Table IX.

Changes in the Reproductive Organs of the Mouse during the Estrous Cycle^a

Stage.	Smearb	Uterus	Ovary and oviduct
Proestrus	Epithelial cells to epithelial-cornified cells or epithelial-cornified cells; leukocytes to epithelial cells	Hyperemia and distension increases. Active mitoses in epithelium, few leukocytes	Follicles enlarged and distended with considerable liquor folliculi. Few mitoses in germinal epithelium and in follicular cells
Estrus	Epithelial-cornified cells to cornified + cells	Distension and activity are maximal during estrus and then decrease. No leukocytes	Ovulation occurs, followed by distension of upper end of oviduct. Active mitoses in germinal epithelium and in follicular cells
Metestrus	Cornified + + cells, epithelial cells, leukocytes + +	Distension decreased. Leukocytes in epithelium. Walls collapsed. Epithelium degenerates. Mitoses rare	Follicles undergoing atresia. Growing corpora lutea. Eggs in oviduct. Few mitoses in germinal epithelium and in follicular cells
Diestrus	Epithelial cells, leukocytes, more or less mucus	Pale in appearance, walls collapsed. Epithelium healthy but contains many leukocytes. Some secretion by uterine glands	Follicles begin rapid growth toward end of period

^aAdapted from Bronson et al. (1996).

^b+ indicates many cells; + + indicates very many cells; – indicates transition from epithelial to cornified. The descriptions for smears are typical; there is considerable variation.