Module 9 : Normal Fetal Anatomy - Placenta and Cord Flashcards
at what week do we see two distinct components o the placenta
12 weeks
two distinct components of the placenta
chorion frondosum
decidua basalis
chorion frondosum
fetal portion
decidua basalis
maternal portion
how are the two layers held together
- anchoring or stem villi at the cytotrophoblastic shell
intervilluous spaces
- syncytiotrophoblast cells create large spaces in the decidua basalis
placental septa
- remaining projections of the decidua basalts
- septa divide the placenta into compartments
cotyledon
- each compartment the septa divide into in the placenta
- consist of several stem villi
- about twenty in a placenta
placenta membrane
- separates the fetal blood in the capillaries of the CHORIONIC VILLI from the maternal blood in the INTERVILLOUS SPACES
- maternal blood enters the intervillous spaces via the spiral arterioles
maternal circualtion
- spiral arterioles shoot blood around the chorionic villi
fetal circulation
- from umbilical arteries to chorionic villi back to umbilical veins to baby
functions of the placenta
- respiration (exchange oxygen)
- nutrition
- excretion (carbon dioxide)
- protection (toxic elements)
- storage
- hormonal production
sonographic appearance
- early = homogenous
- venous lakes along the basal plate and in the septa
- may see calcifications later in pregnancy due to maternal serum calcium levels
grading of placenta
- grade 0 - 3
grade 0 placenta
- homogenous
- chorionic plate is straight
grade 1 placenta
- scattered echogenic areas
- subtle undulations
grade 2 placenta
- indentations
- linear echogenic areas
grade 3 placenta
- indentations to basal layer
- cystic areas
- shadowing calcifications
- after 36 weeks
placenta shape
- flat and circular
weight of placenta a
- 500-600 grams at term
thickness of placenta
1.5-4 cm
abnormal placenta thickness
> 4 cm
growth of placenta per day
1mm
measuring placenta
- do not include retroplacenta complex (basal layer)
placentamegaly
> 4cm thick
causes of placentamegaly
- maternal diabetes
- maternal anemia
- hydrops
- placenta hemorrhage
- intrauterine infection
- partial mole
- chromosomal abnormalities
complete molar pregnancy
- triploidy 69 chromosomes
- uterus full of placenta
- no embryo
- if not removed can lead to chorionic carcinoma
thin placenta
- placenta insufficiency
- may cause IUGR
- < 1.5 cm
causes of thin placenta
- vascular deficiencies or infarction
- pre eclampsia = a toxaemia of late pregnancy (hypertension, protein urie, edema)
contraction vs fibroid
- fibroid \+ muscular tumor benign \+ lasts long time - contraction \+ Braxton hicks \+ will go away after time
umbilical cord
- develops from connecting stock and yolk sac
- 2 arteries 1 vein
- vessels surrounded by whartons jelly
- covered with amnion
- 50-100 cm long
attachment of cord
- usually centre of placenta
- umbilical vein travels cephalic to portal sinus
- umbilical arteries travel caudal around fetal bladder to hypogastric arteries in fetus
single umbilical artery
- associated with cardiac and renal anomalies
- associated with chromosomal abnormalities
- often isolated finding and very common
other cord anomalies
- hematoma
- cord cyst
- umbilical vein thrombosis
- omphalocele
- cord prolapse
hematoma
- from trauma of wall weakness
- results in perinatal death
cord cyst
- allantoid remnant
- insignificant
umbilical vein thrombus
- umbilical vein varix (dilation) or blockage
- results in perinatal death
omphalocele
- liver outside of abdomen
cord prolapse
- cord slips into cervix and vagina
- NOT GOOD
