls and thus allows a very thin and stable blood-gas barrier. [67][68][69] However, these properties appear to have conflicting roles, because thinness is essential for efficient flux of oxygen by passive diffusion, and strength is crucial for maintaining structural integrity. 72 Compared with mammals, arterial blood pressures in birds is much higher.…”