Fig. 2.

The changes of biology during different estrus cycle. Estrogen and progesterone are secreted via the ovary or uterus and undergo changes during the estrus cycle. In addition, the basal body temperature also changes, while the thickness of the endometrium has corresponding transformations. After menstruation, the new estrus cycle starts to develop. During the follicular period, the level of the basal body temperature and estrogen gradually rise. The thickness of the endometrium also increases. The levels of basal body temperature and estrogen maintain certain concentrations until the ovulation period. Thus, progesterone starts to increase. With the appearance of the luteal phase, all changes are restored until the end of menstruation