Initiation of pregnancy Flashcards
Name the parts of the uterine tube;
Isthmus
Ampulla
Infundibulum
Common site of fertilisation:
Ampullary-isthmic junction
Female fertility is
Episodic
Male fertility is
Continual
2 phases of the ovarian cycle:
Follicular
Luteal
Phases of the uterine cycle:
Menstration
Proliferation
Secretary
Match the ovarian cycle and uterine cycle phases
Follicular phase: menstration and proliferative
Luteal phase: secretory phase
Follicular phase ends at…
Ovulation (day 14)
Mentration begins at…
Start of cycle (14 days after ovulation)
Most fertile at what point in menstrual cycle?
5 days before and 1 day after ovulation
What is released from the hypothalamus?
GnRH
What is released from the anterior pituitary gland?
FSH LH
Follicular phase:
LH acts on theca cells to produce androgens
FSH acts on granulosa cells to produce aromatase, inhibin and ostrogen
Oestrogen has a -ve feedback on LH and inhibin has a -ve feedback on FSH
What causes the LH surge?
High levels of oestrogen, changes from -ve to +ve feedback
Events of the luteal phase:
Follicle becomes corpus luteum which produces progesterone and some oestrogen. This has a -ve feedback on LH
If no pregnancy occurs …
Corpus luteum becomes corpus albicans. Stops producing progesterone so endometrial lining is shed.
If pregnancy occurs …
hCG is produced which is structurally similar to LH. Maintains endometrium and CL
What produces progesterone at the start of pregnancy and what takes over?
Corpus luteum
Placenta
Average time sperm can survive:
5 days
Average survival of occyte
24 hrs
Sperm must undergo what to be able to fertilise the egg?
Capacitation
Capacitation involves:
- Acquiring characteristic ‘whiplash’ movement
- Acrosome reaction (shedding glycoprotein coat by rubbing on oviduct epithelia)
What is capacitation dependent on?
Calcium
2 enzymes in acrosome:
Hyaluronidase
Acrosin
Acrozene =
Digests zona pellucida
Hyaluronidase =
Digests hyaluronic acid made my cumulus cells
Acrosome reaction occurs in response to …
Oocyte being near
What does sperm bind to to fuse with oocyte?
ZP 2/3 (zona pellucida glycoproteins 2 and 3)
How does sperm activate the egg?
- Release phospholipase gamma C
- Ca2+ influx
- Breaks down MPF
- Resumes meiosis II
MPF =
cyclin B + cdk 1
Before activation, egg is arrested at
Meiosis II
How does an egg prevent polyspermia:
Cortical granules release contents, conformational change of Zp 2/3
2nd polar body is shed to form:
Female pronucleus
Multiple sperm bind =
Polyspermia
Meiotic error within egg, 2 female pronuclei =
Digynic
Artificial triggering of Ca2+ transcience causes resumption of meosis II without sperm =
Parthenogenetic
What hormone dominated the luteal phase?
Progesterone
What inhibits FSH?
Inhibin from granulosa cells
Enzyme which converts androgens to oestrogens
Aromatase
What occurs at cell 4 stage?
Zygotic genome activation
Zygotic genome activation =
Genetic reprogramming. Genome is wiped of all methylation marks and re-methylated
What implants into uterus?
Blastocyst
What day does blastocyst form/implant?
5-9
Describe the strucutre of a blastocyst before it hatches
Zona pellucida
Trophoepiblasts
Inner cell mass
Blastocoel cavity
What is the ICM become?
Trilaminary disc/foetus
What does a blastocyst produce?
hCG
hCG =
Human chorionic gonadotropin
hCG has a similar chemical structure to…
LH
Why do hCG levels drop mid pregnancy?
Placenta is established and begins steroid synthesis
How do the fetus and placenta work together to produce oestrogens?
Foetus = C19 androgens from adrenal Placenta = Aromatises these to oestrogens
2 types of twins =
Monozygotic
Dizygotic
Dizygotic twins most likely due to =
Hyperovulation due to increased FSH
Types of monozygotic twins =
Dichorionic-diamnionic
Monochorionic-diamnionic
Monochorionic-monoamnionic
Dichornionic-diamnionic =
Splits before blastocyst stage. Own placenta and amniotic sac
Monochorionic-diamnionic
Occurs when blastocyst hatches. Share placenta but different amniotic sacs
Monochorionic-monoamnionic =
Occurs at blastocyst stage. Same placenta and amniotic sac
What is the risk with monochorionic-monoamnionic twins?
Twin-Twin transfusion syndrome
Where are eggs aspirated from for IVF?
The follicle
In IVF how are the egg and sperm fertilised?
Co-incubated for 24 hrs
ICSI =
Intracytoplasmic sperm injection
When is ICSI used?
Low sperm count/male infertility
PESA =
Percutaneous epididymal sperm aspiration
MESA =
Microepididymal sperm aspiration
TESE =
Testicular sperm extraction (biopsy)
TESA =
Testicular sperm aspiration
Most common causes of infertility =
Male Unexplained Ovulatory disorder Tubual disease Endometriosis
Meds used for down-regulation =
GnRH agonists = Lupron, zoladex
GnRH antagonists = Antagon, cetrotide
Zoladex =
GnRH antagonist
Cerotide =
GnRH agonist
Superovulation =
FSH
Why down regulation?
Stop LH surge and spontaneous rupture of follicle
Some IVF criteria:
<42, >23 19-29 BMI Non-smoker for 6 mnths No existing children Stable 2 year relationship Regular unprotected intercourse for 2 years