Physiology of Menstruation

Menstrual Cycle

can be defined as episodic uterine bleeding in response to cyclic hormonal changes.

Menstrual Cycle

the process that allows for conception and implantation of a fertilized ovum

Menstrual Cycle

can be defined as episodic uterine bleeding in response to cyclic hormonal changes.

Menstrual Cycle

the process that allows for conception and implantation of a fertilized ovum

Menstrual Cycle

brings an ovum to maturity and renew a uterine tissue bed that will be responsible for its growth should it be fertilized

9-17 years old

Beginning of a Normal Menstrual Cycle

average = 28 days; cycle ranges = 23-35 days

Beginning of a Normal Menstrual Cycle

Average flow = 2-7 days; ranges = 1-9 days

Duration of menstrual flow

average 30-80 ml per menstrual period

Amount of menstrual flow

dark red; a combination of blood, mucus, and endometrial cells

Color of menstrual blood

Hypothalamus

is a structure deep within the brain that keeps the body in a state of balance among the body systems needed for the body to survive and function correctly

Hypothalamus

produces hormones that play a crucial role in the body functions

Gonadotropin-releasing hormone (GnRH)

a hormone that the hypothalamus produces that is involved in the regulation of the menstrual cycle

Gonadotropin-releasing hormone (GnRH)

is secreted in a cyclic or pulsatile manner, hence the cyclic pattern also of menstruation

Gonadotropin-releasing hormone (GnRH)

is mainly produced to stimulate the pituitary gland to begin producing the gonadotropic hormones

Diseases

____ of the hypothalamus that cause a deficiency in the release of this hormone can result in delayed puberty

early activation

Disease causing ___ ___ or release of this hormone can lead to abnormally early sexual development or precocious puberty

• FSH (follicle-stimulating hormone)

• LH (luteinizing hormone)

two hormones that the anterior lobe of the pituitary gland (adenohypophysis) produce

FSH (follicle-stimulating hormone)

a hormone that is active early in the cycle and is responsible for the maturation of the ovum

LH (luteinizing hormone)

a hormone that becomes most active at the midpoint of the cycle

LH (luteinizing hormone)

is responsible for the release of a mature egg cell from the ovary (ovulation) and growth of the uterine lining during the second half of the menstrual cycle

• Proliferative phase

• Secretory phase

• Ischemic phase

Three phases of the menstrual cycle

First phase (proliferative phase)

occurs immediately after a menstrual flow (usually occurs during the first 4-5 days of a cycle.

endometrium

At the first phase, the ____ is very thin. As the ovary begins to produce estrogen, the ____ begins to proliferate. This growth is very rapid and increases the thickness of the ___ approximately eightfold. This increase continues for the first half of the menstrual cycle.

Second phase (secretory phase)

occurs after ovulation, when the formation of the progesterone in the corpus luteum causes the glands of the uterine endometrium to become twisted in appearance and dilated with high quantities of glycogen (a simple sugar) and mucin (a protein)

increase

During the second phase, the capillaries of the endometrium ___ in amount until the lining becomes a rich, spongy, velvet-like layer.

Third phase (ischemic phase)

occurs if fertilization does not occur and the corpus luteum in the ovary begins to regress after 8-10 days.

progesterone, estrogen, endometrium

During the third phase, as the ovary regresses, the production of ___ and ___ decreases. With the withdrawal of progesterone stimulation, the ___ of the uterus begins to degenerate (at approximately day 24 or day 25 of the cycle). The capillaries rupture, with minute hemorrhages, and the endometrium sloughs off.

Menses

the endpoint of a menstrual cycle

First day of menstrual flow

used to mark the beginning of a new menstrual cycle

30 to 80 ml blood

The menstrual flow or menses contains approximately ___ __ ___ __ ____ from the ruptured capillaries, mucin from the glands, fragments of endometrial tissue and the microscopic, atrophied and unfertilized ovum.

iron loss

The __ ___ in a typical menstrual flow is approximately 11 mg. This is enough loss that many women need to take a daily iron supplement to prevent iron depletion during their menstruating years.