The functional morphology of the large intestinal mucosa of the ox (Bos primigenius f. taurus), sheep (Ovis ammon f. aries) and goat (Capra aegagrus f. hircus)

The mucous membrane of the large intestine of the ox, sheep and goat was studied using light and electron microscopy. The surface epithelium possesses the well-known complement of organelles with a conspicuous number of mitochondria as a source of energy for absorptive activities. Occasionally, brush cells are found in the epithelium; the functional significance of this type of cell is still under discussion. In the present material, electron-lucid spheroids (diameter: 45 x 35 nm), which tend to fuse, appear in the supranuclearly located osmiophilic granules. The structure and appearance of the epithelium cells in the crypts of these species correspond to previous descriptions in other mammals. In the epithelial cells of the deep glandular region, dense accumulations of mainly rounded granules (diameter up to 400 nm) are found apically in the cytoplasm. Their functional significance is still under discussion. Acid phosphatase activity, as a marker enzyme for lysosomes, points to degenerative processes in connection with the physiological death of enterocytes. In contrast, the negative alkaline phosphatase reaction indicates that, according to our findings, the epithelial transport of substances in the large intestine of ruminants--in principle contrary to the situation in the small intestinal enterocytes--occurs without the aid of this enzyme. The demonstrated ATPase activity on the other hand, is related to a primary active ion transport linked with membrane exchange of non-electrolytes in connection with transepithelial events of absorption and secretion in the large intestine.