placenta liquor Flashcards
what is the placenta
organ that is essential for transfer
of nutrients and gases from the
mother to the fetus and for removal
of fetal waste products.
what is the endometrium
prepares for implantation during secretory phase of menstrual phase
describe what happen in the decidual reaction
trophoblast secrete HCG to support corpus luteum . corpus luteum secretes progesterone until 20 weeks. progesterone and oestrogen trigger hypertrophy of epithelial and stromal cells
stromal cells store lipid and glycogen in the cytoplasm - becoming decidual cells , lining becomes more vascular . nutrient is supplied to endometrial tissues
endometrium is now decidua
decidua basalis
site of implantation from maternal side maternal macrophages migrate here
decidua peritallis
Rest of former endometrium, lining
the body of the uterus and fundus -
i.e. the side not occupied by the
embryo
decidua capsularis
Decidua capsularis
Overlies embryo and chorionic
vesicle
Generally regresses
what happens in fertilisation
sperm reaches oocyte and penetrates the zone pellucida. oocyte swells and becomes impenetrable to other sperms . each haploid nucleus transforms into a pronuclei
what happens during implantation
Blastocyst progresses along fallopian tube
and into the uterus
Trophoblast cells meet the endometrium -
due to enzyme production and the
stickiness of endometrium, blastocyst
begins to implant
Endometrial folds around blastocyst swell
and epithelial cells multiply above,
forming a cover for the embedded
blastocyst
Trophoblast cells net to the endometrium
become multi-nucleated cells -
syncitiotrophoblast cells
Villi begin to form from syncitiotrophoblasts,
branching into the decidua - which contains
blood vessels
Syncitiotrophoblasts grow down into the basal
layer of the decidua
Lacunae fuse to develop the intervillous space, in
which maternal blood flows
Invading cords of trophoblasts form primary villi,
later branching out to form secondary villi
Corpus luteum gravidiatis continues to secrete
hormones
what is the amnion
Inner membrane (closest to fetus)
Can be stripped back to insertion of cord
Derived from inner cell mass
Smooth, transparent
Tougher than chorion
Secretes liquo
what is the chorion
Outer membrane (closest to mother)
Derived from trophoblast
Opaque, friable
Roughened by adherent decidua
Lines uterine cavity
what is the umbilical cord
Differs to adult circulation in terms of vessels
2 arteries (deoxygenated blood)
1 vein (oxygenated blood)
Usually central insertion into placenta
Wharton’s jelly - protection
30 - 90cm long, 1 - 2cm diameter
Term blood flow usually 350ml/min
what anomalies could be in the umbilical cord
Anomalies may include insertion site, false knots, hypercoiling, true knots, only 1 artery, 4 vessels, haematoma
what is the maternal side of the placenta
aternal side
Fetal side
Decidua basalis
Darker colour
About 20 lobes - cotyledons
Each cotyledon has own blood supply
Sometimes gritty texture - lime salt deposits
Infarcts may be noted
what is the fetal side of the placenta
Villous chorion
Amnion covers surface
White, shiney appearance
Branches of umbilical vessels visible
Cord insertion is on this side
what happen in utero
ork?
Fetal side
Maternal blood delivered to decidua via
spiral arteries
Blood flows around intervillous spaces
Fetal blood (deoxygenated) pumped by
fetal heart through umbilical arteries to
capillaries of the chorionic villi
Deoxygenated blood becomes
oxygenated
Oxygenated blood travels through the
umbilical vein to fetus
Waste (i.e.) carbon dioxide drains back into
maternal uterine vein
what is the function of the placental membrane
Structure to prevent mixing of fetal and maternal blood
what are the 4 layers of placental membrane
4 layers;
Syncitiotrohopblast
Cytotrophoblast
Connective tissue
Endothelium of fetal capillaries
After 20 weeks, the cytotrophoblastic cells disappear & the placental membrane will then only consist of 3 layers
what may influence placental blood flow
contractions
hypotension
hypotension
what are the function of placenta (respiration )
Deoxygenated fetal blood flowing through the placenta absorbs oxygen
Deoxygenated fetal blood expels carbon dioxide
Removal of waste products
what are the function of placenta (nutrition)
mino acids for cell building
Glucose for energy
Calcium & phosphorus for bones & teeth
Iron for blood
Fats cross the placenta less easily
Stores glycogen, which can be converted to
glucose when required
what are the function of the placenta (endocrine)
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Hormone testosterone molecular structural formula
HCG - Large amounts at first to encourage corpus luteum
gravidiatis to continue secreting progesterone and oestrogen.
Reduces as pregnancy progresses
Oestrogen - Secreted in large quantities & takes over from
corpus luteum gravidiatis by 12 weeks
Progesterone - Takes over from corpus luteum gravidiatis by
12 weeks. Levels drop immediately before labour.
Human Placental Lactogen - Growth promoter – rises when
HCG falls.
what is the function of the placenta (protection)
Serves as a radiator – 85% fetal heat production
transmitted to mother via placenta
Protects from rejection by mother
Protection from pathogens
Though some (i.e. syphilis & TB) can cross
placenta
Passage of maternal antibodies (IgG) in third
trimester
placenta anomalies name them
ACRETA , INCRETA , PERCETA
placenta accreta
General term - describes any placenta that is
abnormally adherent to myometrium
placenta increta
villi invade myometrium
placenta percreta
Villi penetrate myometrial wall & into
surrounding structures such as the bladder
Often occurs when decidua formation is
defective – i.e. implantation over uterine
scars or in lower segment.
Fetal side
succentruitate lobe
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Succenturiate Lobe
Fetal side
Small portion of placental lobe
separated from main body
Attached to main placenta through
vessels passing through membrane
Could be retained inutero following
birth, increasing risk of haemorrhage
or sepsis
bipartite placenta
Placenta divided into 2 main lobes
Vessels branch off from cord
Also referred to as a ‘bi-lobed’
placenta
velamentous insertion
Vessels of the cord break up and run
through the membrane before
reaching the placenta
Can be linked to other conditions
such as vasa praevia
vasa pravia
fetal vessels run within membrane in close proximity to the internal os
circumvillate
chorion Is not attached to the edge of the placenta . fetal surface is same distance from edge . thickened ring seen on fetal surface
battledore
cord insertion is on the edge of the placenta
liquor composition
Also known as amniotic fluid
98% water
1-2% organic & inorganic substances
Alkaline
Clear/pale/straw colour
Contains proteins, carbohydrates, lipids & hormones
Vernix & lanugo
Fetus drinks & excretes
Volume around 700-1000ml at term
what are the function of the placenta
Cushioning
Temperature
Lubrication
Aid musculoskeletal development
Fluids
Maintain even pressure
Prevent amnion adherence
Barrier to infection
what is placental formation
Amnioblasts (cells of amnion) initially actively secrete liquor into
developing amniotic sac
Then, liquor is derived from maternal tissues, through process of
diffusion across membranes and decidua parietalis
Until 20 weeks, liquor passes freely into fetal tissues - until skin then
becomes keratinised
Some of the fluid also comes from fetal urine (from 11 weeks)
Fetal urine, lung secretions will then continue to help maintain the
volume
excess fluid in placenta is known as
polyhydramnios
reduced amount of amniotic fluid
oligohydramnios
