Reproduction II Flashcards
what are the functions of the female reproductive system?
- produce ova (eggs)
- receive sperm, facilitate fertilization
- house and nourish developing embryo, gives birth
- lactate, feed young
describe the anatomy of the female reproductive system
- ovaries: female gonad
- endocrine gland
- located in abdominal cavity
- held in place by several ligaments
what does the female reproductive system produce?
- gametes via oogenesis
- sex hormones - estradiol, progesterone
what are within the ovaries?
- follicles - where egg will mature and be released
- oocytes - cell that undergoes meiosis to produce eggs
oviducts (fallopian tubes)
- extend from uterus to each ovary, partially surround
- site of fertilization
- collects 2° oocyte from ovary, brings it to the uterus
- move oocytes via beating cilia, contractions
uterus
- pear-shaped, ~ size of fist
- site of embryonic development (expands during pregnancy)
- 2 layers:
(1) myometrium: thick wall of smooth muscle
(2) endometerium: lines lumen
endometrium
- lines lumen - connective tissue, glands, blood vessels
- thickens each month - prepare for pregnancy
- fertilization -> embryo implants
- no fertilization -> sloughed off -> menstruation
cervix
- lower part of uterus
- closes uterus, separates from vagina
- common site of cancer
- > 90% cases due to HIV
vagina
- elastic muscular tube
- extends to outside of body
- receives penis and sperm
- birth canal
name the parts to the vulva
- external genitalia
- labia majora
- labia minora
- clitoris - homologous with glans penis
- prepuce (clitoral hood) - homologous with foreskin
- urethra
- vaginal opening
what is oogenesis?
development of mature eggs
SEQ oogenesis prior to puberty
primordial germ cells (2n) -> mitosis -> oogonia (2n) -> mitosis -> 1° oocyte (2n)
1° oocytes
- begin meiosis, but stop in Prophase I
- arrested in Prophase I
- at birth, ~ 1-2 million 1° oocytes
- ~ 200k by sexual maturity
- each 1° oocyte within a follicle
- all are dormant until puberty -> a few mature each month
oogenesis starting at puberty
-each moth, 6-12 follicles mature within ovaries -> 1° oocyte grows, follicle cells around it proliferate (but only one will mature)
follicle cells
protective barrier
zona pellucide
thick glycoprotein layer between follicle cells and oocyte
what happens just before ovulation (each month)?
8-10 hours before release from follicle, 1° oocyte completes meiosis I, producing a polar body (n) and a 2° oocyte (n), which starts meiosis II but arrests at metaphase II
what happens in ovulation?
- as 2° oocyte matures, it moves to surface of ovary
- follicle cells secrete fluid, estrogens, enzymes -> break down ovary wall
ovulation
2° oocyte ejected from ovary in oviduct
Corpus Luteum
- “yellow body”
- portion of follicle left in ovary after ovulation
- develops into temporary endocrine gland (more later)
- secretes: estrogens and Progesterone (1000x more than estrogens)
what happens if sperm enters into the Corpus Luteum
- 2° oocyte completes meiosis II -> becomes a mature egg containing sperm nucleus
- oogenesis is complete!
what happens if no sperm enters into the Corpus Luteum?
- 2° oocyte disintegrates
- Corpus Luteum dies
- endometrium shed - Menstruation
- new follicle next cycle
menstrual cycle
- all mammals - endometrium thickens before ovulation
- only some have menstrual cycles
- estrous cycle
- menstrous cycle
estrous cycle
fertile, sexually receptive (“in heat”) only at certain times of year - most mammals
menstrous cycle
fertile intermittently, on a cyclic basis
what are the components to the menstrual cycle
- cyclic process of gamete maturation AND uterine lining development - prepares female body for pregnancy
- repeats every ~ 28 days unless fertilization and implantation occur
what are the two concurrent cycles to the menstrual cycle
ovarian cycle and uterine cycle
ovarian cycle
- follicular phase - follicle/oocyte maturation
- ovulation ~ Day 14
- Lutuel Phase - after ovulation, hormones from Corpus Luteum
uterine cycle
- menstrual flow phase - Days 1-5
- Proliferative Phase - endometrium starts again, before ovulation
- secretory phase - endometrium thickens, after ovulation
estrogen
principle female sex hormone
what is the main form of estrogen?
estradiol
- secreted by follicle cells, then by corpus luteum
- at puberty, stimulates growth of
(1) 1° sex characteristics
(2) 2° sex characteristics - stimulates monthly ovulation and endometrium thickening
what is the difference between 1° and 2° sex characteristics?
