Anatomy and Physiology II Practice Test 2026 - Free Anatomy Practice Questions and Study Guide

During the secretory phase of the menstrual cycle, progesterone levels peak due to the activity of the corpus luteum, which forms after ovulation. The primary role of progesterone is to prepare the endometrium for potential implantation of a fertilized egg. It causes the endometrial lining to thicken and become more vascularized and glandular, providing a suitable environment for embryo development.

This phase follows ovulation and is primarily influenced by luteinizing hormone (LH) and the secretion of progesterone from the corpus luteum. While estrogen levels also rise in a preceding phase, and there can be a subsequent increase in estrogen during the secretory phase, it is progesterone that reaches its highest concentration during this time. Elevated progesterone signals the body to maintain the endometrial lining, and if pregnancy does not occur, progesterone levels will decline, leading to the onset of menstruation.

The other hormone options, while important in their own right, do not peak during this phase. Follicle-stimulating hormone (FSH) primarily acts in the follicular phase to stimulate ovarian follicle development. Luteinizing hormone (LH) peaks just before ovulation, facilitating the release of the egg. Estrogen, although