Ultrastructural differences between the two major components of chicken ceca.

The central parts of basis and corpus ceci from White Plymouth Rock hens on different salt regimen were investigated by light, scanning electron, and transmission electron microscopy. The mucosal surface varies from long broad, flat villi in basis to blunt rugae in corpus ceci. In the epithelium of basis ceci there are many goblet cells, whereas in corpus ceci they are few in number and predominantly located in the crypts and sides of rugae. The microvilli of basis ceci are longer than those of corpus ceci. The epithelium from corpus ceci contains apically located cytoplasmic inclusions of microtubular-like aggregations. The size and amount of these inclusions decrease towards the crypt openings, and none were observed in crypt epithelium. The mitochondria in the epithelium from basis ceci are seen close to the apical plasma membrane, but in corpus ceci they first appear deeper in the cytoplasm below the apical vesicles, microtubular-like aggregations, and lysosomes. The size and content of the apical vesicles varies between the two compartments, as do deposits of lipoglycoproteins in the intercellular space and vesicles of the lateral plasma membrane. Several differences were thus revealed between the epithelia from basis and corpus ceci, giving morphological evidence for different functions between the two compartments. There were no effects of the two salt diets on the development of microvilli, whereas some cytological differences, such as the degree of microtubular-like aggregations, were seen in corpus ceci.