Module 2_PART 3

Menstrual Cycle (Female Reproductive Cycle)

Episodic uterine bleeding occurring in response to cyclic hormonal changes to mature an ovum and renew the uterine tissue bed for implantation.

Menarche Timing and Health Teaching

The first menstrual period occurs at an average age of 12.4 years (normal range: 9 to 17 years), warranting health education as early as fourth grade.

Menstrual Cycle Length Characteristics

The average cycle length is 28 days (measured from the first day of one flow to the first day of the next), with typical ranges between 23 and 35 days.

Duration of Menstrual Flow

The average duration of menses is 4 to 6 days (normal range: 2 to 7 days; extended abnormal limits: 1 to 9 days).

Amount of Menstrual Flow

The average volume lost is 30 to 80 mL per cycle; saturating a pad or tampon in less than an hour indicates abnormally heavy bleeding.

Color and Odor of Menstrual Flow

Dark red in color, consisting of blood, mucus, and endometrial cells, with a normal odor similar to marigolds.

Four Organs of Menstrual Physiology

The hypothalamus, pituitary gland, ovaries, and uterus, all of which must function synchronously for a complete cycle.

Hypothalamic Role in Menstruation

Synthesizes and releases GnRH (LHRH) in a cyclic manner to stimulate pituitary secretion of FSH and LH; inhibited by high estrogen, progesterone, prolactin, FSH, or LH.

Pubertal Hypothalamic Desensitization

The transition at puberty where the hypothalamus becomes less sensitive to low estrogen feedback, allowing monthly cyclic GnRH secretion to begin.

Anterior Pituitary Role in Menstruation

Produces FSH early in the cycle to mature ovarian follicles and LH at midcycle to trigger ovulation and stimulate the corpus luteum.

Gonadotropic Hormones

Pituitary hormones (FSH and LH) named for their ability to stimulate growth and activity in the gonads (ovaries).

Follicular Fluid

A clear fluid produced by growing ovarian follicle cells under FSH stimulation, rich in estrogen (predominantly estradiol) with small amounts of progesterone.

Graafian Follicle Maturation

A mature ovarian follicle appearing as a fluid-filled blister measuring 0.25 to 0.5 inches across on the ovarian surface containing the haploid ovum.

Meiotic Reduction in Oogenesis

By 14 days before cycle completion, the ovum finishes meiotic division to reach 23 haploid chromosomes and mitotic division into a functional primary oocyte and non-functional secondary oocyte.

Ovulation

The release of a mature ovum from the ruptured graafian follicle triggered by an LH surge and prostaglandin release, occurring approximately 14 days before the next cycle starts.

Calculation of Ovulation Day

Calculated by subtracting 14 days from the total cycle length (e.g., day 6 in a 20-day cycle, day 14 in a 28-day cycle, day 30 in a 44-day cycle).

Corpus Luteum (Yellow Body)

The ovarian structure formed from the ruptured follicle under LH influence, secreting lutein (high in progesterone, with some estrogen).

Basal Body Temperature (BBT) Shift

Drops by 0.5° to 1° F just before ovulation due to low progesterone, then rises by 1° F the day after ovulation due to thermogenic progesterone, staying elevated until day 24.

True vs. False Corpus Luteum

Persists for 16 to 20 weeks if pregnancy occurs (true corpus luteum); regresses after 8 to 10 days if unfertilized (false corpus luteum).

Corpus Albicans (White Body)

The white, fibrous scar tissue left behind after the false corpus luteum atrophies in the absence of fertilization.

Four Phases of the Uterine Cycle

Proliferative (follicular) phase, Secretory (luteal) phase, Ischemic phase, and Menses (menstrual) phase.

Proliferative Phase (Estrogenic/Follicular/Postmenstrual)

Days 5 to 14; ovarian estrogen stimulates rapid endometrial proliferation, increasing uterine lining thickness eightfold from a thin single cell layer.

Secretory Phase (Progestational/Luteal/Premenstrual)

Days 14 to 24; progesterone from the corpus luteum causes endometrial glands to become dilated and corkscrew-shaped (storing glycogen and mucin) with rich, velvety capillary beds.

Ischemic Phase

Days 24 to 28; regression of the corpus luteum leads to estrogen and progesterone withdrawal, causing capillary rupture, minute hemorrhages, and endometrial degeneration.

Menses Phase (Menstrual Flow)

Days 1 to 5; the shedding of the uterine lining composed of blood from ruptured capillaries, glandular mucin, endometrial fragments, and the atrophied unfertilized ovum.

Cervical Mucus Characteristics Throughout Cycle

Thick and scant during early and late phases (sperm-hostile under low estrogen/high progesterone); thin, copious, and watery at ovulation (sperm-friendly under high estrogen).

Fern Test (Arborization)

The formation of a microscopic fernlike sodium chloride pattern on a dried cervical mucus slide under high pre-ovulatory estrogen; absent in the progesterone-dominant luteal phase.

Spinnbarkeit Test

The physical stretching of thin, watery cervical mucus into long elastic strands at peak estrogen levels just before ovulation.

Gonadotropin-Releasing Hormone (GnRH)

A hypothalamic hormone that acts on the anterior pituitary gland to stimulate the synthesis and release of FSH and LH.

Follicle-Stimulating Hormone (FSH)

An anterior pituitary hormone that stimulates primordial ovarian follicle growth and maturation of the ovum.

Luteinizing Hormone (LH)

An anterior pituitary hormone whose midcycle surge triggers ovulation, promotes corpus luteum formation, and regulates progesterone and estrogen synthesis.

Estrogen

An ovarian hormone produced by follicles and the corpus luteum that promotes endometrial proliferation and maintains female reproductive anatomy and secondary sex characteristics.

Progesterone

A hormone secreted by the corpus luteum, vital for conditioning and maintaining a thick, secretory endometrium for fertilized ovum implantation.