RBSE Solutions Class 12 Biology Chapter 34 Menstrual Cycle in Woman

RBSE Class 12 Biology Chapter 34 Multiple Choice Questions

Question 1. The reproductive cycle in a mammalian female is called –
(a) Oestrous cycle
(b) Menstrual cycle
(c) Both of the above
(d) None of the options
Answer: (c) Both (a) and (b)
In simple words: The breeding process in female mammals involves cycles like the oestrous cycle and the menstrual cycle, which are both types of reproductive cycles.

🎯 Exam Tip: Remember that both oestrous and menstrual cycles are part of a female mammal's reproductive process, differing mainly in the shedding of the uterine lining.

Question 3. During the menstrual cycle, how many days the menstruation occurs.
(a) 3 - 5 days
(b) 8 - 12 days
(c) 13 - 20 days
(d) 26 - 30 days
Answer: (a) 3 - 5 days
In simple words: Menstruation, which is the bleeding phase of the menstrual cycle, usually lasts for about 3 to 5 days.

🎯 Exam Tip: Know the typical duration of each phase in the menstrual cycle, especially the menstruation period, as it's a common fact-based question.

Question 4. The essential hormone for ovulation is –
(a) FSH
(b) LH
(c) Estrogen
(d) Oxytocin
Answer: (b) LH
In simple words: Luteinizing Hormone (LH) is the main hormone that causes an egg to be released from the ovary, a process called ovulation.

🎯 Exam Tip: Understand the roles of key hormones (FSH, LH, Estrogen, Progesterone) in the menstrual cycle. LH surge is crucial for ovulation.

Question 5. Essential hormone for milk ejection is –
(a) FSH
(b) LH
(c) Estrogen
(d) Oxytocin
Answer: (d) Oxytocin
In simple words: Oxytocin is the hormone that helps release milk from the breasts when a baby feeds, making it essential for milk ejection.

🎯 Exam Tip: Differentiate between hormones involved in milk production (Prolactin) and milk release (Oxytocin) to avoid confusion.

RBSE Class 12 Biology Chapter 34 Very Short Answer Type Questions

Question 1. In Loading [MathJax]/extensions/MathMenu.js completes?
Answer: The primary reproductive cycles found in mammalian females are the Menstrual cycle and the Estrus cycle.
In simple words: Menstrual and estrus cycles are the two main reproductive cycles.

🎯 Exam Tip: Be able to name and briefly distinguish between the menstrual cycle and the estrous cycle, as they are fundamental concepts in reproductive biology.

Question 3. Which hormone secretes during parturition?
Answer: During parturition, which is the process of childbirth, the hormones Oxytocin and Relaxin are secreted. Oxytocin helps with uterine contractions, and Relaxin helps to widen the birth canal.
In simple words: Oxytocin and Relaxin hormones are released when a baby is born.

🎯 Exam Tip: Identify the specific roles of Oxytocin (uterine contractions) and Relaxin (pelvic ligament relaxation) during childbirth for a complete answer.

Question 4. Which hormones are secreted during the gestation period?
Answer: During the gestation period, or pregnancy, the main hormones secreted are Progesterone and Luteinizing Hormone (LH). Progesterone helps maintain the pregnancy, while LH plays a role in ovarian function related to pregnancy.
In simple words: Progesterone and LH are secreted during pregnancy.

🎯 Exam Tip: Remember that progesterone is critical for maintaining the uterine lining during gestation, and LH has supporting roles in ovarian hormonal regulation.

RBSE Class 12 Biology Chapter 34 Answer Type Questions

Question 1. What is Estrous cycle?
Answer: The Estrous cycle is the reproductive cycle seen in most eutherian mammalian females, excluding primates. This cycle prepares the female's body for mating and pregnancy.
Some key features of the estrous cycle include:
• Mammalian females that have only one estrous cycle in a single breeding season are called monoestrous. Examples include dogs, foxes, bats, and deer.
• Mammalian females that experience two or more estrous cycles in one breeding season are known as polyestrous. Examples are rats, squirrels, cows, pigs, horses, cats, sheep, and rabbits.
• The estrous cycle can be studied by looking at vaginal smears.
• The length of the different phases of the estrous cycle changes between species. For instance, in rats, it lasts 4 to 5 days, while in rabbits, it is 16 to 17 days.
The phases of the estrous cycle are:
1. Diestrus phase: During the non-breeding season, the female stays in the diestrus phase, a period of sexual inactivity.
2. Proestrus phase: This is the shortest phase, lasting from 1/2 an hour to 5 hours. There is no growth of ovarian follicles during this time. Vaginal smears show epithelial cells, and the uterine glands and wall begin to grow thicker and more contractile.
3. Oestrous phase: This phase lasts 9 to 15 hours in rats and is also known as the "heat period." During this time, the body's basal temperature increases, Graffian follicles form in the ovary, and ovulation occurs. The vaginal smear contains cornified cells, and estrogen levels in the blood are at their highest.
4. Post-Estrus or Metestrus phase: This phase lasts 10 to 14 hours. Vaginal smears show cornified cells and leukocytes. Progesterone levels in the blood are at their peak. The corpus luteum forms in the ovaries. If fertilization happens, the female stays in metestrus until childbirth. If there is no fertilization, the estrous cycle repeats after childbirth.
In simple words: The estrous cycle is the reproductive cycle in most mammals (not primates) that prepares them for mating. It has different stages like diestrus, proestrus, oestrus (heat period with ovulation), and metestrus. Its length varies by animal.

