RBSE Solutions For Class 12 Biology Chapter 34: Menstrual Cycle in Human | Textbook Important Questions & Answers

RBSE Class 12 Biology Chapter 34- Menstrual Cycle in Humans. In this chapter, students can learn in detail about the different phases of the menstrual cycle, follicular phase, ovulatory phase and post-ovulatory phase. It also deals with parturition, lactation and hormones responsible for lactation and the synthesis of milk.

These important questions help students to perform exceptionally well in their exams. By practising these important questions, students can analyze their preparation, get a thorough knowledge about all the important terminologies and perform their best in the examinations.

RBSE Solutions for Class 12 are the best study material for both class assignments and other board examinations. By practising these important questions, students can gain deep knowledge about the topics explained in this chapter and also help them to be well prepared for their upcoming examinations.

RBSE Class 12 Biology Chapter 34 Important Questions

RBSE Biology Chapter 34: MCQ Type Questions

Q.1. How many days is considered a normal menstrual cycle?

(a) 12 days

(b) 18 days

(c) 28 days

(d) 38 days

Sol: (c) 28 days.

Q.2. How many days lasts for menarche during the menstrual cycle?

(a) 4 to 7 days

(b) 8 to 12 days

(c) 13 to 20 days

(d) 26 to 30 days

Sol: (a) 4 to 7 days.

Q.3. Which of the following is the essential hormone required for ovulation?

(a) Follicle-stimulating hormone

(b) Oxytocin

(c) Luteinizing hormone

(d) Estrogen

Sol: (c) Luteinizing hormone.

Q.4.The reproductive cycle in a mammalian female is called _________.

(a) Oestrous cycle

(b) Menstrual cycle

(c) Both of the above

(d) None of the above

Sol: (c) Both of the above.

Q.5.Which of the following is the essential hormone for milk ejection?

(a) Estrogen

(b) Oxytocin

(c) Follicle-stimulating hormone

(d) Luteinizing hormone

Sol: (b) Oxytocin.

Q.6. Which hormone is responsible for the menstrual cycle in women?

(a) Estrogen

(b) Luteinizing hormone

(c) Follicle-stimulating hormone

(d) Oxytocin

Sol: (a) Estrogen

Q.7. Which hormone is responsible for lactation?

(a) Luteinizing hormone

(b) Oxytocin

(c) Follicle-stimulating hormone

(d) Estrogen

Sol: (b) Oxytocin.

Q.8. How many reproductive cycles do female placental mammals have?

(a) One

(b) Two

(c) Three

(d) Four

Sol: (a) One.

Q.9. Which of the following is a follicular phase of a menstrual cycle?

(a) 14th day

(b) 15 to 28 days

(c) 6 to 13 days

(d) All of the above

Sol: (c) 6 to 13 days.

Q.10. Which hormone is responsible for the synthesis of milk in the mammary glands?

(a) Estrogen

(b) Oxytocin

(c) Luteinizing hormone

(d) Prolactin hormone

Sol: (d) Prolactin hormone.

RBSE Biology Chapter 34:Short and Long Answer Type Questions.

Q.1.Which hormone is responsible for the parturition?

Sol: Oxytocin and Relaxin are the two main hormones, which are secreted during parturition and is responsible for the parturition in the female reproductive system

Q.2.Name the reproductive cycles found in the mammalian females.

Sol: Menstrual cycle and Estrus cycle are the reproductive cycles found in the mammalian females.

Q.3. In how many days does one menstrual cycle complete?

Sol: 28 to 30 days is required for one menstrual cycle to complete.

Q.4. Which hormones are secreted during the gestation period?

Sol: Luteinizing hormone (LH) and progesterone are two hormones secreted during the gestation period.

Q.5. What is the estrous cycle?

Sol: Estrous cycle is of short duration. It is related to sexual maturity. Excluding primate mammals. This cycle is found in the rest of all mammals. During this period, the females receive the male for mating.

Q.6. What are the different phases of the menstrual cycle?

