Physiology of Pregnancy and Puerperium Lactation Flashcards
what is the role of the fimbriae?
sweep ovum into oviduct, carried along by smooth muscle contraction and cilia
what is a fertilised ovum called once it divides and differentiated?
blastocyst
*progressively divides into blastocyst as it moves from site of fertilisation in upper oviduct to site of implantation in uterus
between which days after fertilisation does the blastocyst attach to lining of uterus?
5-8
what do the inner cells and outer cells of blastocyst develop into?
inner cells = embryo
outer cells = burrow into uterine wall and become placenta
what is the role of the placenta?
produce several hormones to maintain pregnancy
what happens once the free-floating blastocyst adheres to the endometrial lining?
cords of trophoblastic cells begin to penetrate the endometrium
advancing cords of trophoblastic cells tunnel deeper into the endometrium, carving out a hole for the blastocyst
the boundaries between cells in the advancing trophoblastic tissue disintegrates
what is the decidua?
modified mucosal lining of the uterus (that is, modified endometrium) that forms in preparation for pregnancy.
*formed in a process called decidualization under the influence of progesterone
when implantation is finished, the blastocyst is completely buried in the endometrium - what day does this occur?
day 12
what type of tissue is the placenta derived from?
trophoblast and decidual tissue
how is the placenta formed?
trophoblast cells (chorion) differentiate into multinucleate cells (syncytiotrophoblasts) which invade decidua and break down capillaries to form cavities filled with maternal blood
developing embryo sends capillaries into the syncytiotrophoblast projections to form placental villi
each villus contains foetal capillaries separated from maternal blood by a thin layer of tissue (no direct contact between foetal and maternal blood)
the placenta acts as a 2 way exchange of what?
respiratory gases, nutrients, metabolites
largely down diffusion gradient
the placenta and foetal heart are functional by which week of pregnancy?
5th
what is the role of human chorionic gonadotrophin (HCG)?
signals the corpus luteum to continue secreting progesterone
what is the role of progesterone?
signal decidual cells to concentrate glycogen, proteins and lipids
where do blood vessels from the embryo develop?
villi (hair like projections) from placenta into uterine wall
*thin membrane separates the embryos blood in the villi from mothers blood in intervillous space
the circulation within the intervillous space acts partially as what?
arteriovenous shunt
what is the difference in components of maternal vs umbilical blood?
maternal = oxygen rich
umbilical blood = mixing of arterial and venous blood, oxygen-poor
how do oxygen and CO2 exchange between maternal and foetal circulation?
oxygen diffuses from maternal into foetal circulation (PO2 maternal > PO2 fetal)
CO2 (partial pressure is elevated in fetal blood) follows a reversed gradient
once oxygen and CO2 has been exchanged between maternal and fetal circulation, how does it return back?
fetal, oxygen saturated blood, returns to the fetus via the umbilical vein
maternal, oxygen-poor blood, flows back into the uterine veins
what three factors facilitate the supply of oxygen to the foetus?
- fetal Hb (increased ability to carry O2)
- higher Hb concentration in blood (50% more than in adults)
- bohr effect (foetal Hb can carry more oxygen in low PCO2 than in high PCO2)
how does water diffuse through the placenta?
along its osmotic gradient
*exchange increases during pregnancy up to 35th week (3.5l/day)
what follows H2O in the diffusion through the placenta?
electrolytes (iron and Ca2+ only can go from mother to child)
how does glucose (foetus’ main source of energy) pass the placenta?
via simplified transport (high glucose needed in 3rd trimester)
fatty acids have free diffusion - true or false?
true
diffusion of waste products is based on what?
concentration gradient
what is the role of human chorionic gonadotropin?
prevents involution of corpus luteum (stimulates progesterone, oestrogen)
*effect on testes of male foetus = development of sex organs