Gas-Exchange Efficiency of Fish Gills and Bird Lungs

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Abstract

A simplified general functional schema of gas-exchange organs (Piiper 1982; Piiper and Scheid 1975, 1982a) is shown in Fig. 13.1. Medium, with flow date V, and blood, with flow rate Q, come into gas-exchange contact, leading to O2 uptake by blood and CO2 output from blood. The better the gas-transfer conditions, the closer come PO 2 and PCO 2 in medium and blood. a complete “overlap” (arterial equal inspired, venous equal expired partial pressure), as shown in case 4 of Fig. 13.1, can only be reached with an ideal countercurrent system, i.e., lacking diffusion limitation, and with perfect matching of blood and gas conductances (Piiper and Scheid 1982b, 1984).