Unit 3: Menstruation Flashcards
Ovaries after ovulation:
•ovulation = release of the egg from the follicle when it is mature (day 14 of menstrual cycle).
•egg enters the fallopian tube.
•corpus luteum = empty follicle after ovulation.
•yellow colour.
•induced by lutenizing hormone (LH) to produce progesterone for 10 days after ovulation.
•if no fertilization occurs after 10 days, corpus luteum breaks down and progesterone levels drop—> causes the endometrium to shed (menstruation).
•corpus albicans = scar remaining when corpus luteum degenerates.
Hormonal control of reproductive system:
-hypothalamus—> GnRH—> anterior pituitary gland—> FSH and LH.
- FSH = follicle stimulating hormone:
•causes maturation of the follicle with the egg.
•stimulates the secretion of estrogen from the egg.
•if too much estrogen, it feeds back on the pituitary and inhibits the secretion of more FSH.
- LH = lutenizing hormone:
•stimulates the formulation and development of the corpus luteum.
•therefore leading to the secretion of progesterone.
Becoming a woman (before birth):
•sex chromosomes:
-XX; ovaries descend to pelvic brim.
Becoming a woman (puberty):
•around 9-13 years.
•estrogen causes:
-final growth of primary sex organs.
-secondary sex characteristics.
-follicle development (ovum) each month.
Secondary sex characteristics:
•develop as a result of hormonal stimulation.
•characteristics include:
-enlarged breasts.
-hair growth.
-wider at hips than at shoulders.
-fat deposits around buttocks and hips.
-more fat than men.
-hands and feet are usually smaller and narrower than males.
Menstrual cycle:
•typically 28 days.
•really 2 cycles:
1. Ovulation cycle (egg release).
2. Uterine cycle (endometrium thickening and shedding).
Menstrual cycle: 4 phases:
•menstrual cycle consists of 4 phases:
1. Menstrual phase/flow phase (days 1-5).
2. Follicular phase/proliferative phase (days 6-14).
3. Ovulatory phase (day 14).
4. Luteal phase/secretory phase (days 15-28).
Menstruation:
-monthly discharge of blood and fluid from the uterus.
Menstruation (Flow phase (day 1-5)):
•all hormone levels low causing endometrium to be shed—> bleeding (20-80 mL for 2-8 days).
•low hormone levels responsible for:
-headaches, cramps, bloating, nausea, mood changes.
Menstruation (follicular phase (day 6-13)):
•increase in FSH levels.
•new follicle matures.
•follicle cells secrete estrogen:
-endometrium thickens with blood and fluids.
-estrogen triggers a release of LH.
•increase in FSH stimulates the follicles within the ovary to grow.
•growing follicle secretes estrogen in increasing amounts.
•when estrogen levels are high enough, estrogen signals to anterior pituitary (in brain) to turn off FSH secretion (negative feedback).
•increase in estrogen also stimulates LH release from anterior pituitary (positive feedback: more estrogen = more LH).
•hormonal increases cause endometrial lining to develop and thicken.
Menstruation (ovulation phase (day 14ish)):
•increasing estrogen from follicle causes surge of LH called “the LH surge”.
•LH surge causes ovulation—> release of secondary oocyte from ovary.
•empty follicle is now called corpus luteum (CL).
-high LH causes ovulation.
-fertile for about 24 hours.
Menstruation (luteal phase (day 15-28)):
•LH causes remaining follicle cells to form the corpus luteum.
•corpus luteum:
-yellowish endocrine gland.
-secretes progesterone and estrogen.
-thickens/maintains uterine lining.
•progesterone inhibits further ovulation (birth control pills).
•LH stimulates corpus luteum to secrete progesterone and estrogen.
Progesterone:
•prevents further ovulation.
•prevents uterine contractions.
•promotes thickening and maintenance of endometrium.
•firms cervix to prevent expulsion of fetus.
-progesterone & estrogen turn off LH and FSH release (negative feedback).
-endometrial glands begin receiving nutrients to prepare for embryo.
If fertilization occurs:
•the embryo produces HCG which causes the corpus luteum to continue progesterone production past the 10 regular days until the placenta is big enough and ready to take over.
•HCG is the hormone that is present in urine when females take home pregnancy tests.
If no fertilization occurs:
•CL degenerates—> causes decreased levels of progesterone and estrogen—> low levels of LH and FSH—> stimulates uterine connections—> endometrial lining sheds—> menstrual phase begins again.
Menopause:
•around 50 years no more follicles develop.
•decline in estrogen and progesterone.
-hot flashes, increased risk of heart disease, increased risk of breast and uterine cancers, decreased bone mass.
•hormone replacement therapy: can relieve menopause symptoms.
•risks include:
-blood clots, heart disease, increased breast and colorectal cancer risk.
