Ovarian cyclicity induces considerable changes in morphology, physiology and function of the reproductive organs in animals. This thesis aimed to study reproductive physiology of the female domestic cat, focusing on the cervix, uterus and uterine tube during different stages of the oestrous cycle, after mating and under pathological conditions. Transcervical catheterisation was performed using a specially designed catheter. Patency of the cervix and uterine motility were studied with the aids of fluoroscopy and scintigraphy by depositing contrast fluids and radiopharmaceutical medium in the cranial vagina. The relationship between cervical patency and oestrous behaviour, cornification of the vaginal cells and serum concentrations of oestradiol-17β were evaluated. Hysterography, a positive contrast study, was performed to illustrate the uterine appearance during the oestrous cycle in relation to histological characteristics of the endometrium. Immunohistochemistry using proliferating nuclear antigen (PCNA) was introduced to identify mitotic activity of the endometrial cells. Patency of the cervix to spermatozoa as well as sperm distribution after natural mating was evaluated by flushing the vagina, the uterus and the uterine tube. For the study of sperm distribution in the female reproductive tract, two methods, flushing and tissue sectioning were evaluated and compared. Using a specially designed catheter it was possible to catheterise the cervix during interoestrus, oestrus, metoestrus and postpartum and to introduce contrast fluids into the uterus to study uterine appearance using hysterography also when the cervix was closed. The period when the cervix was patent was found to vary among individuals: the cervix was open either only during late-oestrus; during midoestrus and late-oestrus; or throughout the entire behavioural oestrus. Patency of the cervix was found to usually coincide with the maximum degree of vaginal cornification and thus, presumably is regulated at least in part by the serum concentration of oestradiol-17β. Hysterograms revealed differences in uterine luminal shape that corresponded to the histological characteristics of the endometrium in cats at various stages of the oestrous cycle, cats given medroxyprogesterone acetate (MPA) and cats with uterine pathology. Straight- and wavy-shaped uterine lumens were characteristic of the uterine horns in the inactive and follicular stages of the oestrous cycle, respectively. Coil-shaped uterine lumen appeared to be a progestagenic effect seen in the luteal, the MPA-treated and the pathological groups. A coiled uterine cavity was suggestive of endometrial hyperplasia, whereas irregular filling defects were indicative of generalised cystic changes in the endometrium. The expression of PCNA in luminal and glandular epithelial cells was observed although the mitotic activity was not related to neither stages of oestrous cycle nor uterine pathological conditions. The results from the sperm distribution study demonstrated that the cervix and the uterotubal junction (UTJ) were sperm barriers in the cat. The endometrial crypts and the UTJ functioned as sperm reservoirs before ovulation, whereas the isthmus was a sperm reservoir around the time of ovulation. The observations determined the dynamics of the cervix, the uterus and the uterine tube in the cat in relation to ovarian activity. This thesis is the first to provide nomenclatures for describing uterine appearance in hysterograms according to the shape of the uterine horns, luminal cavity and the characteristics of the intraluminal lining, to demonstrate the PCNA expression as well as to determine the distribution of spermatozoa in the female reproductive tract of the cat after natural mating
