Final answer:
Estrogen is the ovarian hormone that reaches its highest concentration during the proliferative phase, promoting uterine lining growth and mucus production at the cervix to facilitate fertilization.
Step-by-step explanation:
The ovarian hormone that reaches its highest concentration during the proliferative phase is estrogen. This phase is the second phase of the uterine cycle, where estrogen, secreted by the cells of the maturing ovarian follicle, prompts the lining of the uterus to grow.
The role of estrogen is pivotal as it not only stimulates the growth of the uterine lining but also increases the amount of thinner mucus at the cervix, enhancing the possibility of sperm passage and potential fertilization.
After ovulation, which marks the end of the proliferative phase, there's an increase in another hormone, progesterone, as the corpus luteum forms from the granulosa cells of the collapsed follicle. Progesterone then begins the secretory phase, preparing the endometrium for a possible implantation.