female reproductive biology Flashcards
ovarian follicles
stat as primordial follicles
grow into preantral follicle
astral (secondary) follicle
oestrogen’s produced in
granuloma cells (also corpus luteum)
require aromatase activity
regulated by LH and FSH
progesterone produced in
corpus luteum - thing formed after ovulation, everything left minus the ovum (tiny amount from follicular theca cells)
progesterone production regulated by
LH (via cAMP)
corpus luteum
the thing left behind after ovulation
the follicle minus the egg
granuloma cells can’t
form androgens from progesterone
theca cells can’t
produce oestrogen from androgens because they don’t have aromatase
oestrogen production is regulated by
LH and FSH
2 types of oestrogen receptors
Era and ERb
effects of oestrogen’s
facilitate growth of ovarian follicles and uterine tube motility
cyclical changes in the endometrium
increases flood flow and contractility of the myometrium
oestrogen dominated uterus is more sensitive to oxytocin
increases breast duct growth
progesterone is stimulated by
LH
progesterone binds
PRa, PRb which form transcription factors
mifepristone
blocks progesterone binding - morning after pill
GnRH
secreted in episodic bursts
oestrogen increases cycling prequency
progesterone decreases frequency
flliculogenesis
takes 1 year (so includes 11 other cycles)
phases of menstrual cycle
follicular, ovulation, luteal, pregnancy or regression
primordial follicles contain
immature ovum
follicular phase
several follicles enlarge, cavity forms around the ovum (antrum), filled with follicular fluid
10-15 days before ovulation - dominant follicle starts to grow rapidly, other regress (apoptosis)
oestrogen is now produced from ovary granulose cells (via theca cells)
oocyte increases zona pellucid (glycoprotein shell)
atretic follicles
not dominant ones -apoptose
ovulation
day of ovulation - distended follicle ruptures, ovum extruded into abdominal cavity
ovum picked up by oviducts and transported to uterus
oogenesis
all oocytes made by the 7th month
begin moeiss around birth but arrest at prophase (1° oocyte)
begin ovulation at puberty - 1° oocytes reenter ovulation
completes meiosis 1 to become a 2° oocyte and begins meiosis 2 and arrests at metaphase
granulose cells produce AMH which kills off all the other cells
if ovum is fertilised
meiosis 2 completed (now an ovum)
atresia
dying cells before they can produce functional ova
luteal phase
formation of a corpus luteum
after ovulation, ruptured follicle fills with blood to form a corpus haemoragicum
granulosa/theca cells proliferate and form lipid filled corpus luteum
secretes progesterone and oestrogen
becomes vasculogenic and grows until it dies
replaced by scar tissue and becomes corpus albicans
during the first 14 days
granolulossa cells producing lots of oestrogen which creates positive feedback to LH which triggers ovulation
LH surge
triggers ovulation
Lh and FSH causes rapid swelling of the follicle
moeisis reinitiated
- theca cells release proteolytic enzymes (coollagenase) which dissolves follicular capsule wall and causes degeneration of preovulatory opening
- prostaglandins trigger follicolare tissue to create smooth muscle contraction of the follicle and cause ovum expulsion
oestrogen causing LH surge
moderate constant oestrogen - surpasses GnRH and LH
aberrantly elevated oestrogen’s - increase GnRH and LH
LH surge
GnRH release rises throughout follicular phase
early follicular phase
myometrium
outer muscle wall
endometrium
inner lining
rich blood supply , highly glandular
undergoes cyclical growth, loss and repair - menstraul cycle
influences by cyclic changes in oestrogen and progesterone
the uterine cycle
proliferative - rapid endometrial thickening, proliferation of blood vessels and endometrial cells
secretory - CL develops corresponds to the luteal phase of the ovarian cycle and endometrial glands secrete fluids, becomes oedematous prpares uterus for implantation
menstrual - CL regresses, sudden drop n oestrogen and progesterone levels, endometrium thins and degenerates
corpus luteum regression
drives the next cycle
once luteolysis begins, FSH and LH levels re set, a new crop of follicles develop
eggs live for
12-24 hours after ovulation, so conception only occurs during this short window
fertilisation occurs in the Fallopian tube
steps of sperm meeting the ovum
- chemoattraction
- adherence to zona pellucide ZP3 receptors
- penetration and acrosome reaction
- adherence to cell membrane, digestion (cortical reaction) fusion
cortical reaction - serine proteases destroy ZP3 receptors to prevent polyspermy
endocrine changes in implantation
corpus luteum fails to regress - enlarges - secretes oestrogen, progesterone, relaxin, (inhibits myometrial contraction)
implanting syncytiotrophoblasts from placenta
human chorionic gonadotrophin
maintains corpus luteum of pregnancy
stimulates secretion of testosterone by the developing testes in XY embryos
