Muscular architecture in the omasal laminae of cattle and sheep.

The muscular architecture of the bovine omasal laminae was examined. The omasal laminae had three thin smooth muscle layers which consisted of an intermediate layer and two lateral layers. The muscle bundles of the intermediate layers ran radially in the laminae and those of the two lateral layers ran parallel to the free border of the laminae. At the free border, three types of the muscular architecture were observed. In a histological study, the muscle bundles of the intermediate layer penetrated into the connective tissue around and smooth muscle fasciculi of the inner layer of the tunica muscularis of the omasal wall and attached to the bundles of both the inner layer and of the outer layer of the tunica muscularis. These results indicate that a re-evaluation of the muscular architecture in the omasal laminae is required to facilitate better understanding of the omasal morphology and physiology.