Final answer:
The correct statement about changes during the menses phase of the menstrual cycle is D) the old functional layer is sloughed off, as this is the time when the endometrial lining that has built up over the cycle is shed.
Step-by-step explanation:
The student questions pertain to changes in hormonal levels and uterine dynamics during the menstruation phase of the menstrual cycle. In this phase, progesterone levels are low because the corpus luteum degenerates due to the absence of pregnancy and the resultant drop in progesterone triggers the shedding off of the endometrial lining. This is known as menses. Hence, during menses:
- Progesterone levels are not high; they are actually low after the corpus luteum degenerates.
- A new uterine lining is not immediately formed; this occurs later in the menstrual cycle.
- Secretory glands and blood vessels in the endometrium have been developed and are now being shed off, not developing.
- The old functional layer is sloughed off; this is correct and corresponds to the shedding of the stratum functionalis of the endometrium.
- The corpus luteum is not most active; it degenerates during menses due to the absence of a fertilized egg implantation.
Therefore, the correct statement is D) the old functional layer is sloughed off.