CBSE Class 12-science Answered

The menstrual cycle is divided into four phases, namely:

1. Menstrual phase: Day 1, uterus lining which is prepared for implantation starts to shed which lasts 3 to 5 days.
2. Follicular phase: A matured egg follicle releases an egg from one of the ovaries. Also, uterus starts preparation for another pregnancy.
3. Ovulatory phase: Mid-cycle phase, this is the phase in which ovulation takes place i.e., day 13-17. End of follicular phase along with ovulation period defines the fertilization period.
4. Luteal phase: Post ovulation phase where the fate of corpus luteum is decided. If fertilization occurs, pregnancy starts. If fertilization doesn’t occur, it marks the onset of another cycle.