Changes

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Where oestrogens stimulate growth of follicles in the ovaries, oestrogens secreted from the ovary in the [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Follicular_Phase|follicular phase]] ([[Oestrous_Cycle_-_Anatomy_%26_Physiology#Pro-Oestrus|proestrous]] and [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Oestrus|oestrous]]) lead to hypertrophy of the epithelium and the endometrium. Secretory glands within the uterus enlarge and secretion is initiated leading to thickening of tissues.

Where oestrogens stimulate growth of follicles in the ovaries, oestrogens secreted from the ovary in the [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Follicular_Phase|follicular phase]] ([[Oestrous_Cycle_-_Anatomy_%26_Physiology#Pro-Oestrus|proestrous]] and [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Oestrus|oestrous]]) lead to hypertrophy of the epithelium and the endometrium. Secretory glands within the uterus enlarge and secretion is initiated leading to thickening of tissues. The blood vessels supplying the uterus and external genitalia dilate and blood flow to these areas increases significantly. Oedema occurs within the uterus and surrounding connective tissues. Oestrogen also causes increased uterine muscle tone. In the cervix oestrogens stimulate increased mucus secretion and the vaginal epithelium becomes keratinised.

Once near term, the concentration of progesterone decreases, altering the ratio between progesterone and oestrogen. This stimulates myometrial activity and prepares the uterus for parturition.