Physical Changes During The Female Dog's Complete Estrus Cycle

As we have already seen before, usually the external sign that a dog is developing the different estrus phases coincides, first of all, with the increase in size of the vulva, then with the vaginal discharge and finally with the reaction of the vulva to touch. Concretely, the swelling of the vulva usually takes place during preestrus and estrus, when the levels of estrogen vary considerably, although it isn't clear why on some occasions this swelling is higher or lower. Maybe reaching can be in the amount of estrogen secreted in each cycle.

The moment of greater vulvar turgidity coincides with the days immediately before estrus, when the lips are very inflamed and pink; after that, during estrus itself, the turgidity seems to go down, in order to make it easy for the male dog's penis to penetrate and, finally, when the estrus stage is over and the dog enters the stage of diestrus, the vulva practically goes back to its normal state and science. I say practically because you will observe that the size of the vulva after the first heat period is a little bit bigger than before. In fact, in only some females which have gone through the process of ovarian hysterectomy or the excision of one or all of the internal reproductive organs, double the returns to its prepubertal size, as long as she hasn't given birth.