What tissue and hormonal phase occurs during the last 14 days of a normal 28-day menstrual cycle?

During the last 14 days of a normal 28-day menstrual cycle, the secretory luteal phase is characterized by specific hormonal influences and tissue changes. Following ovulation, the corpus luteum forms, which secretes both estrogen and progesterone.

Progesterone plays a vital role in preparing the endometrium for potential implantation of a fertilized egg. Under the influence of these hormones, particularly progesterone, the endometrial lining transforms to a secretory state, which includes increased vascularization and glandular development. This transformation is crucial for supporting early pregnancy should fertilization occur.

The secretory phase is defined not only by the presence of progesterone but also by estrogen, which continues to support the endometrial lining, albeit at lower levels compared to progesterone. The transition from the proliferative phase, where estrogen predominantly drives growth of the endometrial lining, to the secretory phase, which emphasizes progesterone's effects, marks this critical part of the menstrual cycle.

The other choices either incorrectly attribute the phase to the proliferative phase, which occurs in the first half of the cycle, or suggest an imbalance in the hormonal influence during the luteal phase.