Gonadotropin Releasing Hormone
- Input into hypothalamus release GnRH
- Releasing hormone
- Made in nerve cells in hypothalamus called gonadotrophs
- Travels down axon of nerves + goes to portal system of anterior pituitary
o Endocrine cells in blood system (FSH + LH)
- FSH + LH reduce when fertilisation occurs  don't want another pregnancy
- Dead CL= aren’t releasing P
- Pulsation rate of GnRH= either LH or FSH released  cells secrete both of these
o Pulsation rate determines which to secrete
Primordial germ cell
- Primordial germ cells develop in utero at around 5wks
o Move to gonads
o 5-7mill made via mitotic divison
o Diploid stem cells
o Over time= dimish  atresia
o 7mths gestation= start to undergo meiosis differentiate into gametes
 Haploid= 23 chromosomes
o Foetal germ cells go into meiotic arrest
 Start meiosis but then stop in prophase I
 Resumption of meiosis occurs just before ovulation of particular egg
 B/c follicles too small + not creating right proteins for process to continue
 Creation of final haploid cell not until ovulation
Folliculogenesis
- Monthly cycle driven by whats occurring in ovaries rather than hormones
- FSH= Causes follicles in ovary to mature  follicularmaturation
o Causes maturity of whole follicle
o Growth of layers + thecal cells
- Primordial germ cell primary follicle (containing primary oocyte)  primary follicle (pre-antral=
space being made)  secondary follicle (zona pellucida) tertiary follicle
o Preantral phase
 Primary follicle made up of somatic cells + primary occyte
 Contains primary oocyte  juvenile gamete (incomplete meiosis)
 Primary oocyte protected by somatic cells
o Outer layer= basal lamina  epithelial tissue lies on
o Granulosa cells line inner lining  protect cell while waiting for ovulation +
meiosis to complete
o Avascular= blood cant get in
 Oocyte Inside germinal vesicle
 Primary follicle (pre-antral)
 Protective layer= zona pellucida
 Secondary follicle
 Still diploid
 FSH has receptors on granulosa cells= causing changes
 Tertiary follicle
 Thecal cells grow around zona pellucida= tertiary follicle formed
 Thecal cells respond to LH
 Receptor for LH
o LH attaches to thecal cells
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o Brings cholesterol into cell + causes enzyme upregulated in the cell=
androgens are made
o Androgens cross basal lamina + go into granulosa cell
 Androgen converted into oestrogen
 Still pre-antral phase
o Antral phase
 Antral follicle
 Antrals form= contrain water
o coalesce (all join up)= form antrum
 antrum divides granulosa cells
o 2 sections of granulosa cells
 Cumulus cells
 Mural granulosa
 Egg inside zona pellucida + cumulus cells
 Cumulus-oocyte complex= that's what gets ovulated out
Oestrogen rises= dip in FSH  made in tertiary follicle
o Rise in O mid cycle= causes positive feedback to cause LH surge
o LH causes P to be released from granulosa cells
o LH surge= ovulation
o When O been high for 50hrs (high b/c thecal cells + granulosa cells making O in tandem)=
surge of LH from anterior pituitary
LH= causes meiotic arrest to end  stimulates division until metaphase II
o Causes maturation of the gamete= gametogenesis
o On the way to making haploid cell
Follicles have 2 main functions
o Endocrine function
 Secrete O + P (steroid hormones)
 Steroidogenic function
 O+P help fertilised egg remain in uterus
o Gametogenic function  growth + maturation of sex cell
 Meiotic changes  diploid to haploid
Dominant follicle
- Briefly diminishing FSH levels before ovulation= causes dominant follicle  others die (atresia)
- As dominant follicle grows= O rises b/c more granulosa cells
Corpus Luteum
- Thecal cells remain= become thecal lutein cells
- P produced instead of O once oocyte released
- Angiogenesis= growth of blood vessels around CL brings in cholesterol= P production
o P levels rise dramatically
o O stops temporarily b/c enzyme (aromatase) stops working for a bit (responsible for androgen
to oestrogen conversion)
Ovulation
- At ovulation= fimbriae stroke ovarian wall
o Causes waves inside stroma of ovary + allow ovarian follicle to move to the edge of the ovarian
wall
o Mature follicle= 2cm big  can cause pain
o Inflammatory event
 Inflammatory mediators erode ovarian wall
 Point of erosion= stigma
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Cumulus-oocyte complex erupts from follicle  emitted as complex to maximise size for
fimbriae to sweep
- Surge in LH= change in mucus in cervical canal  watery + pH rises
o Allows for sperm to come through
o Acidic + thick would be barrier
- Time of conception
- After fertilisation occurs= cervical mucus becomes thick + acidic  prevent more sperm
entering/fertilising + stops infection
Fertilised egg
- Only move from metaphase II to completed meiosis if fertilised
- Fimbriae sweep into ampulla Smooth muscle peristalsis + Moist thin mucus
- At ampulla= slows down passage
o Cilia movement stop
o Tonic contraction
o Intense folding of epithelial layer
- Ampulla= where fertilisation occurs
- STI= scarring on ovaries  more likely to have embryo implanting in extrauterine region
- Fertilisation= resumption of mitosis  46 chromosomes
Sperm
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Flagella= motility
Genetic info in head
Tip of head cut off= attach to egg
Burrow through zona pellucida
When touches the zona pellucida= cortical reaction  stops anymore sperm from entering that egg
o Egg can only be fertilised by 1 sperm  maintain 46 chromosomes
Pre-embryonic phase
- Once fertilised= peristaltic contractions pick up again + so does cilia movement  aim for cell mass
to move into uterus
o Becomes zygote= divides into morula (compacted within ZP)  blastocyst by the time it
comes out into the uterus
o Enters uterus about 5-6 days after ovulation
- Cells all compacted within ZP in morula phase
- Blastocyst= ZP disintegrates
- Cells start to form on side to be implanted in uterine wall  inner cell mass= embryoblast
o Other side= trophoblast
- Trophoblast differentiates into diff types of cells
o Burrows into endometrium  immune response doesn't occur b/c P causes dampening of
maternal immunological function
o Syncitotrophoblast secretes hCG  rescue dying CL + make CL cont to produce P
 hCG looks very similar to LH  similar structure
 P important to maintain pregnancy
o Previous c-section= increased risk of placentation complications
Uterus
- O in follicular stage as dominant follicle getting ready to release
- Have to build up endometrium again after last bleed
- Strata basalis= basal layer
o Stratum functionalis= top layer  lost during menstruation= need to regain
 Contained spiral arteries
 After period each month= need to regrow 2/3 of endometrium
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 Grow via angiogenesis
P causes quiescence= no contractions of uterus when zygote trying to implant
O builds new layer in proliferative phase
After LH surge + rise in P= secretory phase