Chapter 12 - 2 Flashcards
(27 cards)
Viability
is the capability of the fetus to survive outside the uterus at the earliest possible gestatational age
Usually 20-22 weeks (text 22 wks from LMP)
viability survival depends on
- maturity of the fetal nervous system
2. Maturity of the lungs - surfactant
placental development
The placenta develops after the 3rd week of gestation
At term it will weigh 1- 1 ½ lbs.
It develops from the trophoblast layer(chorion) of the blastocyst and the layer of maternal endometrial that lies directly under the developing ovum
(Decidua basalis)
need at least how many pounds of weight gain
25 lbs, if less than deriving the baby; denial then don’t gain weight because don’t want to show it (teenage pregnancy)
deoxygenated blood and waste will seep out of
chorionic villi to be disposed of
in baby veins carry and arteries carry
oxygenated blood and arteries deoxygenated blood
Two types of Chorion
- Chorionic villus- villa that tap into pools of maternal blood that are formed in the decidua basalis, this will be the fetal portion of the future placenta and supply O2 and nutrients to the fetus
- Chorionic plate - some of the villa die and are pushed downward and it forms part of the tissue that becomes the fetal membranes
fetal side of placenta
smooth and glistening
If placenta separates from the middle this side (shiny Schultz) will deliver up in 80% of cases
maternal side of placenta
red and fleshlike,
has individual cotyledons that each contain a spiral artery (villus)
As the placenta ages these sites infarct but only need 50% for adequate perfusion
This side is delivered up when separation begins around the edges, in 20%of deliveries
if maternal side up of placenta then
dirty ucan
placenta functions
- Production of hormones
HUMAN CHORIONIC GONADOTROPIN (HCG) will stimulate the continued release of progesterone and estrogen so menses will not occur and uterine contractibility is decreased
Also HUMAN PLACENTAL LACTOSE (growth hormone)
2. Transports gases (acts as the lungs)
so fetal blood doesn’t go to lungs
3. Transport of nutrients (GI system)
4. Excreation of wastes (kidney)
5. Conjugation of drugs and hormones (liver)
look for HGH in pregnancy test in
urine;
tells body not to shed tissue so placenta can develop;
starts 2nd week
if pregnancy test at 22 wks won’t have high enough HGH levels to test positive
fetal membranes
The fetal membranes will be made up of the CHORION (which came from the chorionic plate) and the AMNION which is an outgrowth of tissue from the placenta
The membranes holds the fetus suspended in
amniotic fluid
amniotic fluid
Cushioning the fetus
Helps to maintain a constant temperature
Keeps the membranes from adhering to the fetus
Allows movement of fetus and muscle development
The fluid comes from fetal urine and maternal blood across the amnion
-98% of fluid is water
-don’t want meconium
-if diabetic mother than can have polychyctamnios
umbilical cord
Two arteries- carries deoxygenated blood
One vein - carries oxygenated blood
Lack of a vessel can indicate congenital abnormalities
Wharton’s jelly - soft, spongy substance covering the umbilical cord
fetal circulation extra structures
- Ductus venous (liver)- connects the umbilical vein and the inferior vena cava
- Foramen Ovale- opening between the right and left atrium
- Ductus arterious- shunts blood to aorta and away from the lungs
fetal circulation
when baby is stressed in utero, blood is shunted to brain and heart
when cord clamp readjustment of pressures
transiet murmor -
foramen ovale doesn’t completely close except murmur to go away at some point
monozygotic twins-
1 placenta, identical twins, always the same sex, can have conjoined twins
dizygotic twins-
can be different sexes, with two placentas, each fertilized by multiple sperm
ovum and sperm —>
zygote
zygote —>
morula (at 16 cells)
morula —>
blastocyst
blastocyst —>
trophoblast and embryoblast
