The Menstual Cycle

The average menstrual cycle lasts 28 days, with ovulation typically occurring around

day 14

The first menstrual cycle is termed

menarche.

. However, if an individual does not experience menarche before age 16, she is said to have

primary amenorrhea.

Primary amenorrhea may be caused by congenital abnormalities or congenital obstructions, such as an

imperforate hymen- hymen with no opening

what is Secondary amenorrhea

the cessation of menstruation characteristically diagnosed in the postmenarchal woman who has had 3 to 6 months without a menstrual cycle; may be associated with endocrinologic abnormalities or pregnancy.

what is the hypothalamic–pituitary–gonadal axis

complex interactions that take place between the hypothalamus, pituitary gland, and ovaries as part of the female reproductive cycle.

where and what is the purpose of the hypothalamus

the area within the brain that is located just beneath the thalamus and controls the release of hormones by the anterior pituitary gland

what is the anterior pituitary gland

the anterior segment of the pituitary gland, which is responsible for releasing follicle-stimulating hormone and luteinizing hormone during the menstrual cycle

The hypothalamus releases Gonadotropin-Releasing Hormone GnRH, which, in turn, stimulates the

release of hormones by the anterior pituitary gland.

the anterior lobe of the pituitary gland is responsible for the release of two chief hormones that influence the menstrual cycle:

follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

what is follicle-stimulating-hormone (FSH)

the hormone of the anterior pituitary gland that causes the development of multiple follicles on the ovaries

What is luteinizing-hormone (LH)

the hormone of the anterior pituitary gland that surges around day 14 of the menstrual cycle, resulting in ovulation

The ovary produces two hormones during the menstrual cycle,

estrogen and progesterone

What is estrogen

the hormone released by the ovary during the proliferative phase that initiates the proliferation and thickening of the endometrium

what are other functions of estrogen

regeneration of the endometrium after menses and the induction of salt and water retention. It also stimulates contractile motions within the uterine myometrium and the fallopian tubes.

what is progesterone

a hormone that prepares the uterus for pregnancy, maintains pregnancy, and promotes development of the mammary glands; primarily produced by the ovary and placenta

During the second half of the menstrual cycle, following ovulation, progesterone is produced by the

corpus luteum of the ovary

The hypothalamus releases GnRH, which influences the

anterior pituitary gland.

The anterior pituitary gland produces FSH and LH, which influence the

ovary

The ovary produces estrogen and progesterone, which influence the

endometrium

The ovarian cycle consists of two phases:

follicular phase and the luteal phase

The follicular phase of the ovarian cycle is considered to begin on and lasts up to?

day 1 and lasts until day 14; ending with ovulation

During the follicular phase, the anterior pituitary gland secretes FSH, which initiates the

follicular development of the ovary

during this phase, only one follicle will progress from

primordial follicle to primary follicle and then to become a secondary follicle; eventually maturing to become the Graafian follicle or dominant follicle before ovulation

This Graafian follicle contains the developing oocyte (egg) within a region called the

cumulus oophorus

Around day 14, LH, produced by the anterior pituitary gland, stimulates ovulation, at which time the Graafian follicle ruptures and expels a small amount of fluid and the ovum into the peritoneum. At the time of ovulation, the individual may feel a twinge of pain, and this is termed

mittelschmerz

The ovum that was expelled by the ovary is picked up by the

fimbria of the fallopian tube and is propelled through the tube

The second phase of the ovarian cycle, days 15 to 28, is termed the luteal phase. After the Graafian follicle ruptures, bleeding occurs into that space, resulting in the

corpus hemorrhagicum. That structure then rapidly converts into a temporarily endocrine gland in the form of the corpus luteum

what is the corpus luteum

literally interpreted “yellow body,” primarily produces progesterone to maintain the thickness of the endometrium and prepares the endometrium for the (conceivably) fertilized ovum. All the other follicles undergo atresia.

Remember this chain of events

primordial follicle > primary follicle > secondary follicle > Graafian (dominant) follicle > ovulation > corpus hemorrhagicum > corpus luteum > corpus albicans

While the corpus luteum depends on LH to be maintained, progesterone negatively inhibits the production of LH by the anterior pituitary gland, resulting

regression of the corpus luteum.

The remaining structure of the corpus luteum is now termed the

corpus albicans, which can often be seen sonographically as a small echogenic scar on the ovary.

. For example, during the early follicular phase and late luteal phase, the ovarian artery will demonstrate a

high-resistive pattern, with increased impedance, and absent or low end-diastolic velocity.