Sol: The menstrual cycle in females consists of four main phases:

  1. Menstrual phase.
  2. Follicular phase or proliferative phase.
  3. Ovulatory phase or recovery phase.
  4. Luteal phase or secretory phase.

Q.7. Why does menstruation occur?

Sol: Menstruation is a normal event occurring in women wherein there is normal vaginal bleeding and is a part of a healthy woman’s monthly cycle.

Q.8. What is Parturition?

Sol: Parturition means childbirth. It is also known as labour. It is the mechanism of signalling the onset of labour (or) a procedure of delivering a child after the completion of pregnancy period. The developed child is born with the release of cortisol.

Q.9. List out the three stages of parturition

Sol: There are three stages of Parturition:

  • Dilation.
  • Expulsion.
  • Placental.

Q.10. Which hormones are released during the process of parturition?

Sol: During the process of parturition or the childbirth oxytocin, estrogen and cortisol hormones are released.

Q.11.What are menstrual hormones?

Sol: Hormones are the chemical messengers released by various endocrine glands and are responsible for the various changes in the human body. The hormones, which influence the menstrual in women are called the menstrual hormones. The four-phase of the menstrual cycle is influenced by estrogen, progesterone, follicle-stimulating hormone (FSH) and Luteinizing hormone, which are called the female hormones. The variation in the level of each of these hormones decides the phase which a girl undergoes.

Q.12. What is the ovulation phase?

Sol: The ovulation phase is also called the oestrous phase. It is a phase of the menstrual cycle, whose duration is about 9 to 15 hours. This phase is also called the heat period. During this phase, the basal temperature of the body is increased and results in the formation of Graffian follicles in the ovary. The vaginal smear test shows the presence of cornified cells. There is a maximum rise in the levels of estrogen in the blood and ovulation takes place in the ovulation phase.

Q.13. What is the menstrual cycle?

Sol: The menstrual cycle is found in all primate females. Its duration is from 28 to 30 days in a woman and it varies with the species. In the chimpanzee, the duration of the menstrual cycle is 35 days. In women, the menstrual cycle begins at the age of 12 years, which is called the menarche. The menstrual cycle ceases naturally at the age of 45 to 50 years, which is called the menopause. The menstrual cycle consists of four different phases:

  1. Menstrual phase.
  2. Follicular phase or proliferative phase.
  3. Ovulatory phase or recovery phase.
  4. Luteal phase or secretory phase.

Q.14. What are lactation hormones?

Sol: Hormones like estrogen, placental lactogenic, progesterone, prolactin and oxytocin are involved in the process of lactation.

  1. Estrogen hormone helps in increasing the size of the breast during pregnancy causing the growth of breast tissue.
  2. The presence of a placental lactogenic hormone is higher during pregnancy as this hormone helps in stimulating the growth of the nipple, areola and breast tissue.
  3. Progesterone hormone helps in increasing the size of the breast tissue along with boosting milk production. During the post-pregnancy period, the progesterone hormone level tends to decrease, which stimulates milk production.
  4. Prolactin hormone helps in differentiating the cells that perform their own specific functions. The alveoli, which is responsible for producing milk after the baby’s birth is active mainly because of the prolactin hormone. The prolactin hormone is produced once exposed to cortisol hormone.
  5. Once the nipples are stimulated, the oxytocin hormone is released causing the alveoli to contract. These help in squeezing the milk out into the duct system. The entire process is called a letdown. The letdown process begins only when the nerves of breasts are stimulated.

Q.15. What is the menstrual cycle? Draw a neat labelled diagram showing the different phases of the menstrual cycle.

Sol: The menstrual cycle is the regular and the natural change that occurs in the female reproductive system, which makes pregnancy possible. The cycle is required for the production of oocytes and for the preparation of the uterus for pregnancy.

The below diagrams explains in detail about the different phases of the menstrual cycle.

Phases of the Menstrual Cycle

Q.16. Brief out the process of parturition in humans.

