Menstrual Cycle Flashcards

1
Q

Menstrual cycle

General

A

Cyclic pattern of hormonal and tissular activity that prepares a suitable uterine environment for the fertilization and implantationof an ovum

Involves both an ovarian and endometrial (uterine) cycle that are dependent on one another

Normal cycle length: 21-35 days
Average cycle length: 28 days

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2
Q

Menarche

A

1st menstrual period; starting on average age at 12years

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3
Q

Perimenopause

A

interval of menstrual irregularities leading up to the total cessation of cycles

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4
Q

Menopause

A

cessation of menses for 12 months or more; average age 51

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5
Q

Ovarian phases

Follicular phase

A

Represents the time during which the ovarian follicle and its oocyte develop

Spans from menses onset (day 1) to the day before the surge of luteinizing hormone (LH), leading to ovulation
Length: 14-21 days

Intervals in cycles usually remain consistent until perimenopause

Follicular phases become shorter and more frequent

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6
Q

Ovarian phases

Luteal phase

A

Represents the time after ovulation when the ovary produces hormones to support a potential pregnancy and maintain a healthy endometrium

Spans from the day of LH surge until the onset of the next menses

Length: 15 days

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7
Q

Endometrial (uterine) phases:

A

Menses:desquamation/shedding of the endometrial lining

Proliferative phase: endometrial proliferation

Secretoryphase: preparation for potential oocyte implantation

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8
Q

Regulation of the Menstrual Cycle

HPO Axis

A

Regulated by thehypothalamic-pituitary-ovarian (HPO) axis

Hypothalamus:
Releases GnRH in a pulsatile fashion → stimulates gonadotropes of the anterior pituitary

Anterior pituitary:
Stimulated by GnRH → releasesFSH and LH
FSH and LH → stimulate theovaries

FSH:
Stimulates follicular development and ovum maturation
Stimulates the ovary (granulosa cells) to produce estradiol

LH:
Stimulatesthe ovary (theca cells) to producetestosterone; most is converted toestradiol
A surge of LH midcycle triggers ovulation

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9
Q

Regulation of the Menstrual Cycle

negative and positive feedback of Ovaries

A

Ovaries:

Negative feedback:During most of the menstrual cycle, estrogens inhibitfurther secretions of FSH, LH, and GnRH

Positive feedback:For a short time midcycle,estradiol stimulates FSH and LH secretion from the pituitary → results in ↑estrogenproduction in theovariesand causes the surge of LH, which triggers ovulation

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10
Q

Regulation of menstrual cycle

Ovaries and Progestins

A

Progestins:
Progesterone secreted by the corpus luteum (stimulated by LH)
Effects on reproductive organs:
Stabilizes and causes maturation of theendometrium→ prepares theendometriumforimplantation
↑ Endometrial secretions (↑ secretion thickness)
Lobular breast development
↑ Body temperature

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11
Q

Regulation of the Menstrual Cycle

Activins and Inhibins

A

Activins:
Secreted by the granulosa cells of the ovarian follicles (stimulated by FSH)
Providespositivefeedback to gonadotropes

Inhibins:
Secreted by the granulosa cells of the ovarian follicles (stimulated by FSH)
Providesnegativefeedback to gonadotropes

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12
Q
Changing concentrations of gonadotropins and estrogens throughout the length of the menstrual cycle: sudden rise in estradiol, LH, and follicle-stimulating hormone (FSH) around day 14 (ovulation), and the rise in progesterone during the luteal phase in anticipation of fertilization and implantation of the ovum.
A
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13
Q

Follicular phase

general

A

Represents the time during which the follicle (and the oocyte it contains) develop, leading up to ovulation
Occurs within the ovaries

Coincides with menses and the proliferative phase of the endometrium

days1–14of the menstrual cycle

Primarily under the control ofestradiol

Increasing amounts of estradiol will lead to negative feedback near the end of the phase

The purpose of the follicular phase is to:
Grow the endometrial layer of the uterus (increased number of stroma and glands, increasing depth of the spiral arteries that supply the endometrium)
Create an environment that is friendly and helpful to possible incoming sperm (creation of channels within the cervix, allowing for sperm entry)
develop a primordial follicle (a primordial follicle matures into the Graafian follicle that is ready for ovulation)