1° - sex organs
2° - breast development, broadening of pelvis, fat and muscle distribution
progesterone
- secreted mainly by corpus luteum
- completes preparation of endometrium for pregnancy, maintains it
- stimulates endometrial glands to secrete nutrient-rich fluid
SEQ the General Hormone Cascade
Hypothalamus -> GnRH -> AP -> FSH, LH -> Ovaries -> Estradiol and Progesterone
what are the different female sex hormones?
estrogen, estradiol and progesterone
what are the 3 different phases of the ovarian cycle, and how long does each last?
- follicular phase (Days 1-13)
- ovulation (Day 14)
- luteal phase (Days 15-28)
follicular phase
- FSH and LH stimulate follicle growth in ovaries
- as follicle grows, it releases more and more estradiol
what happens when follicle cells produce estradiol?
- slow rise during follicular phase
- low estradiol levels inhibit FSH and LH secretion by AP
SEQ Follicular phase - regulation (inhibition)
hypothalamus -> GnRH -> AP -> LH and FSH -> early follicle -> (inhibition) AP
SEQ Follicular phase - regulation (stimulation)
hypothalamus -> GnRH -> AP -> LH and FSH -> early follicle -> follicle matures -> late follicle -> (stimulation) high estradiol -> hypothalamus
what happens when there are low levels of estradiol?
negative feedback on AP
what happens when there are high levels of estradiol?
positive feedback on hypothalamus
maturing follicle
- enlarges and move to ovary surface
- ovulation ~ 1 day after LH surge
- 2° oocyte released into oviduct
- ovulation is due to positive feedback regulation
ovulation - regulation
- high levels of estradiol from mature follicle
- Positive feedback on hypothalamus
- high GnRH stimulates AP
- LH surge -> ovulation
- 2° oocyte to oviduct
luteal phase
-LH stimulates remaining follicle tissues -> corpus luteum -> secretes progesterone and estradiol -> (inhibit) hypothalamus
what is the effect of the inhibition that occurs in the luteal phase?
low GnRH and low LH and FSH
what is the effect of estradiol and progesterone from corpus luteum?
negative feedback on hypothalamus
what happens if there is no pregnancy in ovarian cycle?
- low FSH and LH cause corpus luteum to disintegrate
- low [estradiol] and [progesterone]
- hypothalamus secretes GnRH -> AP produces FSH -> stimulates next ovarian cycle
what happens if there is pregnancy in ovarian cycle?
- placenta releases human chorionic gonadotropin (hCG), which maintains the corpus luteum
- [estradiol] and [progesterone] remain high -> hypothalamus does NOT secrete GnRH -> AP does NOT produce FSH or LH -> no new ovarian cycle
what are the three phases of uterine cycle, and how long does each last?
- menstrual flow phase (Days 1-5)
- proliferative phase (Days 6-13) - before ovulation
- secretory phase (Days 15-28) - after ovulation
proliferative phase
- coordinated with follicular phase of ovarian cycle
- ovarian hormones stimulate uterus to prepare, support embryo
- growing follicle -> estradiol -> endometrium thickens
secretory phase
- coordinated with luteal phase of ovarian cycle
- corpus luteum secretes estradiol and progesterone -> endometrium development
endometrium development
- arteries enlarge
- endometrial glands grow
- secrete nutrient fluid -> sustain early embryo before implant
what happens if there’s no pregnancy in the uterine cycle?
- corpus luteum disintegrates
- low [estradiol] and [progesterone] -> arteries in endometrial lining constrict
- loss of circulation
- lining disintegrates
menstrual flow phase
- endometrial tissue, fluid, blood is shed
- new follicle begin to grow
- Day 1 of menstrual flow -> beginning of new ovarian/uterine cycles
