In this study, uterus along with ovaries collected from 40 Malcoee (A sheep reared in west Azerbaijan of Iran) ewes, considering their ages, and health condition. Microscopic studies revealed that, mast cell and plasma cell distribution around the deeper portions of the uterine glands, comparatively were aboundant and their population were greater in spring and summer season compared to atumn and winter, whereas distribution of fibroblast in superficial portions of the endometrium as well as caruncles was greater. In aturnn & winter, compared to spring and summer, there was significant incraese in fibroblast count (P<0.05). The result of this experiment shared that, in first two season of year, because of reduced frequencies of oestrous cycle, and respect to that, reduced hormonal levels (specialy progesteron), Plasma and mast cell populations increased and elaborate the defense mechanism of uterus, whereas in to other season of year i.e., autumn & winter, because of healt sexual activity of sheep, and increased hormonal level, especialy estrogen, increased the defens mechanism. Increasement of estrogen level in this season, with reference to this mitogenic action on stromal cells, may be the reason for significant increased fibroblast populatin (P.<0.05) Statistical analysis showed that fore mentioned changes occur uniformly throughout endometrium of the sheep understudy, in different stages of oestrous cycle, and there were no significant difference, between parameters in different stages of oestrous cycle.
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