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The menstrual cycle
Jennifer Deveron 12 March 2015
Transcript of The menstrual cycle
Puberty “refers to the process of physical changes by which a child’s body becomes an adult body capable of reproduction”.
Transitional period between the juvenile state and adulthood
Hormones involved in regulating changes during puberty
establishing the ovarian cycle
Series of cyclic changes that the ovary & uterine endometrium undergoes each month in response to changing levels of hormones in the blood
Uterine changes coordinated with the phases of the
(main goal = release of egg, ovulation).
Occurs on a monthly basis (28 day cycle)…. range 20-40 days…On average, menses lasts ~5 days
Main goal of Uterine cycle = preparation for support of embryonic development & maintenance if pregnancy occurs!!!
Shedding of endometrial lining = menstruation
Occurs between puberty and the end of the reproductive years
Ovarian Cycle & Uterine cycle mirror one another
Both dependent upon interrelationships between the brain, pituitary gland, ovaries & uterus;
Totally controlled by hormones
Ovarian cycle: produce ovum;
Phases: Follicular, Luteal
Uterine cycle: Preparation of egg for fertilization, preparation for pregnancy, evaluation of pregnancy status; not pregnant = reabsorption and excretion, begin again…
Phases: Menstrual, Proliferative, Secretory
The menstrual cycle
Breast development and maintenance
Adding fat to breasts, hips, thighs during puberty
Improving bone strength and density
Accelerating bone maturation and bringing epiphyses to closure, completing growth
Growth of the uterus
Development of the endometrial lining to a thickness necessary to support pregnancy and menstruation
Thinning of cervical mucus at ovulation
Promoting and maintaining vaginal mucosal thickness and secretions
Serving as the primary feedback to the brain of sex hormone levels
Participating in triggering ovulation
Preservation of egg cells
Effect on lipids
Estradiol - A very busy hormone, responsible for many things:
Development of secondary sex characteristics:
Estrus V. Menstruation
Estrus cycles reabsorb
the endometrium if conception does not occur during that cycle.
Menstrual cycles shed
the endometrium through menstruation instead.
Species with estrus cycles, females are generally only sexually active during the estrus phase of their cycle (MATING restricted to ovulation period)
Females in estrus exhibit external signals
Females of species with menstrual cycles can be sexually active at any time in their cycle, even when they are not about to ovulate.
Humans do not have external signs to signal receptivity at ovulation
Hypothalamus - Pituitary interaction:
Hypothalamus integrates nervous systems & endocrine systems
Hypothalamus secretes GnRH to anterior pituitary in rhythmic, pulselike manner
GnRH stimulates anterior pituitary to release FSH & LH
Complex relationship based on both positive & negative feedback mechanisms
If LH or FSH pulses slow down follicles don't develop properly
Granulosa cells in ovary develop and begin secreting estrogen which particpates in feedback control of LH & FSH
Adult cyclic pattern achieved & hormonal interactions stabilize – events heralded by menarche (first menstrual period); Weight important factor for menarche.
from Doshi & Agarwal, 2013
Problems with the Menstrual Cycle:
PMS: Pre-menstrual Syndrome
a group of symptoms that start 7 to 14 days before menses
Physical fluctuations during cycle are normal.
WHY? Estradiol & Progesterone levels fluctuate dramatically (especially during the premenstrual phase)
PMS a misogynistic myth?
Is PMS a way of making women’s normal cycle dysfunctional? (labeled a psychological disorder in the DSM)
Are we just linking ailments to our reproductive organs in a way that makes women less equal to men?
– failure to menstruate by age 18
Prevalence = 1% of women in US
thyroid disorders, problems with adrenal cortex or pituitary gland
Genentics - Mayer-Rokitansky-Kuster-Hauser syndrome mullerian agenesis or dysgenesis; AIS; Turner’s syndrome - ovaries undergo atresia (absent/closed), no primordial oocytes
– uterine bleeding blocked due to imperforate hymen
– cessation of periods any time between menarche and menopause, associated with stress
Low body fat, low dietary fiber (impact estrogen)
Endorphins can inhibit GnRH
Abnormal uterine bleeding
Make sure that bleeding is coming from the vagina and is not from the rectum or in the urine. Inserting a tampon into the vagina will confirm the vagina, cervix, or uterus as the source of bleeding.
Careful history is important
See your gynecologist for a complete exam
– painful menses (without any evidence of physical abnormality)
Cramps – directly related to prostaglandins
(NSAIDS or PG inhibitors)
Ibuprofen, naproxin or asprin
Home remedies: Hot water bottle, heating pad, exercise, yoga, orgasm
Non-Western remedies: Accupuncture
Oral contraceptives (which reduce prostaglandin production)
- Physical abnormalities can result in painful periods:
Pelvic inflammatory disease & cervical stenosis
Fibroid tumors (increased flow, clotting, pain)
MYTHS about the Menstrual Cycle
No swimming, intercourse, making decisions during your period...
Some cultures very oppressive towards menstruating women.
LUNAR CYCLE: 29.5 days
Why did mestruation evolve?
Hidden ovulation side effect?