Question

the diagram shows the changes in thickness of the uterine lining during one menstrual cycle.

when would the levels of progesterone and oestrogen be highest?

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$$\begin{tabular}{|c|c|c|} \\hline & progesterone & oestrogen \\\\ \\hline a & between day 12 and 16 & between day 25 and 28 \\\\ b & between day 19 and 23 & on day 13 \\\\ c & on day 5 & between day 1 and 5 \\\\ d & on day 13 & on day 10 \\\\ \\hline \\end{tabular}$$

Explanation:

Analyze the uterine lining graph

The graph shows the thickness of the uterine lining over a 28-day menstrual cycle.

• Days 1 to 5: The lining thickness drops sharply, representing menstruation.
• Days 6 to 14: The lining gradually thickens, representing the proliferative phase.
• Days 15 to 28: The lining remains thick and highly vascularized, representing the secretory phase.

Determine peak oestrogen timing

Oestrogen is primarily secreted by the developing follicles in the ovary during the proliferative phase.

• Its level rises steadily to stimulate the repair and growth of the uterine lining.
• It reaches its peak concentration just before ovulation, which typically occurs around day 14.
• Looking at the options, "on day 13" (Option B) or "on day 10" (Option D) are during this pre-ovulatory window.

Determine peak progesterone timing

Progesterone is secreted by the corpus luteum, which forms from the ruptured follicle after ovulation (around day 14).

• Progesterone maintains the thick uterine lining for potential embryo implantation.
• Its levels rise during the luteal/secretory phase, peaking around the middle of this phase (typically between days 19 and 23).
• Looking at the options, "between day 19 and 23" (Option B) matches this peak luteal phase perfectly.

Correlate and select the correct option

Let's evaluate the combined hormone peaks:

• Progesterone peak: between day 19 and 23.
• Oestrogen peak: on day 13 (just before ovulation).
• This combination corresponds exactly to option B.

Answer:

• (A) progesterone: between day 12 and 16 | oestrogen: between day 25 and 28
• (B) progesterone: between day 19 and 23 | oestrogen: on day 13 (Correct answer)
• (C) progesterone: on day 5 | oestrogen: between day 1 and 5
• (D) progesterone: on day 13 | oestrogen: on day 10