During which phase of the menstrual cycle is the endometrium described as having long, straight uterine glands with no secretions in the lumens?

The correct response indicates that during the follicular phase of the menstrual cycle, the endometrium is characterized by long, straight uterine glands that lack secretions.

In the follicular phase, which follows menstruation and precedes ovulation, the levels of estrogen begin to rise due to the developing ovarian follicles. This phase is marked by the proliferation of the endometrial lining, which is preparing for potential implantation of a fertilized egg. The glands that are formed during this time are straight and typically do not have secretions in their lumens yet because the secretory phase corresponding to high progesterone levels has not begun.

As the endometrium develops under the influence of estrogen, these changes are a prerequisite for the subsequent luteal phase when the endometrium becomes more glandular and secretory due to elevated progesterone from the corpus luteum. Understanding this hormonal regulation is essential for grasping the overall menstrual cycle dynamics and the morphological changes occurring within the endometrium at each phase.