Because the endometrium undergoes cyclic changes as a result of ovarian hormones, it’s crucial to understand the interrelationships between the pituitary, ovary, and uterus at various times of the menstrual cycle. Following menstruation, the proliferative period is marked by endometrial repair and the development of relatively straight, tubular uterine glands. At this stage, the endometrial stroma (area between glands) has a thick, cellular look. During the proliferative period, coiled endometrial arterioles are not visible.