Vagina

The vagina is the portion of the reproductive tract that lies within the pelvis between the uterus cranially and the vulva caudally (Figs. 26-1 and 26-5). The vagina is the birth canal for delivery of the fetus at parturition and a sheath (vagina is Latin for sheath) for the penis of the male during copulation (the act of breed­ing, or service, as it is commonly called in animal husbandry).

The mucous membrane of the vagina is glandless stratified squamous epithelium except in the cow, in which there are some mucous cells in the cranial part of the vagina adjacent to the cervix. The submucosa is loose, and the muscular layers consist of an inner circular and an outer longitudinal layer of smooth muscle. A serosa (the peritoneum) invests only on the cranial part of the vagina, where it lies within the pelvic cavity. The caudal portion of the vagina, passing through the pelvis, is covered by pelvic fascia (connective tissue).