Anatomy of the reproductive tract of the female muskox (Ovibos moschatus).

Reproductive tracts from 23 female muskoxen were collected from the Canadian high arctic during annual native muskox hunts. Twenty tracts were collected during the late breeding season and the last third of pregnancy or anoestrus, with 3 additional specimens taken just before the breeding season in August. The non-gravid muskox uterus was very similar to that of sheep and goats except for two features found in parous muskoxen. The first was endometrial pigmentation found only in the caruncles and associated with a dense collection of lipofuscin granules in the endometrial stroma. The second was a prominent 5 mm deep band of muscular tissue protruding from the antimesometrial border of the uterine horns throughout most of their length. The pregnant uterus and the fetal membranes of the muskox resembled homologous structures in domestic ruminants. However, there was no morphological evidence of a corpus luteum during late pregnancy, apart from a luteal scar in the ovary ipsilateral to the pregnant horn. Of the 4 females collected at the end of the breeding season, 2 lactating females were apparently not cyclic while 2 others had more than one CL, suggesting that they had undergone at least 2 cycles without conceiving or remaining pregnant.