pregnancy physio Flashcards
what layers of the egg must a sperm penetrate?
penetrates corona radiata and zona pellucida
what stops poly spermy?
- Usually only one sperms gets through and depolarises outer layers and stops polyspermy
what is a zygote
fertilised ovum
combo of 23 chromosomes from egg and 23 chromosomes from sperm to from fertilised cell
where does fertilisation usually take place?
within ampulla
how long does it take to form blastocyte
usually 7-10 days post ovulation - should be in uterus now
what are the outer cells of a blastocyst called?
trophoblast
when does implantation occur?
when blastocyte arrives at uterus at 8-10 days after ovulation it reaches endometrium
what does the trophoblast do?
Trophoblast: outer layer of blastocyte
- These cells undergo adhesion to stroma (supportive outer tissue of endometrium)
-
what is the outer most layer of the trophoblast?
syncytiophoblast
what does the syncytiophoblast do?
- Outer layer of trophoblast - syncytiophoblast
- Cells of stroma convert tissue into decidua specialised in providing nutrients to trophoblast
what does the syncytioblast produce when impanted into endometrium
When blastocyte implants onto endometrium syncytioblast produces HCG
what is the role of HCG?
- HCG very important to maintain corpus luteum allowing it to continue to make progesterone and oestrogen
describe the basic embryology in the early stages?
a week following fertilisation implanted blastocyte starts to differentiate into various types of cells
- Embryoblast splits into two yolk sac and amniotic cavity
- Embryonic disc sits between yolk and amniotic cavity
- Cells of embryonic disc develop into foetal pole eventually foetus
what are the hormonal changes within pregnancy?
- Increase in steroid hormones
- Increase in T3/T4 TSH remains the same
- Increase in prolactin
- Melanocyte SH
- Oestrogen
- Progesterone
- HCG
what does the increase in melanocyte SH do?
more pigmentation in mother
how does oestrogen continue to rise?
produced by placenta
what is the role of progesterone in pregnancy?
maintains pregnancy, prevents contractions and suppresses mothers immune reaction to foetal antigens
how does HCG increase through the pregnancy?
doubles every 48hrs until they plateau at around 8-12weeks then start to fall (can then test -ve on tests)
what does rise in ACTH result in?
- ACTH causes rise in cortisol and aldosterone
what does increased prolactin result in?
- Increased prolactin: suppressed FSH and LH
no follicular stimualtion hence no menstruation cycle
where does pregnancy progesterone come from?
Corpus luteum produces progesterone until 10weeks then placenta takes over
what are the CVS changes through pregnancy?
- Increase in blood volume
- Increase in plasma
- Increase in CO
- Decrease in vascular resistance
- Decrease in BP in early and middle pregnancy returning to normal by term
- Vasodilation
varicose veins
what does vasodilation cause in preg?
flushes and hot sweats
why are there more varicose veins within preg?
due to peripheral vasodilation and obstruction of inferior vena cava by uterus
what are the haematological changes?
- Anaemia
- Clotting factors such as fibrinogen, factor VII, VIII and X increase in pregnancy
- Increase in ALP: up to 4x higher due to secretion by placenta
- Reduced albumin due to loss of proteins
- Higher WCC, decreased platelets, increases ESR and D dimer,
what does increase in clotting factors mean during preg?
higher risk of VTE, DVT and PE
what are the resp changes?
- Increase in tidal volume
- Increase in resp rate