THE DIFFERENTIATION OF THE SURFACE MUCOUS -CELL LINE IN THE ABOMASUM OF THE ADULT COW

The differentiation of the surface mucous-cell lineage during physiolo gical cell renewal was investigated using light and electron microscop y in the abomasal mucosa of adult cattle. The surface mucous cells con stitute a morphologically and functionally heterogeneous population, w hose members correspond to different developmental stages, arranged in a disto-proximal gradient from the depth of the pit towards the free luminal surface. The cell lineage comprises immature pre-pit cells nea r the proliferative isthmus, mature pit cells within the foveola, and older interfoveolar cells lining the free surface. Ultrastructurally, differentiation can be traced towards a predominantly mucus-producing cell type and finally towards a surface-protective cell variant, which degenerates in situ and is extruded into the lumen without affecting epithelial integrity.