Human Reproduction and Contraception

Menstruation starts at puberty which is known as menarche. It is the shredding of endometrial lining, ovum and some blood vessels. It ends at the age of 45 to 50 which is known as menopause. It is a cyclic process which happens every month. It includes the menstrual phase, the follicular phase, the ovulatory phase, and the luteal phase. Ovulatory phase happens because of a sudden release of LH hormone.

After ovulation, the pituitary hormones FSH and LH cause the remaining parts of the dominant follicle to transform into the corpus luteum, which produces progesterone. The increased progesterone in the adrenals starts to induce the production of estrogen. The hormones produced by the corpus luteum also suppress production of the FSH and LH that the corpus luteum needs to maintain itself. Consequently, the level of FSH and LH fall quickly over time, and the corpus luteum subsequently atrophies. Falling levels of progesterone trigger menstruation and the beginning of the next cycle.

• The menstrual cycle is a monthly cycle in which the primate females ovulate once in a month.
• Menstruation is important because it prepares the body for the fertilization and is a key process in reproduction.
• The cycle occurs in humans, chimpanzees and Orangutans, gorillas and monkeys.
• Other mammals have a similar cycle which is known as the oestrous cycle.

If fertilization does not occur, progesterone inhibits LH from pituitary.

If fertilization does not occur in the uterus, the corpus luteum will involute and there will be a drop in the hormone levels, which will cause the uterus to shed its lining and egg in the process called menstruation, where there is blood and uterine secretions are removed through the vagina.
Therefore, the correct answer is option C.

Menarche is the first occurrence of menstruation and marks the beginning of the reproductive period.
Menopause is the end of menstruation and marks the end of the reproductive period of women.
Therefore, the correct answer is option A.

Menstrual cycle is rhythmic reproductive cycle in which the endometrium wall of uterus forms placenta. Placenta provides nourishment to the developing fetus if implantation occurs. If pregnancy does not occur, this endometrial lining is shred off, known as menstruation. So, this endometrium thickening is not permanent.
Thus, the correct answer is option B.

Puberty is the stage at which physical changes occurs through which a child's body matures into an adult body to enable fertilization.
Pubertal changes in girls is secondary sexual characteristics which involves development of breast, pubic hair, changes in vagina, uterus and ovaries, menstruation, development of acne due to hormonal changes.
Thus, the correct answer is option D.

Ovulation is the process when a mature egg is released from the ovary. Then the egg is pushed down the Fallopian tube and is available to be fertilized. In females, ovulation continues after the age of 45-50 after which eggs are not released from the ovary and there is menopause.
Thus, the correct answer is option (A), '45-50'.

• Menstruation also is known as a monthly bleeding cycle that occurs in a female. During the period of 21-28 days oviduct, a part of the female reproductive system produces an egg in the process called ovulation. In this duration, the uterus prepares itself by increasing blood supply with arteries and veins, building a placenta to support the embryo if the egg gets fertilized by a sperm. If the egg is not fertilized the uterus starts contractions to break down the placenta. This process of rupturing the placenta from the uterus wall goes on for 3-5 days and is called menstruation. 
  
• Luteinization is an early step in the formation of griffin follicles, an early stage of a mature ovum.
• Oogenesis is a complete process by which egg/ovum is formed.
• Estrogeniztion is the production of thick pale fluid produced by the action of estrogen during puberty in females.

If fertilized egg is not implanted into the uterus after the release of the matured egg, the corpus luteum degenerates and the levels of estrogen and progesterone decrease. The decrease in the level of progesterone causes the endometrium to degenerate initiating the menstrual cycle. This causes the hypothalamus to stimulate the release of GnRH, which in turn causes the release of LH and FSH from the anterior pituitary. The rising level of LH and FSH causes the growth of follicles on the ovarian surface, preparing for ovulation and thus beginning the ovarian cycle. So, the correct option is 'hypothalamus stimulates the anterior pituitary to increase its output of FSH and LH'.

Menopause is the time when menstrual cycles permanently cease. Symptoms of menopause include irregular periods, hot flashes, vaginal dryness, mood swings. During natural menopause, estrogen and progesterone levels in blood decreases. However, the levels of FSH and LH in blood increases during this time. High levels of FSH is an indicator of perimenopause period.

The average length of a human menstrual cycle is 28 days, although it can vary between individuals.

Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a boy.
Menopause is defined as the absence of menstrual periods for 12 months. It is the time in a woman's life when the function of the ovaries ceases. The process of menopause does not occur overnight, but rather is a gradual process. 
At conception, gender is determined by chromosome characteristics and it will be the male (or rather the male's sperm) that dictates whether the baby will be a boy or a girl. Prior to conception, the unfertilized egg carries an X chromosome while the sperm can carry either an X or a Y chromosome. The gender of the baby comes down to one simple event. If the sperm carrying an X chromosome fertilizes the egg, a girl will be conceived. If the sperm carrying a Y chromosome fertilizes the egg, a boy will be conceived.
A goitre is a swelling of the neck or larynx resulting from enlargement of the thyroid gland (thyromegaly), associated with a thyroid gland that is not functioning properly.Worldwide, the most common cause for goitre is iodine deficiency, usually seen in countries that do not use iodized salt.