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Ovary of a pigeon (HE): overview
Generally in birds, only the left ovary is present. Exceptions are the Order Apterygiformes (the kiwi) and some species or individuals of the Order Falconiformes, who also have or can have a right ovary.
During hatching season, follicles develop en masse in the cortex (zona parenchymatosa). They grow enormously by accumulation of yolk in the cytoplasm of the oocyte. The mature follicles move to the periphery but stay connected with the ovary by a follicular stalk or pedicle (pedunculus folliculi). The medulla is strongly reduced and is mainly limited to the central part of the follicular stalks (zona vasculosa). The transition between cortical and medullary connective tissue is vague. Blood vessels and nerves from the mesovarium enter the ovary at the hilus.
The left adrenal gland lies mostly embedded at the hilus.