Human Reproduction and Contraception

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

Menstrual cycles occur in primates such as humans, apes, and chimpanzees, as well as old-world monkeys. Lemurs, which are prosimians, have an estrous cycle instead of a menstrual cycle.

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. 

Progesterone is a hormone released by the corpus luteum in the ovary. It plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. It may also be involved in the growth of certain cancers. During the menstrual cycle, when an egg is released from the ovary at ovulation (approximately day 14), the remnants of the ovarian follicle that enclosed the developing egg form a structure called as the corpus luteum. This releases progesterone and, to a lesser extent, oestradiol. The progesterone prepares the body for pregnancy in the event that the released egg is fertilised. If the egg is not fertilised, the corpus luteum breaks down, the production of progesterone falls and a new menstrual cycle begins. Estrogen or oestrogen is the primary female sex hormone and is responsible for development and regulation of the female reproductive system and secondary sex characteristics. Follicle stimulating hormone is produced by the pituitary gland. It regulates the functions of both the ovaries and testes. Lack or insufficiency of it can cause infertility or subfertility both in men and women. In females, an acute rise of LH ("LH surge") triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell–stimulating hormone (ICSH), it stimulates Leydig cell production of testosterone. It acts synergistically with FSH. 

The clot is made up of blood cells, fibrins and endometrial tissues. Since the blood passes from uterus quickly then there is no time for anticoagulants to act. So, clots cannot be formed easily.

The menstrual cycle is the cycle of natural changes that occurs in the uterus and ovary as an essential part of making sexual reproduction possible. The length of it is an average of 28 days. So, blank 1 is 28 days.
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction, It leads to the beginning of menstrual cycles in women. So, blank 2 is the menstrual cycle.
Menarche is the first menstrual cycle in females. So, blank 3 is menarche.
This cycle begins generally at the age of 12-13 and ends at the age of 45-55. So, option 4 is 45-50.
Menopause marks the end of menstrual cycle. So, blank 5 is menopause.
At around mid-cycle, when the egg is mature, it gets released from the ovary, pushed down to fallopian tube and is available to be fertilized in the process called ovulation. This occurs around 13th-14th day. So, blank 6 is 13$^{th}$ or 14$^{th}$ day and blank 7 is ovulation.
Progesterone is an endogenous steroid hormone and is secreted in the ovaries by the corpus luteum. So, blank 8 is progesterone.
After being released from the ovary, the egg is swept into the fallopian tube by the fimbria, which is a fringe of tissue at the end of each fallopian tube. So, blank 9 is fallopian tube
Thus, the correct answer is option (A), '(1) 28 days, (2) puberty, (3) menarche, (4) 45-50 years, (5) menopause, (6) 13th or 14th days, (7) ovulation, (8) progesterone, (9) fallopian tube'.