Menstrual Cycle - Phases Of Menstrual Cycle And Role of Hormones: Overview, Phases

The menstrual cycle is a natural and regular process that happens in the female body. It prepares the female body for pregnancy every month. The cycle has four phases- menstrual, follicular, ovulatory, and luteal. Each phase has different changes in the body. According to the International Federation of Gynecology and Obstetrics (FIGO), normal menstrual cycles should have consistent frequency, regularity, duration, and volume of flow. The menstrual cycle is an important sign of reproductive health in women.

This Story also Contains

1. Definition Of The Menstrual Cycle
2. Anatomy And Physiology Of The Female Reproductive System
3. Phases Of The Menstrual Cycle
4. Role Of Hormones In The Menstrual Cycle
5. Common Menstrual Disorders
6. MCQS on Menstrual Cycle
7. Recommended Video On 'Menstrual Cycle'

The menstrual cycle is the monthly sequence of changes a woman’s body goes through in preparation for the possibility of pregnancy. Oogenesis is the process of egg formation that prepares the ovary for each menstrual cycle. Hormonal changes cause menstrual bleeding. This article covers Menstrual Cycle, Anatomy, and Physiology of the Female Reproductive System, Phases of the Menstrual Cycle. The menstrual cycle is a key part of human reproduction, helping the body get ready for pregnancy.

Definition Of The Menstrual Cycle

The menstrual cycle is a natural biological process by which the female body gets prepared every month for pregnancy. It is changes that occur in the ovaries and lining of the uterus and are regulated by hormonal fluctuations. Pregnancy-parturition-lactation are stages that replace the menstrual cycle after successful fertilisation in humans and implantation.

Commonly, the length of the menstrual cycle is about 28 days, although, in adults, it can also be anywhere between 21-35 days. This variability can be attributed, at least in part, to factors such as stress, diet, or general health. It undergoes four major phases: menstrual, follicular, ovulation, and luteal phases, each with peculiar hormonal changes and physiological events.

Anatomy And Physiology Of The Female Reproductive System

The female reproductive system includes some very fundamental organs that relate to each other to provide for the menstrual cycle and reproduction. The female external genital organs help in the release of menstrual blood during the menstrual cycle.

Anatomy of the Female Reproductive System

• Ovaries: Small, almond-shaped glands that produce eggs (ova) and secrete hormones, including estrogen and progesterone.

• Fallopian Tubes: Tubes that convey the egg from the ovary to the uterus; the site where fertilization generally occurs.

• Uterus: A hollow, muscular organ where a fertilized egg implants and develops into a fetus.

• Cervix: The lower portion of the uterus that opens into the vagina; it produces mucus which changes in consistency during the menstrual cycle.

• Vagina: A muscular canal connecting the cervix to the outside of the body; functions as a birth canal and the exit for menstrual blood.

Basic Physiology

• Ovarian function refers to the production of eggs and hormones, namely estrogen and progesterone, that control the menstrual cycle.

• Uterine function refers to the preparation of the lining of the uterus, endometrium, and its shedding during menstruation if implantation does not occur.

Phases Of The Menstrual Cycle

The different phases of the menstrual cycle include four distinct phases. All these phases are hormonally mediated and oriented toward preparing the body for the pregnancy-parturition-lactation cycle.

Menstrual Phase

• Duration: Day 1 to Day 5

• Endometrial shedding: The lining of the uterus is lost and leads to menstrual bleeding.

• Symptoms and biological changes: Cramps, bloating, and mood swings are some of the common complaints during this phase.

• Hormonal levels: Estrogen and progesterone levels are low.

Follicular Phase

• Duration: Day 1 to Day 13

• Follicle development in the ovaries: Many follicles start maturing, but usually only one is going to develop fully.

• Role of FSH: Follicle Stimulating Hormone stimulates the growth of ovarian follicles.

• Increased estrogen secretion: As follicles mature, they begin to secrete a greater amount of estrogen.

• Thickening of the endometrial lining: The thickness of the uterine lining begins to increase in anticipation of an impending pregnancy.

Ovulation Phase

• Duration: Day 14

• Release of the egg from the ovary: The ovary releases the mature egg into the fallopian tube.

• Surge in LH: Luteinizing Hormone surges to its peak, followed by ovulation.

• Role of estrogen and progesterone: Estrogen peaks a little before ovulation, whereas progesterone starts increasing after ovulation.

• Signs of ovulation: Basal body temperature increases, the cervical mucus changes and there may be mild pelvic pain.

Luteal Phase

• Duration: Day 15 to Day 28

• Formation of corpus luteum: The ruptured follicle is now known as the corpus luteum. It secretes progesterone.

