Gross anatomical and histomorphometric characteristics of the oviduct and uterus during the pubertal transition in sheep

Gross anatomical and histometric characteristics of oviducts and uteri were evaluated during the pubertal transition in ewe lambs. Lambs were hysterectomized prepubertally (PP; n = 10) or 26 +/- 2 h after onset of first (FE; n = 13) or third estrus (TE; n = 12), or estrus in mature pluriparous ewes (ME; n = 4). Gross characteristics included diameters, lengths, and weights of oviducts; diameters of uterine cornua; and weights of uteri. Histometric characteristics of ampullae, isthmi, and uterine cornua included epithelial cell volume, total luminal surface area, and total number of cells per ampulla or isthmus and area of the muscularis. Side of the reproductive tract did not affect (P > 0.10) any gross or histometric characteristic. Gross uterine characteristics increased (P < 0.05) dramatically between PP ewes and FE ewes, and then increased (P < 0.05) to a lesser degree between FE and TE ewes, and again (P < 0.05) between TE and ME ewes. Histological characteristics of uteri followed a similar developmental pattern: large changes (P < 0.05) between PP and FE ewes, slight increases between FE and TE ewes, and no change (P > 0.10) between TE and ME ewes. Oviductal weight and length showed little change (P > 0.10) at puberty or by third estrus, but they were greater (P < 0.05) in ME ewes than in the other groups. The diameters of ampullae increased (P < 0.05) at puberty, showed no change between FE and TE ewes, and were greatest (P < 0.05) in mature ewes. These changes seemed to be due to increases (P < 0.05) in mucosal cell height and muscularis area at puberty, and to muscularis area and submucosal thickness between TE and ME ewes. The surface area of the ampullae increased (P < 0.05) at puberty or by third estrus in a linear manner between PP, FE, TE, and ME ewes. The diameters of isthmi did not change (P > 0.10) at puberty but increased (P < 0.05) between FE and TE, and were greatest (P < 0.05) in ME ewes. The histological characteristics of isthmi followed the pattern observed in the ampullae. However, the surface area of the isthmi showed no change (P > 0.10) at puberty or by third estrus and was largest (P < 0.05) in ME ewes. Results of this study indicate that gross morphological characteristics of uteri and oviducts increase at puberty with either slight increases or changes after two estrous cycles. This relationship is also reflected by histological characteristics of these organs during the pubertal transition of sheep.