ABSTRACT
For macroscopic and microscopic study of the omaso abomasal orifice the omasums and abomasums of ten fresh healthy cows between 12-18 months were used. Five of them for macroscopic observation of the orifice and the others for micrscopic study were used. For the later purpose tissues were cut from the cranial lateral and visceral sides and 5x5mm samples were fixed in 10% buffered formalin. Routine histologic method were used and 6 micro m paraffin sections were stained by haematoxylin eosin and studied under light microscope. The lengths of the mucosa, mucosal glands and the muscularis layer measured by graticule and the datas were analyzed statistically by the Anova test. By the study on the muscular layers at the different parts of the orifice and compare it with the other parts the abomasums it seems that the sphincteric function of the pilla omasi is the main role for closure of the orifice vela abomasica were helped to it to be completely closed