Final answer:
The luteal phase is the post-ovulatory phase of the ovarian cycle, marked by the transformation of the ovulated follicle into the progesterone-secreting corpus luteum, which prepares the uterus for potential pregnancy and inhibits further ovulation.
Step-by-step explanation:
The luteal phase is the third and final phase of the ovarian cycle, occurring after ovulation and before the start of menstruation. It typically lasts around 14 days in a 28-day menstrual cycle, running from about day 15 to 28. During this phase, the follicle that released the egg transforms into a corpus luteum, a structure that secretes significant amounts of progesterone, as well as estrogen. The progesterone is crucial for maintaining the endometrium, preparing the uterus for potential pregnancy, and inhibiting the release of further follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which prevents any further eggs from developing during this cycle. If the egg is not fertilized, the corpus luteum will degrade into the corpus albicans, leading to a decrease in progesterone levels, which triggers the start of the menses phase and the shedding of the uterine lining.