The equine cervix

Abstract

The cervix of the mare has not been studied much, although its important role in reproduction has been recognized. The cervix is one of the sphincters of the female reproductive tract. Prevention of uterine contamination from the caudal tract is vital for the uterine health and for a successful pregnancy; the cervix has to be tightly closed to seal the uterus. On the other hand, during estrus the cervix has to soften and dilate. The open cervix allows the entrance of sperm into the uterus, but also facilitates the elimination of excessive sperm and inflammatory by-products after insemination. Failure to open adequately is a common cause for insufficient uterine drainage in maiden mares. During parturition, the cervix has to ripen and dilate enormously to allow the delivery of the foal. Involution of the cervix proceeds rapidly, and after the foal heat ovulation the cervix should close in a normal fashion. Cervical lacerations and adhesions are pathological consequences of foaling. The equine cervix has a simple structure and can therefore be manually dilated any time. The tunica mucosa is branched to primary, secondary and tertiary folds. The simple columnar epithelium consists of two types of cells: non-ciliated goblet-like cells which produce mucin and kinociliated cells. The examination methods are transrectal palpation, transrectal ultrasonography, transvaginal palpation and vaginoscopy. Based on the examination findings the cervix has been divided into four categories indicating different degrees of steroid hormone influence and subsequently the stage of the estrous cycle. Developmental abnormalities of the mare's cervix are rare, but some have been reported. Cervical lacerations and adhesions result from parturition. Failure of cervical dilation may be congenital or required. Fibrosis is most commonly encountered in old maiden mares. Failure to open results in accumulation of intrauterine fluid because of deficient drainage and leads subsequently to uterine inflammation and infection and lowered fertility. This paper is a review of the literature published about the equine cervix including anatomy, histology, physiology, examination, pathology and cervical drainage.