THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -If a fertilised egg implants in the lining of the uterus, the corpus luteum continues to produce progesterone, which maintains the thickened lining of the uterus. If pregnancy does not occur, the corpus luteum dies, progesterone levels drop, the uterus lining sheds and the period begins again.

Detailed explanation-2: -If fertilization does not occur, the endometrium, coupled with blood and mucus from the vagina and cervix (the lower, narrow part of the uterus located between the bladder and the rectum) make up the menstrual flow (also called menses) that leaves the body through the vagina.

Detailed explanation-3: -The ovulation phase During ovulation, the mature egg travels from the ovary, down the fallopian tube, and into the uterus.

Detailed explanation-4: -Luteal phase (day 15-28) If a sperm cell does not impregnate the egg cell within that time, the egg cell disintegrates. The hormone that causes the uterus to retain its endometrium gets used up by the end of the menstrual cycle.