🎯 Exam Tip: When describing the estrous cycle, define it, mention examples of monoestrous and polyestrous animals, and briefly explain the key events in each phase.

Question 2. What is the Menstrual cycle?
Answer: The Menstrual cycle is the reproductive cycle found exclusively in primate females (like humans and chimpanzees).
• In women, the menstrual cycle typically begins around 12 years of age, a stage called menarche.
• The cycle naturally stops between 45 to 50 years of age, which is known as menopause.
The menstrual phase consists of four main phases:
1. Menstrual phase: During this phase, blood, along with the unfertilized egg and parts of the uterine lining, is released from the body. The ovary contains immature follicles and corpus albicans. During this time, the body has lower levels of estrogen, and progesterone is almost absent.
2. Follicular phase or Proliferative phase: This phase lasts for 8 to 10 days. Estrogen levels in the blood are at their highest. Graffian follicles develop in the ovary by the end of this phase. The uterine wall becomes thicker, with more blood vessels and glands. Blood FSH levels increase, while blood LH levels decrease.
3. Ovulatory phase or recovery phase: Ovulation, the release of an egg, usually happens around the 14th day (plus or minus 2 days) in a woman. The ovary has a burst Graffian follicle, and FSH and estrogen levels decrease slightly.
4. Luteal phase or secretory phase: This is also called the pre-menstrual phase and is the longest, lasting 12 to 16 days in a woman. The ovary contains a fully developed corpus luteum. The myometrium and endometrium (uterine layers) are at their maximum development. Estrogen, progesterone, and LH levels are highest in the blood. Uterine glands are fully developed and corkscrew-shaped. If fertilization does not occur, the menstrual cycle repeats.
In simple words: The menstrual cycle is a monthly reproductive process in primate females, starting at menarche and ending at menopause. It has four phases: menstrual (bleeding), follicular (egg growth), ovulatory (egg release), and luteal (preparing for pregnancy or next cycle).

🎯 Exam Tip: Clearly define the menstrual cycle and then describe each of its four phases, mentioning key hormonal changes and ovarian/uterine events in each. Distinguish it from the estrous cycle by mentioning primates.

Question 3. Which is the Ovulation phase?
Answer: The Ovulation phase is typically part of the Oestrous phase or recovery phase in reproductive cycles. It is the time when an egg is released from the ovary.
Key characteristics associated with this phase include:
• It is a phase of the Menstrual cycle.
• Its duration in a rat is around 9 to 15 hours.
• It is also known as the "heat period."
• The body's basal temperature increases.
• Graffian follicles form in the ovary, leading to the release of the egg.
• Vaginal smears show the presence of cornified cells.
• Estrogen levels in the blood reach their maximum.
• Ovulation, the actual release of the egg, takes place.
In simple words: The ovulation phase is when a mature egg is released from the ovary, often called the "heat period," and it involves high estrogen levels.

🎯 Exam Tip: Focus on the release of the egg as the central event of the ovulation phase and mention associated hormonal peaks and physical signs.

