Surface aspects of the rabbit gallbladder mucosa and their functional implications

The morphology of the internal surface of the distended (filled) gallbladder and the sequence of its alterations during emptying were studied by scanning electron microscopy and light microscopy in the rabbit. Emptying was obtained by injecting a single dose intramuscularly or subcutaneously of caerulein varying from 0.01 μg/kg to 1 μg/kg. With scanning electron microscopy the mucosa in the distended state displays folds of differing heights, which frequently anastomose with each other, forming a network of bays varying in size. Many of the folds leave the network disappearing as a crescent-like ridge into the bays. Light microscopy shows a network of vessels particularly thick in the folds. During emptying, the mucosa shows both a progressive reduction in the size of the bays and a gradual elevation of the folds which become very twisted and are in close apposition to each other, producing a regularly waved surface. The vessels in the crescent-shaped folds connect the superficial with the deeper vasculature and act as fixed points determining the recurrence of a regular pattern of the mucosa each time the organ becomes empty. Therefore, emptying of the rabbit gallbladder results in a regular and repeatable modification of the mucosal pattern observed in the control animals.