Menstrual Cycle Overview

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Questions and Answers

What is the average age range for menarche?

10-14 years

12-16 years

8-16 years (correct)

8-12 years

Which hormone is primarily responsible for stimulating the secretion of gonadotropins from the pituitary gland?

Progesterone

Gonadotropin-releasing Hormone (correct)

Luteinizing Hormone

Follicle Stimulating Hormone

What is the average length of a menstrual cycle considered to be?

30 days

28 days (correct)

35 days

21 days

Which of the following is not a pituitary gonadotropin?

Estrogen Signup and view all the answers

What hormonal change occurs at menopause?

Absence of menstrual cycles Signup and view all the answers

Which factors can influence the timing of menarche?

Hereditary and diet Signup and view all the answers

What is considered premature menopause?

Before age 45 Signup and view all the answers

What is the role of the hypothalamus in the menstrual cycle?

Stimulates secretion of gonadotropin-releasing hormone Signup and view all the answers

What is the main function of follicle-stimulating hormone (FSH) during the menstrual cycle?

Stimulate estrogen secretion and follicle maturation Signup and view all the answers

Which phase of the ovarian cycle occurs between day 1 and day 13?

Follicular phase Signup and view all the answers

At what point does the luteinizing hormone (LH) typically peak during the menstrual cycle?

Day 12 or 13 Signup and view all the answers

What triggers the ovulation process during the ovarian cycle?

LH surge Signup and view all the answers

What transformation does a ruptured Graafian follicle undergo after ovulation?

It develops into a corpus luteum Signup and view all the answers

What hormone inhibits the release of prolactin during the menstrual cycle?

Follicle-stimulating hormone (FSH) Signup and view all the answers

What happens to the corpus luteum if the ovum is not fertilized?

It degenerates to corpus albicans Signup and view all the answers

During which phase of the ovarian cycle is a mature ovum released?

Ovulatory phase Signup and view all the answers

Why is the role of prolactin in ovulation control considered unclear?

Its exact function post-fertilization is not well defined Signup and view all the answers

How does an increase in estrogen levels affect FSH secretion?

It decreases FSH secretion Signup and view all the answers

Which of the following phases occurs after ovulation in the ovarian cycle?

Luteal phase Signup and view all the answers

What hormonal change triggers the growth of multiple follicles early in the follicular phase?

Increase in follicle-stimulating hormone (FSH) Signup and view all the answers

Where does fertilization of an ovum usually occur?

In the ampulla of the fallopian tube Signup and view all the answers

Which hormone is secreted by the fertilized ovum to maintain the corpus luteum?

Human chorionic gonadotropin (HCG) Signup and view all the answers

What is the main function of the corpus luteum after ovulation?

To produce estrogen and progesterone Signup and view all the answers

What initiates the menstrual cycle?

Degeneration of the corpus luteum Signup and view all the answers

What is the average blood loss during menstruation?

50-80 ml Signup and view all the answers

What initiates the formation of a new layer of endometrium?

Estrogen Signup and view all the answers

Which phase of the uterine cycle is characterized by the production of progesterone?

Secretory phase Signup and view all the answers

How long does normal menstruation typically last?

3-5 days Signup and view all the answers

What role does progesterone play during the secretory phase?

Supports endometrial receptivity Signup and view all the answers

What happens to the endometrium just before ovulation?

It thickens and becomes more vascular Signup and view all the answers

Which component is NOT part of menstrual flow?

Progesterone Signup and view all the answers

Which hormone is primarily responsible for maintaining the function of the corpus luteum?

Luteinizing hormone Signup and view all the answers

Study Notes

Introduction

The menstrual cycle is the process that involves an egg ripening and being released, while the uterus prepares for a possible pregnancy.
The cycle occurs repeatedly between menarche and menopause.
Menarche marks the first menstrual period in a woman's life.
The average age of menarche is 12-13 years.
Menarche between 8 and 16 years is considered normal.
Factors such as genetics, diet, and overall health can influence the timing of menarche.
The average length of menstrual cycle is 28 days, although it can vary from 21 to 35 days.
Menopause marks the end of the menstrual cycles, with an average age of 52.
Menopause between 45 and 55 is considered common.
Menopause before the age of 45 is termed premature.

