The function of the uterus: storage, screening and transportation of sperm, which helps the sperm to acquire energy and come into estrus. After mating, the opened cervix is ​​conducive to the entry of sperm and has the ability to prevent dead sperm and abnormal sperm from entering the uterus, which can prevent excessive Sperm reaches the site of fertilization. A large amount of sperm is stored in the complex cervical crypts. Sperm entering the uterus are transported to the fallopian tube by the contraction of uterine muscles. Under the action of endometrial secretions, the sperm can be capacitated.

The secretion of endometrium during conception attachment, pregnancy and delivery can not only capacitate sperm, but also provide nutrients for early embryonic growth and development. When the blastocyst is implanted, the endometrium forms the maternal placenta and combines with the fetal placenta to create a good environment for the growth and development of the fetus. During pregnancy, the cervical mucus is highly viscous and forms a plug, sealing the cervix and acting as a barrier to prevent uterine infection. Before delivery, the cervical embolus liquefies, the cervix dilates, and the fetus and fetal membranes are expelled with the contraction of the uterus.

The vagina is entirely located in the pelvic cavity, between the rectum and the bladder. There is a small depression behind the cervix at the front end, and the vaginal valve (a horizontal mucosal fold) at the back end serves as the boundary between the vagina and the urogenital vestibule. The dog's vagina is long, and the front end is connected to the cervix. It is a lumen composed of an expansile and strong muscular membrane. The front part of the vagina is the vaginal dome, which is thin and has no obvious dome. The cervix and vagina protrude 0.5lcm from the vaginal cavity in a conical shape from the front and top, and its diameter is (X 8lcm.

The posterior end of the vagina is connected to the urogenital vestibule. 1. Uterine body 2. Cervix 3. Cervical external opening 4. Vagina regulates the function of the corpus luteum of the ovary, causing the estrous uterus to regulate the function of the corpus luteum through the local uterine-ovarian vein-ovarian artery circulation. and estrous cycle. The non-pregnant uterine horn secretes prostaglandins during a certain period of the estrous cycle, which dissolves and degrades the ovarian corpus luteum, induces the secretion of gonadotropin, causes a new round of follicle development and leads to estrus.

The less obvious vaginal valve serves as a dividing line. Since the cervix and vagina protrude from front to back, the dorsal wall of the vagina is short and the ventral wall is long. The length of the vagina of various dogs is different. The length of the vagina of an adult medium-sized dog is generally 915cm, and the length of the vagina of an adult German Shepherd is 18cm. The vaginal wall has several longitudinal folds. The vaginal cavity is soft, dilated, and contractible. The diameter of the vaginal cavity is approximately 1.52.5cm.

Tissue Structure The vaginal wall can be divided into three layers: mucosa, muscularis and adventitia. The mucosal layer is divided into epithelial layer and lamina propria. The epithelium is stratified squamous squamous epithelium. Epithelial cells change regularly with the sexual cycle. The basal cells of the lamina propria are cuboidal with little cytoplasm and oval nuclei, densely arranged vertically. on the membrane propria. The submucosa has a network of blood vessels but no glands. The muscle layer is smooth muscle, with a thin layer of longitudinal muscle on the inside, a thick circular muscle in the middle layer, and a thin layer of longitudinal muscle on the outside.