LEC55: Placenta Flashcards
functions of placenta
1) respiration
2) nutrition
3) endocrine
4) excretion
5) protection
respiratory function of placenta?
materal oxygen - fetal CO2 exchange
nutrition provided via placenta?
glucose, amino acids from mother, thru placenta, so baby can build proteins
excretory products from placenta?
fetal waste products, include:
urea, uric acid, CO2
what is placenta’s protective function?
prevents passage of some microorganisms, allows passage of protective antibodies
methods of placental transfer?
1) simple diffusion
2) facilitated diffusion
3) active transport
4) pinocytosis
what passes thru placental via simple diffusion?
oxygen, CO2, water
what passes thru placenta via facilitated diffusion?
glucose, some electrolytes
what passes thru placenta via active transport?
some hormones ie estrogen, progesterone; also iron
requires energy, usually ATP
what is pinocytosis? what does pinocytosis for placenta?
phagocytic action
immunoglobulins - early immune system, from mother - transfer to fetus
main types of placental hormones
1) steroid hormones
2) protein hormones
placental steroid hormones?
1) progesterone
2) estriol*
* *only place in body woman has estrogen as estriol, usually it’s estradiol *
placental protein hormones?
1) hCG, human chorionic gonadotropin
2) hCS, human chorionic somatotropin
3) hPL, human placental lactogen
4) hCT, human chorionic thyrotropin
5) hCACTH, human chorionic corticotropin
fxn of hCG?
pregnancy test hormone
“tells” corpus luteum to maintain progesterone production
fxn of hCS?
promotes fetal growth, growth of body
fxn of hPL?
early insulin-like hormone for fetus
helps placenta deal w/ sugar
fxn of hCT?
functions as fetus’s thyroid
fxn of hCACTH?
does job til fetal adrenal glands develop
stimulates cortisol production
size of placenta, at term?
500 grams or 1 lb
2 parts of the placenta?
1) fetal part, chorionic villi, from cytotrophoblast & synciciotrophoblast
2) maternal part, decidua basalis, endometrium that has become rich, lush, ready for implantation; enriched w/ glycogen under progesterone influence, transforms endometrium > decidua
when do trophoblasts invade into endometrium?
week 2
composition, function of syncytiotrophoblasts in invasion of endometrium
finger-like projections that’re made of mass of cytotrophoblastic material
under hCG
invades decida
engulfs endometrial glands, maternal blood vessels
what do cytotrophoblasts do, what does it give rise to?
actively dividing
gives rise to syncytiotrophoblast layer
when does chorionic villi form?
as outer cell mass invades trophoblasts via cytotrophoblasts & syncytiotrophoblasts
week 2
what readies endometrium for implantation? when does this occur?
during secretory phase:
1) hCG and progesterone cause endometrium to secrete glycogen via uterine glands
2) spiral arteries form - maternal blood surges through, causes spiraling shape of vessels
cause of peeclampsia? clinical significance?
if remodeling of blood vessels from straight > spiral does not occur, > preeclampsia
elevated maternal BP, protein spillage in urine, taking on fluid all over body
phases of chorionic villus
1o, 2o, 3o
structure of 1o chorionic villus?
2 layers - syncytiotrophoblastic shell, cytotrophoblastic core
structure of 2o chorionic villus?
3 layers: mesenchymal core, cytotrophoblastic layer, syncytiogrophoblastic shell
structure of 3o chorionic villus?
week 17/20-onward
4 components:
syncytiotrophoblastic shell, cytotrophoblastic layer, mesenchymal core & fetal capillaries grow into villi
when is fetal capillary-venous network established?
tertiary chorionic villi stage
how does umbilical vein connect to placenta?
umbilical vein connects to veins of the tertiary villus; veins connected w/ fetal capillary beds hook up to arteries, join w/ arteries in umbilical cord
where do tertiary chorionic villi sit?
sinde of intravillus space
how does maternal blood > fetal circulation?
blood pressure shoots maternal blood out of spiral arteries
extruded maternal blood bathes fetal capillary beds
what is this network?
tertiary chorionic villus
what structure do chorionic villi cover?
chorionic sac
how much of chorionic sac do chorionic villi cover?
initially, villi cover entire outer surface of embryo
as embryo expands, villi degenerate - that area = chorion laevae (smooth chorion)
develop into placenta over chorion frondosum (villus chorion)
name of area where chorionic villi disappear?
chorion laevae, aka smooth chorion
area where chorionic villi remain? function?
chorion frondosum, aka villus chorion
= area where placenta develops
name the structures
what occurs in intervillus space?
blood interpolates between villi
where is chorionic plate? function?
between fused amnion and chorion
spikes of placental tissue grow toward chorionic plate
what are cotyledons
areas of intervillus space served by 2 or more chorionic villi
how does maternal blood > fetal veins
blood injected into intervellus space
blasted out of vessel
bathes capillary beds
> venous system
what in maternal-fetal circulation system has highest oxygen content?
UMBILICAL VEIN! not umbilical artery!
what is placental membrane?
extrafetal tissues that separate maternal & fetal blood
site where placental exchange occurs
structure of placental membrane prior to 20 weeks?
syncytiotrophoblast
cytotrophoblast
villus connective tissue (tertiary)
fetal capillary endothelium
placental membrane structure >20 weeks?
cytotrohpoblasts disappear (attenuated)
fetal capillaries in intervillus space b/c growing toward syncytiotrophoblast
vasculosyncytial placental membrane of syncytiotrophoblast, villous connective tissue, fetal capillary endothelium remains
mesoderm in some areas
umbilical vein fxn?
carries oxygenated blood TO fetus
umbilical arteries’ function?
carry deoxygenated blood FROM fetus
composition of umbilical cord?
1 umbilical vein, 2 umbilical arteries
wharton’s jelly location, function?
mucoid connective tissue
protects, cushions maternal blood vessels against compression
amt of wharton’s jelly decreases as pregnancy progresses
incidence of 1 umbilical artery? risks?
1/50, 2% pregnancies
increased risk of cardiac defects & of poor growth later in pregnancy
what is amnion
aka membranes, bag of waters, or amniotic sac
describe growth of amniotic cavity
forms during bilaminar embryo stage
grows as embryo grows
forms “C” around embryo
tightly opposes umbilical cord
eventually, fuses w/ chorion, completely obliterates chorionic cavity
what is the bag of water that breaks?
chorio-amniotic membrane, where amnion and chorionic cavity fuse
what must occur to do an amniocentesis?
amnion-chorion must be fused
where in endometrium does embryo implant?
decidua basalis
what is decidua capsularis
capsule surrounding fetus
what is decidua parietalis
most external part of decidua
will fuse w/ decidua basalis, allow embryo to fill entire uterine cavity
where does amniotic fluid come from?
early, derived form diffusion of fluid from decidua (surrounding tissues) through amnion
> 12 weeks, FETAL URINE!! & excreted lung fluid (<20%)
when does volume of amniotic fluid peak? amount?
36 weeks
1 liter
function of amniotic fluid?
provides fluid filled space for fetus to grow
provides protection, cushion for baby
allows room for lungs to expand
amniotic fluid composition?
99% water
also desquamated fetal skin cells, carbohydrates, fats, enzymes, hormones, salts (electrolytes, urea)
how does amniocentesis work?
draw 20-30cc fluid from amniotic cavity, put in culture
desquamated skin cells from fetus grow in culture > test
does mature placenta produce luteotrophic hormone?
LH - no! that’s what triggers ovulation
uteroplacental circulation
describe process of utero-placental circulation