Endocrine Control of Menstrual Cycle

The hypothalamus secretes gonadotropin-releasing hormone (GnRH) which stimulates the pituitary gland to release hormones.
The pituitary gland secretes Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH).
The ovaries produce estrogen and progesterone.

Hypothalamic-Pituitary-Ovarian Axis

The hypothalamus regulates the secretion of hormones from the pituitary gland.
GnRH released from the hypothalamus stimulates the pituitary gland.
The pituitary gland controls ovarian function through FSH and LH.
Prolactin is another hormone released by the pituitary gland.

Follicle-stimulating hormone (FSH)

Secreted towards the end of the previous menstrual cycle, peaking at day 5 and again at day 12.
Responsible for follicle ripening and maturation, estrogen secretion from follicles, and ovulation alongside LH.

Luteinizing hormone (LH)

Constant throughout the cycle with a peak around day 12-13.
Promotes follicle ripening with FSH.
LH surge triggers ovulation.
Creates the corpus luteum from the ruptured follicle.
Stimulates estrogen and progesterone production from the corpus luteum.

Prolactin

Its release is inhibited by FSH and LH.
Its exact role in ovulation is unknown but may prevent further ovulation after fertilization.

Physiology of Menstrual Cycle

The normal menstrual cycle is divided into the ovarian cycle and the uterine cycle.
The ovarian cycle consists of the follicular phase, ovulation, and luteal phase.
The uterine cycle consists of menstruation, the proliferative phase, and the secretory phase.

The Ovarian Cycle

The ovarian cycle represents changes in the ovary through three stages: follicular phase, ovulatory phase, and luteal phase.

Follicular Phase (day 1-13)

Primordial follicles mature into Graafian follicles under FSH influence.
Usually, only one follicle matures fully, while others regress.
The empty follicle becomes the corpus luteum, which eventually atrophies into the corpus albicans.
The Graafian follicle produces increasing amounts of estrogen, inhibiting FSH secretion.

Ovulatory Phase (day 14)

This stage releases a mature ovum from the ovarian follicle into the fallopian tube; LH surge starts around day 12 and lasts 48 hours.
The mature ovum measures 20 mm.
Fimbriae sweep the ovum into the fallopian tube.
An unfertilized ovum disintegrates in the fallopian tube after about a day.
Fertilization takes place in the ampulla of the fallopian tube.
A fertilized ovum begins embryo development.

Luteal Phase (day 15-28)

This marks the final stage of the ovarian cycle.
The corpus luteum produces estrogen and progesterone.
If fertilization doesn't occur, the corpus luteum degenerates into the corpus albicans, decreasing estrogen and progesterone levels.
Menstruation begins due to the hormone drop.
If fertilization happens, the fertilized ovum releases human chorionic gonadotropin (HCG), preventing corpus luteum degeneration.
The corpus luteum continues to produce estrogen and progesterone, preventing menstruation, indicating pregnancy.

Menstrual Cycle and Feedback Mechanism

Positive and negative feedback loops regulate hormone levels.
Low estrogen levels encourage the hypothalamus to release more GnRH (positive feedback).
Increased GnRH stimulates the pituitary to release more FSH (positive feedback).
High estrogen levels inhibit GnRH production (negative feedback).

The Uterine Cycle

The uterine cycle consists of three phases: menstruation, proliferative phase, and secretory phase.

Menstruation

This marks the first phase of the uterine cycle.
It represents the shedding of the endometrium, resulting in blood loss, signaling the lack of pregnancy.
Degeneration of the corpus luteum triggers menstruation.

Menstrual Flow

Duration is typically 3-5 days (normal range: 2-7 days).
Average blood loss is 50-80 ml.
Color: dark red.
Composition: RBCs, cervical mucus, epithelial cells, and bacteria.

Proliferative Phase

In this phase, estrogen causes the endometrium to grow and proliferate.
Maturing follicles release increasing oestradiol levels.
Estrogen develops a new layer of endometrium in the uterus and stimulates cervical mucus production.

Secretory Phase

The corpus luteum secretes progesterone during this phase, preparing the endometrium for blastocyst implantation and early pregnancy support.
Progesterone increases blood flow, uterine secretions, and reduces uterine smooth muscle contractility.

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Description

Explore the fundamental aspects of the menstrual cycle, including key events from menarche to menopause. Understand the hormonal regulation involved and the typical duration of menstrual cycles. This quiz is designed to test your knowledge on women’s reproductive health.