Physiology - Pregnancy and Lactation Flashcards
what does the fertilised ovum divide and become?
a blastocyst
what occurs in the first 3-5 days following fertilisation?
transport of the blastocyst into the uterus
what happens 5-8 days post fertilisation?
the blastocyst attaches to the lining of the uterus
what do the inner cells of the blastocyst become?
the embryo
what do the outer cells of the blastocyst become?
the placenta
what happens when the blastocyst adheres to the endometrium?
cords of trophoblastic cells begin to penetrate the endometrium
when is implantation of the blastocyst completed?
by day 12
what is the placenta derived from?
trophoblasts
decidual tissue
what is another name for the trophoblast cells?
chorion
what do the trophoblast cells differentiate into?
multinucleate cells called synctiotrophoblasts
what do the syncytiotrophoblast cells do?
invade the decider and break down capillaries, forming cavities filled with maternal blood
what forms the placental villi?
capillaries from the developing embryo entering the syncytiotrophoblast projections in the decider
what do placental villi contain?
foetal capillaries separated from maternal blood by a thin layer of tissue
when are the placenta and foetal heart functional?
by the fifth week of pregnancy
what provides early nutrition to the embryo?
trophoblastic cells that have invaded into the decidua
what takes over providing nutrition to the embryo later in the pregnancy?
the placenta
what effect does HCG have on the corpus luteum?
signals it to keep secreting progesterone
what effect does progesterone have on the decidual cells?
stimulates them to concentrate glycogen, proteins and lipids
what is the outcome of the placental villi extending into the uterine wall?
increases contact area between the uterus and placenta allowing gate exchange of nutrients and waste
what plays the role of the foetal lungs?
the placenta - allows supply of oxygen and removal of CO2 from the foetus
which has higher oxygen concentration - maternal or foetal blood?
maternal
in which direction does oxygen diffusion in the placenta occur?
from the maternal circulation to the foetal circulation
PO2 maternal > PO2 foetal
in which direction does CO2 diffusion occur in the placenta?
from the foetal circulation to the maternal circulation
maternal CO2 < foetal CO2
where does foetal blood go after getting oxygen from the placenta?
returns to the foetus via the umbilical vein
where does maternal blood go after giving oxygen to the placenta?
back into the uterine veins
what three factors facilitate the supply of the foetus with oxygen?
foetal Hb
higher Hb concentration in foetal blood
Bohr effect
how is foetal Hb different from adult Hb?
has an increased ability to carry oxygen
which has a higher Hb concentration - foetal blood or maternal blood?
foetal
this enables greater oxygen transport
how does the Bohr effect facilitate oxygen transport in the foetus?
foetal Hb can carry more oxygen in low pCO2 than in high pCO2
this is good because foetal CO2 < maternal CO2
in which direction does water travel across the placenta and via what mechanism?
from mother to foetus
via osmosis
what amount of water is exchanged across the placenta in pregnancy?
increases up to the 35th week where it is around 3.5L per day
how do electrolytes cross the placenta?
follow the water that moves via osmosis
which electrolytes go ONLY from mother to child across the placenta?
iron and calcium
need to ensure mothers have adequate levels of these substances
how does glucose pass across the placenta?
via simplified transport
what is the foetuses main source of energy?
glucose
at which point in pregnancy is most glucose required?
in the third trimester
how do fatty acids move across the placenta?
via free diffusion
name four hormones that change throughout pregnancy
HCG
HCS/HPL
oestrogen
progesterone
what does HCG stand for?
human chorionic gonadotrophin
what does HCG do?
prevents involution of the corpus luteum
this stimulates progesterone and oestrogen production
what effect does HCG have on male foetuses?
aids in the development of the sex organs
describe the levels of HCG throughout pregnancy
highest in early pregnancy
what is another name for human placental lactogen (HPL)?
human chorionic somatomammotropin
when is HPL produced?
from around week 5 in pregnancy
continues to rise throughout pregnancy
what are the three main effects of HPL?
growth hormone like effects - protein tissue formation
decreases maternal insulin sensitivity
involved in breast development
what effect does decreasing insulin sensitivity in the mother have on the foetus?
allows more glucose to be provided for the foetus
what three effects does progesterone have throughout pregnancy?
development of decidual cells
decreases uterine contractility
prepares the body for lactation
describe levels of progesterone and oestrogen throughout pregnancy
rise throughout pregnancy
what three effects do oestrogen have during pregnancy?
enlargement of the uterus
breast development
relaxation of the pelvic ligaments
what happens to serum HCG levels in early singleton pregnancy?
double every 48 hours
what are HCG levels like in an ectopic pregnancy?
static or slow rising
what are HCG levels like in a failing pregnancy?
reducing
what side effects can HCG cause?
nausea and vomiting