Intralamellar blood flow patterns in fish gills.

The dimensions of the lamellar vascular sheet in ling cod gills were examined over a range of transmural pressures (delta Plam). The mean vascular sheet thickness (h) increased linearly with delta Plam over the range 30-60 cmH2O, where h = 8.36 + 0.07 delta Plam. The vascular space-to-tissue ratio, however, was unchanged over the pressure range examined. Thus sheet flow equations, formerly derived for the interalveolar wall of the mammalian lungs, can be used to describe blood flow through the lamellae. Predictions were made on the distribution of blood flow within the lamella. When delta Plam and flow are raised, blood flow is redistributed away from the base of the lamella, since regional variations exist in the thickness and the vascular compliance of the lamellar sheet. Variations in the pattern of intralamellar blood flow are likely to affect gas transfer in the gills.