Question

(a) Explain menstrual cycle in human females.
(b) How can the scientific understanding of the menstrual cycle of human females help as a contraceptive measure?

Answer 1

(a) The cyclic changes that take place in a rhythmic fashion in the ovaries and uterus of female reproductive tract during the reproductive period of a women's life is called menstrual cycle or female reproductive cycle. It occurs only in female primates. It is of 28 days (may vary from 22-40 days). It is controlled by 4 hormones: Follicle Stimulating Hormone (FSH), Luteinising Hormone (LH), Estrogen and Progesterone. The menstrual cycle is divided into four phases: 1) Menstrual phase or destructive phase, 2) Follicular phase or Proliferative phase, 3) Ovulatory phase, 4) Secretory phase or Luteal phase

1) Menstrual Phase (1st to 4th day of menstrual cycle): When the ovum is not fertilized, the pituitary gland stops producing LH. The level of LH decreases. Corpus luteum degenerates and converts into a white body called corpus albicans. Progesterone level decreases and the endometrium breaks and fall. Also, the endometrial epithelium, blood vessels and uterine glands break and fall off. The endometrial debris, blood, mucus and unfertilized ovum flow through the vagina. This is called menstrual bleeding, during which 35-45 ml of blood is lost. Endometrium becomes 1mm thin.

2) Proliferative Phase (5th to 13th day of menstrual cycle): Pituitary gland produces FSH, leading to high FSH. High FSH level stimulates primordial follicle to mature into Graafian follicle. FSH stimulates the theca interna of Graafian follicle to produce estrogen. Hence, estrogen level increases. Estrogen causes endometrial repair, growth and proliferation. Endometrial epithelium, blood vessels and uterine glands regrow. Endometrium becomes 3-5 mm thick.

3) Ovulatory phase (14th day of menstrual cycle): The level of estrogen becomes maximum on 12th day of the cycle which stimulates the pituitary gland to produce LH. Hence, the LH level starts rising and suddenly there is a sharp increase in the levels of LH. This is called LH surge. LH surge leads to ovulation. Graafian follicle ruptures and ovum is released into pelvic cavity or abdominal cavity. The ovum enters the fallopian tube through the ostium assisted by fimbriae. The ovum must be fertilized within 24 to 48 hours after ovulation. Only during this time it is viable for fertilization. If fertilization takes place then the fertilized egg passes through the fallopian tube and reaches the uterus on third day after ovulation.

4) Secretory phase (15th to 28th day of menstrual cycle): Pituitary gland continues to produce LH, leading to high LH level. High LH level converts ruptured and empty Graafian follicle into a yellow body called corpus luteum. Corpus luteum produces progesterone. So, progesterone level increases and holds the endometrium. Uterine glands enlarge, get coiled and produce uterine fluid rich in glycogen which provides nutrition to the developing embryo. Endometrium becomes 5-6 mm thick.

(b) The scientific understanding of the menstrual cycle of human females helps as a contraceptive measure in the following ways:

1) Prevents pregnancy by monitoring the fertile periods during the menstrual cycle

2) Allows women to avoid sexual intercourse or use alternative contraceptive methods during the fertile stages of their menstrual cycle

3) Increased self-awareness and knowledge of their fertility

4) Increased reliance on their own resources rather than a family planning program or other sources of contraception

5) Increased independence from costly or distant medical services

6) Freedom from artificial substances and the side effects or potential medical risks of other methods