Ultrastructural observations on the caecum of the rabbit.

The caecal mucosa of the rabbit has been studied using transmission electron microscopy and its fine structure is considered in the light of its known secretory and absorptive capacities. The luminal surface consists of columnar absorptive epithelium while the crypts are lined with glandular epithelium comprising undifferentiated cells, goblet cells containing dark and light mucigenous granules, and intra-epithelial cells. Endocrine cells occur more commonly in the cryptal epithelium and two cell types have been recognised which correspond to EC and L cells respectively. The lamina propria includes lymphocytes, plasma cells, mast cell and smooth muscle cells. There is little ultrastructural variation within mucosal cells along the length of the caecum.