Placental physiology + pathology Flashcards
General roles of the placenta
nutrient uptake
thermoregulation
waste elimination
gas exchange
fight against internal infection
produce hormones which support pregnancy
What cells of the blastocyst form the placenta?
outer trophoblast cells
How many umbilical arteries are there?
2
Function of hCG in pregnancy
maintains corpus luteum of pregnancy
stimulates secretion of testosterone by developing testes in XY embryo
Function of oestrogen in pregnancy
stimulates growth of myometrium, increasing uterine strength for parturition (childbirth)
helps prepare mammary glands for lactation
Function of progesterone in pregnancy
suppresses uterine contraction to provide a quiet environment for foetus
promotes formation of cervical mucus plug to prevent uterine contamination
helps prepare mammary glands for lactation
Features of a term placenta
discoid shape
15-20cm
maximum thickness 3cm in centre
weighs roughly 500g
2 surfaces: foetal and maternal
parts: membranes, umbilical cord and placental disc
Features of foetal side of placenta
smooth, glistening and umbilical cord attached at centre
umbilical vessels seen below amnion
amnion can be peeled off except at cord insertion
Features of maternal side of placenta
rough and spongy
15-20 convex lobes separated by fissures
dull red and occasionally thin greyish membranous structure attached which is the peeled off decidua basalis
What is the bulk of the umbilical cord made up of?
highly mucoid connective tissue –> Wharton’s jelly
What blood vessels are in the umbilical cord?
2 arteries
1 vein
What does the placental membranes consist of?
amnion - innermost covering of amniotic cavity (ine cell layer)
chorion - connective tissue membrane that carries foetal vasculature (3 layers - reticulin, pseudo basement membrane, trophoblastic)
What can cause abnormally large placentas?
accompany conditions leading to foetal anaemia or cardiac failure
erythroblastosis foetalis
infections - syphilis, toxoplasmosis, cytomegalovirus
tumour of placenta and foetus
foetal renal vein thrombosis
What can cause abnormally small placentas?
premature and small for dates infants
maternal vascular disease
foetal malformations
What is placenta accreta?
placental villi adhere to underlying myometrium, without an intervening layer of decidua
(increta = villi invade myometrium, percreta = whole myometrial invasion)
What routes can cause placental infection?
ascending
haematogenous
What placental infections are caused by ascending spread?
herpes virus
candida
fusobacteria
What placental infections are caused by haematogenous spread?
CMV
listeria
rubella
syphilis
toxoplasmosis
TB
coccidioidomycosis
cryptococcosis
malaria
psittacosis
Complications of chorioamnionitis
caesarean delivery
endomyometritis
wound infection
pelvic abscess
bacteraemia
PPH
septic shock
DIC
ARDS
maternal death
Umbilical cord abnormalities
false knot
true knot
velamentous insertion
single umbilical artery
