Physiology of Pregnancy Flashcards
What is a blastocyst?
embryo which has developed 2 different cell compartments and a fluid cavity (inner and outer cell masses)
What days post fertilisation is the blastocyst transported into the uterus?
3-5 days
How many days post fertilisation does the blastocyst attach to the lining of the uterus?
5-8days
What happens when the blastocyst adheres to the endometrial lining?
cords of trophoblastic cells begin the penetrate the endometrium
What happens to the boundaries between the cells fo the advancing trophoblastic tissue?
begin to disintegrate
How many days post fertilisation is the blastocyst buried in the uterine lining?
day 12
What is the placenta derived from?
trophoblast and decidual tissue
What type of trophoblast cell invade the decidua and break down capillaries to form cavities filled with maternal blood?
syncytiotrophoblasts
What froms the placental villi?
developing embryo send capillaries into the syncytiotrophoblast projections
What is found within the placental villi?
foetal capillaries separated from maternal blood by a thin membrane within the intervillous space
When is the placenta functional?
5th week of pregnancy
What is the function of progesterone in relation to the decidual cells?
stimulates decidual cells to concentrate glycogen, proteins and lipids
What is the purpose of the placental villi?
increase surface area
What are the 3 factors that faciliatate oxygen transport in the fetus?
fetal HB (higher affinity to o2); higher Hb conc. in fetal blood and Bohr effect (fetal Hb can carry more o2 in low pCO2 than in high pCO2
What is the pupose of the Bohr effect?
Oxygen has a lower affinity when there is high CO2 conc. or low pH which means that in metabolically active tissues eg SK muscle, more oxygen is unloaded in response to higher CO2 in that region
How does glucose pass the placenta?
simplified transport
What is the function of hCG?
prevent involution of the corpus luteum; effect on testes of male fetus
When is hCS produced?
from week 5 of the pregnancy
What are the function of human chorionic somatomammotropin?
growth hormone-like effects-protein tissue formation; decreases insulin sensitivity in mother- more glucose for fetus; breast development
What is the function of progesterone in pregnancy?
development of decidual cells; decreases uterine contractility; prep for lactation
What is the function of estrogen in pregnancy?
enlargemnt of uterus; breast devleopment; relaxation of ligaments
What is the significance of estriol level in pregnancy?
indicator of vitality of fetus
What is the function of placental CRH?
results in aldosterone–HT; cortisol–oedema; insulin resistance
What causes hyperthyroidism in pregnnacy?
placenta produces human chorionic thyrotropin which functions similar to TSH
What causes hyperparathyroidism in pregnancy?
increased calcium demands by the placenta
Why is there an increase in CO during pregnancy?
demands of uteroplacental circulation
When does CO decrease during pregnancy?
alst 8 weeks
Why does CO dcrease at end of pregnancy?
sensitive to body position-uterus compresses IVC when supine
Why does BP drop during 2nd trimester?
uteroplacental circulation expands and peripheral resistance decreases
Why does Hb in blood decrease in pregnancy?
decreased by dilution- plasma volume inc. 50%; erythropoesis inc 25%; iron requirements increase signif
What is the function of progesterone on the rep system?
increased CO2 sensitivity in respiratory centres
What happens to the repiratory system in pregnancy?
RR increases; ridal volume inc; pCO2 decreases; vital capacity and PO2 dont change
What happens to the urinary system during pregnancy?
GFR and RPF increase; increased re-absorption of ions and water (placental steorids)
What is pre-ecampsia?
pregnancy induced HT and proteinuria
Who is pre-eclampsia more common in?
women with pre-existing HT; DM; autoimmune disease; renal disease; fhx; obestiy and multiple gestation
What is the single biggest risk factor for pre-eclampsia?
having it already
What causes pre-eclampsia?
extensive secretion of placental hormones; immune repsonse to fetus; insuffficient blood supply to placenta- ischaemia
What happens in eclampsia?
vascular spasms; extreme hypertension; chronic seizures and coma
What is the treatment for eclampsia?
vasodilators and caesarean section
What is the average weight gain during pregnancy?
24lbs
How many extra calories per day should be ingested by the mother?
250-300kcal/day
What causes insulin resistance in the mother?
HCS; cortisol and growth hormone
What happens during the mothers anabolic phase?
normal or increased sensitivity to insulin; lower plasma glucose; lipogensis; glycogen stores increase; growth of breast; uterus; weight gain
What happens during htem others catabolic phase?
materanl insulin resistance; increased transport of nutrients through placental membrane; lipolysis
What vitamin is given to mothers before parturition and why?
K vitamin to prevent intracranial bleeding during labour
What is the difference between the excitability of the uterus with progesterone and oestrogen?
progesteron inhibits contractility while estrogen increases contractility
What is the function of oxytocin in labour?
increases contractions and excitability and prostaglandin production
What is the positive feedback in the onset of labour?
stretch of cervix by fetal head increases contractility and further oxytocin release which increases contractions
What is the interplay betwen oxytocin and oestrogen?
oestrogen induces oxytocin receptors on uterus
What is the 1st stage of labour?
cervical dilation
What is the 2nd stage of labour?
passage thorugh birth canal
What is the third stage of labour?
expulsion of placenta
What is the role of oestrogen in lactation?
growth of ductile system; inhibits milk production
What is the role of progesteron in lactation?
development of lobule-alveolar system; inhibits milk production
What hormone stimulates milke production?
prolactin
What hormone is responsible for the mlik let down reflex?
oxytocin (smooth muscle contraction in breast)
What are the functions of pregnancy-induced hypervolaemia?
meets demands of enlarged uterus with greatly hpertrophied vascular system; provide nutrients to placenta and fetus; protect mother and fetus from impaired venous return in certain postures and ensure mother doesn’t suffer adverse effects from blood loss at devliery
How do oestrogen and progesterone contribute to hypervolaemia?
oestrogehn increases heptic production of angiotensinogen; both hormones increase renin production
What does the body do to increase oxygen carrying capacity in increase blood volume?
increase iron absorption to increase haemoglobin
Why does the increase in angiotensin II not cause vasconstriction?
loss of peripheral vascular responsiveness to ATII- perhaps due to increases in prostacyclin
What causes the drop in BP in the 2nd trimester of pregnancy?
loss of peripheral vascular responsiveness to ATII and progesterone - smooth muscle relaxation
What should the blood gases in pregnancy be?
pH should be alkalotic with a decrease in pCO2 and bicarb
How is progesterone involved in respiratory changes in pregnancy?
affects respiratory centres to increase sensitivity to CO2
How is the mild metrnal respiratory alkalosis caused by increased ventilation compensated?
increased renal bicarb excretion
What is the effect of decreased plasma bicarb on the oxygen dissociation curve?
shifts to the left; increasing affinity of materanl haemoglobin for oxygen
What is the problem with increasing the affinity of maternal haemoglobin for oxygen?
decreases the the oxygen releasing capacity of hte maternal blood
how is the increased affinity for oxygen caused by decreased bicarb offset?
increase in 2,3 diphosphoglycerate during pregnnacy which shifts curve back t othe right
What increases the risk of mothers developing kidney infections?
renal collecting system dilates due to smooth muscle relaxation of progesterone and mechanical obstruction by the uterus so urine travel slows down
What effect does oestrogen have on the liver?
increases synthessi of hepatic proteins- incl, procoagulants
Why are minor disorders of the GI tract common in pregnancy eg constipation and heartburn?
progesterone relaxes smoothe muscle and affects all parts of the GI tract in pregnancy