Sol: The process of parturition in the female reproductive system:

  1. In humans and other eutherians, the embryonic development completes within the uterus, which is followed by the birth of the young ones. This natural process is termed parturition.
  2. The duration between the fertilization and the parturition is called gestation. Different species have different gestation. For example, the gestation period in the rabbit is 28 to 30 days, the gestation period in humans is 270 to 280 days.
  3. Parturition is a hormonal process, which involves many hormones. During the completion of the embryonic development, the pituitary gland increases the secretion of follicle-stimulating hormone (FSH) and decreases the secretion of luteinizing hormone (LH) and progesterone hormones.
  4. As a result, the placenta gets dissolved and the fetus separates from the uterine wall. The increased level of FSH restarts oogenesis.
  5. Oxytocin is the primary hormone required during the parturition. The oxytocin hormone causes labour pains by the contraction of the uterine muscles. As a result, the uterus pushes the fetus into the vagina.
  6. The relaxin hormones secreted by the corpus luteum provides a broad passage for the parturition by relaxing pubic symphysis of the pelvic girdle.

Q.17. Brief out the process of lactation in women.

Sol: The process of lactation in women occurs in the following steps:

  • The anterior pituitary gland, which secretes prolactin hormone is responsible for the process of lactation in women.
  • During the gestation period, from the fourth week up to the parturition, is responsible for the growth and development of the mammary glands.
  • Prolactin hormone also promotes the secretion of milk from the breasts after the birth of the child. Besides this, the placenta also secretes human chorionic somatotropin sucks (HCST)which is also helpful in the secretion of the milk.
  • The secretion of the prolactin hormone from the anterior pituitary gland is stimulated by the oxytocin hormone.
  • Up to three days, since the parturition, the secretion of the milk in the mother’s breast is yellow fluid, which is rich in proteins and lactose. The fluid is called colostrum, which contains immunoglobulins (IgA), which develops the innate immunity in the newborn child.
  • The process of lactation is as follows:
  • Milk secretion → Milk → Alveoli Ductal → Mammary duct → Mammary sinus → Lactiferous duct → Breast nipple → Child sucks the milk.
  • The neuroendocrine reflex is required for the milk secretion.
  • Oxytocin hormone secretion from the pituitary gland is responsible for milk secretion.
  • When a newborn baby sucks the milk of the mother, then the somatic neural reflex reaches to the hypothalamus and it initiates oxytocin secretion from the posterior pituitary gland.
  • The posterior pituitary gland facilitates milk ejection by the contraction of the epithelial muscular cells of the mammary gland so that the milk flows into the tubules and the child receives the milk through the nipples.
  • Prolactin secretion of the anterior pituitary is responsible for the synthesis of milk in the mammary glands.
  • While oxytocin hormones are responsible for the milk secretion from the mammary glands.
  • The milk secretion is a conditional reflex in which the milk secretion occurs by the combined action of sucking reflex and ejection reflex.
  • Breastfeeding is essential for six months after parturition for proper development of the child.

Q.18. Describe the process of menstruation occurring in the female reproductive system.

Sol: Menstruation is a normal event occurring in women wherein there is normal vaginal bleeding and is a part of a healthy woman’s monthly cycle.

The process of menstruation in women occurs in the following steps:

  1. A healthy woman undergoes this cycle which lasts for 28 days until she hits menopause.
  2. It occurs as it prepares the body for pregnancy every month through menstruation wherein the uterus lining thickens for the embryo to get embedded once the egg is released from the ovaries.
  3. In the event of fertilization, the future fetus would rest here until the childbirth.
  4. If there is no such event of fertilization, this uterus lining tears leaking through the vagina in the form of menses.
  5. This lasts for about 2-7 days.
  6. If there is no fertilization, there is a dip in the levels of progesterone and estrogen finally touching a level which signals the body to begin menstruation.
  7. Periods are a way by which women release tissues which are no longer needed.

Q.19. Brief out the different phases of the menstrual cycle?

