| Stage | Smeara | Histology of the vaginal epithelium |
Uterus | Ovary and Oviduct | ||||
| Proestrus | E to EC or ECL to EC |
Many cell layers (10 to 13). Outer 4 or 5 nucleated, stain lightly with eosin. Under these, granulosa layer showing increasing cornification. Active mitoses. Few leukocytes. |
Increasing hyperemia and distension. Active mitoses in epithelium, few leukocytes. |
Follicles large and distended with considerable liquor folliculi. Few mitoses in germinal epithelium and in follicular cells. |
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| Estrus | EC to C+ | Superficial nucleated layer lost. Cornified layer now superficial. About 12 layers of nucleated cells under this. Mitosis decreasing. Leukocytes absent. |
Distension and mitotic activity reach maximum during estrus, and then decrease. No leukocytes. |
Ovulation occurs followed by distension of the upper end of oviduct. Active mitoses in germinal epithelium and in follicular cells. |
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| Metestrus-1 | C++ | Cornified layer delaminated. Leukocytes begin to appear under epithelium. |
Distension decreased. Leukocytes begin to penetrate epithelium. |
Early corpora lutea present. Eggs in oviduct. Many follicles undergoing atresia. |
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| Metestrus-2 | C++ EL++ | 4 to 7 layers of epithelial cells, with very many leukocytes in outer layers. |
Walls collapsed. Epithelium shows degeneration. Mitoses rare. Leukocytes numerous. |
Growing corpora lutea. Eggs in oviduct. Few mitoses in germinal epithelium and in follicular cells. |
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| Diestrus | EL, more or less mucus | 4 to 7 layers of epithelial cells, with very many leukocytes in outer layers. Growth commenses towards end of diestrus. |
Anemic, walls collapsed. Epithelium healthy but contains many leukocytes. Some secretion by uterine glands. |
Follicles begin rapid growth toward end of period. |
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| a E = epithelial cells, C = cornified cells, L = leukocytes, + indicates many cells, ++ indicates very many cells. The smears given are typical; there is considerable variation. | ||||||||