• Secretion of progesterone and estrogen: These hormones prepare the endometrium for implantation.

• Endometrial preparation for possible implantation: The lining of the uterus becomes thick and rich in nutrients.

• Hormone levels drop in the absence of fertilisation: In the absence of fertilization, estrogen and progesterone levels fall.

• Premenstrual symptoms: These can include mood changes, breast tenderness, and bloating.

Role Of Hormones In The Menstrual Cycle

Hormones are what essentially control the menstrual cycle and each hormone participates at different times during the cycle or in different phases of buildup and breakdown.

Estrogen

• Production sites: Principally produced in the ovaries.

• Functions during the menstrual cycle: Causes growth of the endometrium and acts as a negative feedback on the release of FSH and LH.

• Effects on secondary sexual characteristics: Breast development, body fat distribution, and the menstrual cycle.

Progesterone

• Production sites: Progesterone is produced in the corpus luteum of the ovary.

• Functions during the menstrual cycle: Prepare the endometrium for implantation and later maintain early pregnancy.

• Role in pregnancy: Maintains the uterine lining and prevents contractions.

Follicle Stimulating Hormone (FSH)

• Production site: Pituitary gland

• Role in follicular development: Stimulates the growth and maturation of ovarian follicles.

Luteinizing Hormone (LH)

• Production site: Pituitary gland

• Role in ovulation: Triggers the release of a mature structure of ovum from the ovary.

Gonadotropin-releasing Hormone (GnRH)

• Role in the regulation of FSH and LH: GnRH from the hypothalamus regulates the release of FSH and LH from the pituitary gland.

• Feedback mechanisms: Estrogen and progesterone levels control GnRH release through negative feedback loops.

Common Menstrual Disorders

Disorders of the human reproductive system, like PCOS or hormonal imbalance, can disturb the normal menstrual cycle.

• Dysmenorrhea: Pain at the beginning of menstruation, often consisting of abdominal cramps.

• Amenorrhea: Absence of menstruation, either primary (never started) or secondary (stopped).

• Menorrhagia: Excessive bleeding at menstruation.

• Premenstrual Syndrome (PMS): A collection of symptoms, including mood swings, bloating, irritability, and more, that occurs a week or more before menstruation.

• Polycystic Ovary Syndrome (PCOS): A hormonal disorder that causes irregular periods, ovarian cysts, and a variety of other symptoms.

Diagnosis and Treatment

Diagnostic Tests: Ultrasonography, hormone level tests, and physical examinations for the diagnosis of menstrual disorders.

Treatment Options: Medications for pain relief and hormonal treatments, lifestyle modifications involving diet and exercise, and surgical interventions in some cases.

MCQS on Menstrual Cycle

Question: Menstrual bleeding is the result of

1. Low levels of ovarian hormones

2. High level of ovarian hormones

3. High levels of LH

4. High levels of FSH

Answer: Ovarian hormones like progesterone and estrogen contribute to low levels, which triggers menstrual bleeding. These hormones support the healthiness of the endometrium; if their levels reduce, the process of shedding occurs, and a woman experiences menses. That is part of the menstrual cycle, which includes the regulation through several hormones of the pituitary gland-like luteinizing hormone and follicle-stimulating hormone. Menstrual bleeding is usually for 4 to 8 days and is part of the normal features of the menstrual cycle.

Hence, the correct answer is Option (1) Low levels of ovarian hormones.

Question: During menstrual cycle, the shedding of endometrium lining lasts for

1. 10 -12 days average

2. 3-4 days average

3. 7-8 days average

4. 14-16 days average

Answer: Menstruation is a monthly shedding of a female uterus lining; it lasts about 3 to 5 days (average) and contains blood and tissue that exits the body through the cervix and vagina.

Hence, the correct option is option 2) 3-4 days average

Question: Ovulation in human females normally takes place during the menstrual cycle.

1. At the mid secretory phase

2. Just before the end of the secretory phase

3. At the beginning of the proliferative phase

4. At the end of the proliferative phase

Answer: Menstruation is the shedding of the uterine lining in adult females approximately every 28 to 29 days. The cycle is essential for egg production and preparing the uterus for potential pregnancy. Menarche or the beginning of menstruation typically occurs between the ages of 12 and 15 years. The ovarian cycle is made up of the follicular phase, ovulation, and luteal phase, while the uterine cycle includes menstruation, proliferative phase, and secretory phase. The LH and FSH hormones cause the Graafian follicle to change into corpus luteum on day 14.

Hence, the correct answer is Option (4) at the end of the proliferative phase.

Recommended Video On 'Menstrual Cycle'