ER 18+19 Flashcards
what are the four fetal membranes?
- Amnion- membrane that closely covers the embryo when first formed
- umbilical vesicle or yolk sac - membranous sack attached to the embryo formed by cells of the hypoblast adjacent to the embryonic disk
- Allantois - extension of the posterior wall of the yolk sac. degenerates to form the medial umbilical ligament
- chorion - outermost fetal membrane which develops from an outer fold on the surface of the yolk sac
amniotic fluid
source? composition? excretion
function?
from the amnion, maternal blood, urine, skin, secretions’ from respiratory
mostly made out of water with small amounts of nutrients
circulates every 3 hours
excretion by fetus swallowing it
function?
shock absorber
maintain temp
lung development
amniochorionic membrane
the amnion fuses with the chorion and obliterates the chorionic cavity to form one membrane
the baby will now float in the fluid
Oligohydramnios
cause?
complications?
low volume of amniotic fluid
cause:
preterm rupture of membrane
urinary system abnormalities (bilateral renal agenesis)
placental insufficiencies (low blood circulation)
complication:
lung hypoplasia
facial or limb deformity
Polyhydramnios
cause? complications?
high volume of amniotic fluid
cause: idiopathic maternal diabetes or multiple pregnancies esophageal atresia CNS abnormalities
complication:
preterm labor
premature rupture of membrane
Hydatiform Mole?
the embryo dies and the chorionic villi do not complete development (they do not become vascularized to form tertiary villi)
degenerating villi may form cystic swellings called hydatiform moles
these produce excessive amounts of HCG
very few times these become cancerous
The decidua?
Decidua basalis - the endometrium deep to and in contact with villous chorion
decidua capsularis - endometrium related to the smooth chorion and separates it from uterine cavity
decidua parietalis - the rest of the endometrium not in direct relation with chorion sac
formation of the placenta
maternal part - decidua basalis
fetal part - formed from the villous chorion. attached to the maternal part of the placenta by a cytotrophoblastic shell
cotyledons - divide the fetal part of the placenta into irregular convex areas
hemolytic disease of the newborn?
some fetus blood may pass into the maternal blood through breaks in the placental membrane
if the fetus is Rh + and the mother is Rh -, the fetal cells may form antibodies by the mothers immune system
this leads to hemolysis of fetal Rh-positive blood cells and anemia in the fetus.
Fetus may die unless delivered early or given transfusions of packed Rh negative blood cells.
placental abnormalities?
accreta? increta? percreta? previa?
placenta accreta - abnormal adherence of chorionic villi to myometrium of the uterine wall.
placenta increta - chorionic villi invade deeply into the myometrium
placenta percreta - chorionic villi penetrate the entire uterine wall and may go through perimetrium
3rd trimester bleeding
placenta previa - implantation near or overlaying the internal os
severe bleeding in later pregnancy
Twin transfusion syndrome?
Preferential shunting of arterial blood in one twin to venous blood in the other.
donor twin - small and anemic
recipient twin - large and polycythemic
conjoint twins
Incomplete division of the embryonic disc or fusion of adjacent embryonic discs
what secretes hCG?
what does this hormone do?
implication?
Secreted by syncytial cells of trophoblast into maternal circulation
it prevents the involution of the corpus luteum
keep progesterone levels up
levels keep going up until the 13th week
has been implicated with morning sickness
role of hCG in male fetus?
general roles?
stimulates testosterone production
promotes decent of testes
supports corpus luteum
produces estrogen, progesterone, relaxin
role of progesterone in mother and fetus?
mother: maintains pregnancy supports endometrial lining required for breast development inhibits lactation during pregnancy
fetus:
progesterone is a precursor molecule for synthesis of adenocortical hormones by fetal adrenal cortex
