The proliferative phase of the uterine cycle ends when _____, secreted by the corpus luteum after ovulation, signals the endometrium that pregnancy could occur at any moment. The stratum functionalis is converted to a(n) _____ in response.

3000+ review questions on anatomy and physiology. 

Anatomy refers to the internal and external structures of the body and their physical relationships, whereas physiology refers to the study of the functions of those structures.