During the late follicular and early luteal phases, the ovary will demonstrate a

low-resistive pattern, with low impedance and higher levels of diastolic flow.

what is the innermost portion of the endometrium

functional layer (stratum functionale), is the layer that is stimulated by the hormones of the ovary to undergo changes throughout the menstrual cycle; also provides an appropriate location for the implantation of the products of conception

The outermost portion of the endometrium is

basal layer (stratum basale), is only slightly altered during the menstrual cycle. It consists of dense, cellular stroma.

The endometrial cycle consists of two phases:

proliferative phase and the secretory phase.

when does the proliferation phase occur

During the first half of the menstrual cycle

the proliferation of the endometrium, which is described as the multiplication of similar forms, occurs during the

proliferative phase of the endometrial cycle because the functional layer increases in thickness

The proliferative phase may be divided into two phases

early and late, with the late proliferative phase often being referred to as the periovulatory phase; which occurs around the time of ovulation

The secretory phase of the endometrial cycle occurs

after ovulation and is stimulated by progesterone. Progesterone maintains the thickness of the endometrium in preparation for implantation.

Should fertilization not take place,

menses begin on day 1 of the cycle, resulting from a lack of estrogen and progesterone.

Conversely, if fertilization does occur, the endometrial thickness is maintained by the continual production of progesterone by the

corpus luteum of pregnancy

days 1 through 5 of the menstrual cycle correlate with

menses, when endometrium is shedd

Following menses, the ovary is in the

follicular phase, whereas the endometrium is in the proliferative phase

Following ovulation, the ovary begins the

luteal phase, whereas the endometrium enters the secretory phase

“Ovaries Freely Let Every Period Start”

Ovary

Follicular

Luteal

Endometrium

Proliferative

Secretory

Days 1–14

ovary in follicular phase

endometrium is proliferative phase

Days 15–28

Ovary in luteal phase

endometrium in secretory

. During menses, the endometrium typically appears as

thin, echogenic line (4mm)

During the early proliferative phase, the

the functional layer gradually increases in size and becomes more hypoechoic (4 and 8 mm)

During the late proliferative phase or periovulatory phase, which is between days 5 and 14, the endometrial layers

display a stark contrast (6 and 10 mm)

In the periovulatory phase,

three-line sign-the outer echogenic basal layer surrounds the more hypoechoic functional layer, with the functional layer separated by the echogenic endometrial stripe

Following ovulation,

the secretory endometrium is maintained by the production of progesterone because the endometrium becomes thickened and echogenic in appearance (7 and 14 mm)

Fertilization, or conception, typically occurs on

day 15 with the union of the egg and sperm in the fallopian tube.

The cells that surround the blastocyst, the syncytiotrophoblastic cells (trophoblastic cells), then begin to produce

human chorionic gonadotropin (hCG); maintaining the corpus luteum to produce estrogen and progesterone, which, in turn, maintains the thickness of the endometrium so that implantation can take place and the pregnancy can continue to progress normally

Dysfunctional uterine bleeding (DUB) is abnormal vaginal bleeding that occurs outside of a regular menstrual cycle, usually caused by hormonal imbalances rather than structural uterine issues and

may be idiopathic or possibly related to hormonal imbalances, resulting in endometrial changes with subsequent irregular bleeding. IE, polycystic ovary syndrome which causes anuovulation

Abnormal uterine bleeding (AUB) is a

difference in frequency, duration, and amount of menstrual bleeding, and it may be caused by a number of complications

One of the more common suspicious pathologies that results in AUB is the presence of

fibroid tumors or leiomyomas within or abutting the uterine cavity

another etiology of AUB and painful menstruation

Adenomyosis, which is ectopic endometrial tissue within the myometrium of the uterus

In perimenopausal or postmenopausal population, AUB origins are

endometrial hyperplasia, endometrial polyps, and endometrial carcinoma,

Causes of Abnormal Uterine Bleeding Can Be Structural or Nonstructural

Uterine fibroids (leiomyoma)

Adenomyosis

Cervical polyps

Endometrial polyps

Endometrial hyperplasia

Endometrial cancer

Hypothyroidism

Anovulation

Iatrogenic

Ovulatory dysfunction

Coagulopathy

Abnormal Uterine Bleeding Term

Amenorrhea- Absence of menstruation; can be classified as either primary amenorrhea or secondary amenorrhea

Cryptomenorrhea - Monthly symptoms of menstruation without bleeding

Dysmenorrhea

Menorrhagia (hypermenorrhea) - Abnormally heavy and prolonged menstruation

Metrorrhagia (intermenstrual bleeding) - Irregular menstrual bleeding between periods

Menometrorrhagia- Excessive or prolonged bleeding at irregular intervals

Oligomenorrhea - Irregular cycles >35 days apart

Polymenorrhea- Frequent regular cycles but <21 days apart

Hypomenorrhea - Regularly timed menses but light flow