What term is used for the phase of the menstrual cycle during which the uterine lining thickens?

The phase of the menstrual cycle during which the uterine lining thickens is known as the luteal phase. This phase follows ovulation, which occurs after the follicular phase, and is characterized by the secretion of hormones, particularly progesterone, from the corpus luteum formed from the ruptured follicle. Progesterone plays a crucial role in preparing the endometrium for potential implantation of a fertilized egg, leading to the thickening of the uterine lining. If implantation does not occur, the corpus luteum degenerates, hormone levels drop, and the menstrual phase begins. The luteal phase typically lasts around 14 days, illustrating the importance of hormonal regulation during this stage of the menstrual cycle.

In contrast to the luteal phase, the follicular phase is focused on the maturation of ovarian follicles and the buildup of the uterine lining, but it is not the period when the lining is actively thickening due to hormonal influences like during the luteal phase. The menstrual phase involves the shedding of the uterine lining, and the ovulatory phase marks the release of the egg, neither of which directly correlates to the thickening of the lining.