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14
Q

Follicular phase

GnRH

A

Gonadotropin-releasing hormone(GnRH) is released from thehypothalamus→ stimulates the release ofFSH from the anterior pituitary → stimulates the primary follicles of the ovary to begin developing

Maturing primary follicles produce:
Inhibin A→ inhibits the release of FSH from the anterior pituitary (negative feedback)
Estradiol →stimulates development of a dominant follicle → the follicle secretesestradioluntil just before the LH surge

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15
Q

Follicular phase

Primary and dominant follicles

A

Primary ovarian folliclesdevelop due to ↑ FSH

Dominant follicle (Graafian follicle)continues to develop and secrete estradiol

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16
Q

follicular phase

LH surge

A

Estradiol levels will peak and ~12 hours later, the anterior pituitary releases aluteinizing “surge”→ triggers ovulation

During ovulation, a mature oocyte is released from the dominant follicle

The LH surge ends the follicular phase

17
Q

Luteal phase

general

A

Represents the time after ovulation when the ovary produces hormones to support a potential pregnancy and maintain a healthy endometrium
Occurs within the ovaries

Coincides with the secretory phase of the endometrium
Takes place typically during days15-28of the menstrual cycle

Under the control ofprogesterone

18
Q

luteal phase

corpus luteum and potential of this phase

A

The corpus luteum of the mature oocyte producesprogesterone
Progesterone feedback inhibits LH secretion from the anterior pituitary

If conception does not occur, LH levels continue to ↓ and thecorpus luteum recedes into acorpus albicans

Ifpregnancyoccurs, the secretion of human chorionic gonadotropin (hCG) saves the corpus
luteum and allows it to continue to secrete progesterone

Oocyte migrates to the fimbria of theFallopian tube

Potential offertilizationby sperm at this phase

19
Q

Endometrial Cycle

phases

A

There are 3 phases of the endometrial (uterine) cycle:
Desquamation or menses
Proliferative phase
Secretory phase

20
Q

Menses

general

A

Day 1 ofmenstrual bleeding marks the beginning of the next cycle
Coincides with day 1 of the follicular phase

If conception does not occur, the corpus luteum degenerates and progesterone levels decrease → causes desquamation of the functional layer of the endometrium(menses)

Endometrium dies secondary to apoptosis
Uterine contractions shed and expel the endometrium

The oocyte is lost in menstrual bleeding

Duration of menses is variable
2 and 7 days, but is usually around 5 days

Blood lost is primarily arterial

21
Q

Proliferative & Secretory Phase

A

Proliferative phase
Days 4–14 → creation of a new endometrium for the new cycle

Secretory phase
Day 15of the menstrual cycle
Preparation for potential oocyteimplantation
Triggered by estradiol and progesterone release
Ovulation is dependent on theLH surge

If pregnancy does not occur, progesterone levels decrease → inducing apoptosis of the functional layer of the endometrium, leading to menses

22
Q

Normal menstrual cycle

S/Sx

A

Sign
Vaginal bleeding
Acne

Symptoms
Bloating
Abdominal or pelvic cramping
Lower back pain
Breast tenderness
Mood swings/irritability
Headache
Fatigue

23
Q

Abnormalities of the Menstrual Cycle

Amenorrhea/ Menorrhagia /Metrorrhagia

A

Amenorrhea
Absence of menses due to hypothalamic, pituitary, ovarian, uterine, or vaginal causes
Can be primary (absence of menarche by the age of 15) or secondary (absence of menses for more than 3 cycles or 6 months in individuals with previously normal cycles)

Menorrhagia
Regular menstrual intervals with an excessive menstrualflow(> 80 ml for > 7 days)

Metrorrhagia
Irregular uterine bleeding in between menstrual periods or at irregular intervals

24
Q

Abnormalities of the Menstrual Cycle

Menometrorrhagia/ Dysmenorrhea/
Oligomenorrhea/ Polymenorrhea

A

Menometrorrhagia
Combination of menorrhagia (heavy menstrualflow(> 80 mL for > 7 days) and metrorrhagia (menses at irregular intervals)

Dysmenorrhea
Recurrent abdominalpainassociated with menstruation

Oligomenorrhea
Menstrual interval > 35 days

Polymenorrhea
Menstrual interval < 21 days

25
Q
A
26
Q
A