RBSE Class 12 Biology Chapter 34 Essay Type Questions

Question 1. Describe the Menstrual cycle in detail.
Answer: The Menstrual cycle is the complex reproductive cycle unique to primate females (including humans). It involves regular changes in the ovaries and uterus, preparing the body for potential pregnancy.
• The cycle begins in females at an age of approximately 12 years, a stage called menarche.
• It naturally stops between 45 to 50 years of age, a phase known as menopause.
• The average duration of the menstrual cycle is 28 to 30 days in women and about 35 days in chimpanzees.
The menstrual cycle is divided into four main phases:
1. Menstrual phase: This is the first phase, where blood, along with the unfertilized egg and parts of the uterine lining (endometrium), is shed and released from the body. During this time, the ovary contains immature follicles, and levels of estrogen are low, with progesterone being almost absent.
2. Follicular phase (Proliferative phase): Lasting 8 to 10 days, this phase is marked by the growth of Graffian follicles in the ovary. Estrogen levels in the blood are at their highest, causing the uterine wall to thicken and develop more blood vessels and glands, preparing it for a fertilized egg. Blood FSH increases, while LH decreases.
3. Ovulatory phase (Recovery phase): Around the 14th day of the cycle (with a variation of +/- 2 days), ovulation occurs, meaning an egg is released from the burst Graffian follicle in the ovary. Both FSH and estrogen levels show a slight decrease around this time.
4. Luteal phase (Secretory phase): This is the longest phase, lasting 12 to 16 days, and is also known as the pre-menstrual phase. After ovulation, the ruptured follicle transforms into a fully developed corpus luteum in the ovary. The uterine layers (myometrium and endometrium) reach their maximum development, becoming thick and rich in blood supply. Hormones like estrogen, progesterone, and LH are at their highest levels in the blood. If no fertilization occurs, the corpus luteum degenerates, hormone levels drop, and the cycle repeats with the start of the menstrual phase.
In simple words: The menstrual cycle is a monthly process in primate females, starting at menarche and ending at menopause. It has four parts: menstrual (bleeding), follicular (egg matures), ovulatory (egg releases), and luteal (uterus prepares for pregnancy).

🎯 Exam Tip: For a detailed essay, ensure you cover the definition, key events, hormonal regulation, and specific characteristics of each of the four phases of the menstrual cycle.

Question 2. Write an essay on Parturition in Human.
Answer: Parturition is the process of giving birth to young ones after the completion of embryonic development inside the mother's uterus. In humans and rabbits, as in other eutherian mammals, this marks the end of gestation.
• The period between fertilization and parturition is called gestation. This duration varies greatly among different species.
• For instance, in rabbits, gestation lasts 28 to 30 days, resulting in young ones that are born hairless, blind, and deaf, but they become normal in 5 to 7 days. In humans, gestation typically ranges from 270 to 280 days.
• Parturition is a complex hormonal process. When the levels of FSH (Follicle-Stimulating Hormone) increase, it restarts oogenesis (egg formation).
• Oxytocin is a crucial hormone in parturition, causing strong contractions of the uterine muscles. These contractions create "labour pains" and help push the fetus into the vagina.
• Relaxin is another important hormone. In humans, it is secreted by the corpus luteum, and in rabbits, by the placenta. Relaxin helps widen the birth canal by relaxing the pubic symphysis of the pelvic girdle, providing a broader passage for the baby to pass through.
In simple words: Parturition is the process of childbirth. It involves hormones like Oxytocin, which causes uterine contractions, and Relaxin, which helps widen the birth canal. The length of pregnancy (gestation) differs in various animals.

🎯 Exam Tip: When writing about parturition, define it, mention the gestation period, and explain the roles of key hormones like Oxytocin (contractions) and Relaxin (widening birth canal).

Question 3. Write an essay on Lactation in Human.
Answer: Lactation is the process of milk production and secretion from the mammary glands in humans. This process is vital for nourishing the newborn.
• Prolactin (PRL) hormone, secreted by the anterior pituitary gland, is responsible for the development of mammary glands from the 5th week of gestation until parturition. It also promotes the secretion of milk from the breasts after the baby's birth.
• Human Chorionic Somatotropin (HCST) also plays a helpful role in milk secretion.
• Milk secretion follows a pathway: milk is produced in alveoli, travels through ductules to mammary ducts, then to mammary sinuses, and finally to the lactiferous ducts before being sucked by the child from the breast nipple.
• A neuroendocrine reflex is essential for milk secretion. When a newborn child sucks milk, a somatic neural reflex sends signals to the hypothalamus, which then triggers the posterior pituitary to secrete oxytocin.
• Oxytocin hormone is crucial for milk ejection; it contracts the epithelial muscular cells of the mammary gland, helping milk flow through the tubules so the child can receive it.
• While prolactin is responsible for the synthesis (making) of milk in the mammary glands, oxytocin is responsible for the actual secretion (release) of milk.
• Milk secretion is a Conditional reflex, meaning it happens due to the combined action of the Suckling reflex (triggered by the baby's sucking) and the Ejection reflex (triggered by oxytocin).
• Breastfeeding is highly recommended for at least the first 6 months after birth for the baby's proper growth and development.
In simple words: Lactation is how mothers make and release milk for their babies. Prolactin helps make the milk, and Oxytocin helps release it. Breastfeeding is very important for a baby's health.

🎯 Exam Tip: In an essay on lactation, describe the hormones involved (Prolactin for production, Oxytocin for ejection), the milk flow pathway, and the importance of breastfeeding for infant development.