Sol: The menstrual cycle is found in all primate females. Its duration is from 28 to 30 days in a woman and it varies with the different species. The menstrual cycle is found only in primate females. Its duration is 28 to 30 days. In women, the menstrual cycle begins at an age of 12 to 13 years which is called menarche. The menstrual cycle consists of four different phases:

Menstrual phase.

Its duration of this phase is 3 to 5 days. The term menstruation refers to bleeding. During this phase, the blood is released along with the dead ovum and pieces of the uterine endometrium. The ovary has an immature follicle and corpus Albicans. At this stage, the woman’s body has less estrogen and lacks progesterone hormone.

Follicular phase or Proliferative phase.

The duration of this phase is 8 to 10 days. At this stage, there is a maximum estrogen in the blood and the formation of Graffian follicles up to the end of this phase.

The increased thickness of the uterine wall and the increased number of the uterine and the uterine glands.

At this stage, the woman’s body has more Follicle-stimulating hormone (FSH) compared to the Luteinizing hormone (LH).

Ovulatory phase or recovery phase.

In this phase, there is anovulation, which occurs on the 14th + 2 days.

The ovary has burst Graffian follicles.

At this stage, the levels of both the Follicle-stimulating hormone (FSH) and the Luteinizing hormone (LH) are slightly reduced in the blood.

Luteal phase or secretory phase.

This is called the premenstrual phase.

It is the longest phase of the menstrual cycle and its duration in a woman is between 12 to 16 days.

The ovary shows fully developed corpus luteum.

At this stage, there is a maximum development of myometrium and endometrium

At this stage, there is a maximum level of estrogen, progesterone and Luteinizing hormone (LH) in the blood along with the rise in the body temperature.

The uterine glands are completely developed and form a corkscrew-shape.

The female remains in lateral phase till the parturition. If there is no fertilization, the menstrual cycle is repeated.

Q.20. Brief out the different phases of the estrous cycle.

Sol: The oestrous cycle is the set of recurring physiological changes, which are induced by reproductive hormones in most mammalian menarche females. The estrous cycle is of short duration. It is related to sexual maturity. Excluding primate mammals. This cycle is found in the rest of all mammals. During this period, the females receive the male for mating.

The females that exhibit one estrus cycle in one breeding season are called the

monoestrous. For example- Bats, deer, dogs, fox, etc.

The mammalian females which exhibit two or more oestrous cycles in one breeding season are called the polyestrous. For example- Cat, cow, horse, rabbit, rat, sheep, squirrel, pig, etc.

The estrous cycle is studied with the help of vaginal smears. The duration of various phases of the oestrous cycle varies from species to species. For example- in rats, it is from 4 to 5 days and in the rabbit, it is from 16 to 17 days.

The estrous cycle has four phases:

Diestrus phase

  • It is also called an anestrus phase.
  • It is the longest phase and its duration is 60 to 70 hours.
  • The ovary is without Graffian follicles.
  • The uterine gland is thin, small and inactive.
  • The vaginal smear test shows leukocytes.
  • During the non-breeding season, the female remains in the diestrus phase.

Proestrus phase

  • It is the smallest phase, its duration is 1/2 to 5 hours.
  • There is no growth of an ovarian follicles
  • Vaginal smear exhibits epithelial cells.
  • The uterine glands begin to increase in number and size.
  • The thickness and contractility of the uterine wall begins to increase

Oestrous phase

  • Its duration is 9 to 15 hours.
  • It is also called a heat period.
  • The basal temperature of the body is increased.
  • Formation of Graffian follicles in the ovary.
  • The vaginal smear test shows the presence of cornified cells.
  • There is a maximum level of estrogen in the blood.
  • The ovulation takes place.

Post-estrus or metestrus phase

  • Its duration is 10 to 14 hours.
  • The vaginal smear test shows cornified cells and leukocytes.
  • There is a maximum level of progesterone in the blood.
  • Formation of Corpus luteum in the ovaries.
  • If there is fertilization, the females remain in the metestrus phase till the parturition.
  • The oestrous cycle repeats if there is no fertilization and after parturition.

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