Fine structure of developing gastric parietal cells in the bovine abomasum.

Developmental changes in the fine structure of gastric parietal cells were studied in bovine fetuses and neonates. Definitive parietal cells first appeared as non-granular light cells at five months of fetal age (in a 48 cm long fetus). At this age they had a microvillous apical surface and cytoplasmic vesicles which accumulated at the apex. Intracellular canaliculi appeared with an increase in mitochondria at six to seven months of fetal age. Fully differentiated parietal cells were present from the eighth month of gestation. At birth they were similar in appearance to those of the adult abomasum.