Fine structure of the porcine myometrium during the oestrous cycle

The ultrastructure of the porcine myometrium was studied at well-defined stages of the oestrous cycle by transmission electron microscopy. The fine structure of the myometrium in the pig was found to be similar to that observed in other genital organs and species and did not show obvious variations through the oestrous cycle. The cell-to-cell contacts between smooth-muscle cells most consistently found were intermediate junctions and simple appositions, whereas interdigitations of muscle cell processes were more sparse. Gap junctions were few and small. Nerve terminals possessing presynaptic vesicles typical of the adrenergic and cholinergic type were found, though sparsely, both within and close to muscle bundles.