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Multiple Choice
Which event marks the transition from the proliferative phase to the secretory phase in the menstrual cycle?
A
Menstruation
B
Implantation
C
Fertilization
D
Ovulation
Verified step by step guidance
1
Understand the menstrual cycle phases: The menstrual cycle is divided into four main phases: menstruation, the proliferative phase, ovulation, and the secretory phase. Each phase is characterized by specific hormonal changes and physiological events.
Focus on the proliferative phase: During the proliferative phase, the endometrium (lining of the uterus) thickens under the influence of estrogen, preparing for potential implantation of a fertilized egg.
Identify the transition event: The transition from the proliferative phase to the secretory phase is marked by ovulation, which is the release of an egg from the ovary. This event is triggered by a surge in luteinizing hormone (LH).
Understand the secretory phase: After ovulation, the secretory phase begins. During this phase, the corpus luteum forms and secretes progesterone, which further prepares the endometrium for implantation of a fertilized egg.
Clarify why ovulation is the correct answer: Ovulation is the key event that separates the proliferative phase from the secretory phase. Menstruation occurs before the proliferative phase, fertilization may happen after ovulation, and implantation occurs during the secretory phase if fertilization has taken place.