OB Ch 56 Placenta

what is the main purpose of placenta

to exchange of oxygenated maternal blood w/deoxygenated fetal blood

what do the (2) UA’s carry

deoxygenated blood from fetus to placenta

when does implantaion occur

6-7 days after fertilization

what are the two types of trophoblastic cells

syncytiotrophoblast (outer layer) and cytotrophoblast (inner layer)

where is a reaction that occurs between the blastocyst and myometrium

decidua basalis (implantation side closest to mom)

what is the reaction occuring over blastocyst closest to endo cavity

decuda capsularis

what is the reaction except for areas above and below implantation - opposite side

decidua vera (parietalis)

what are the two components of the placenta

maternal=decidua basalis (from endo surface-basal plate) and fetal from chorion frondosum (chorionic plate)

what is the fetal portion of the placenta

chorion frondosum - has villi

what is the maternal portion of the placenta

chorion leave - nonvillous around gestational sac

what plate(s) are the fetal surface and maternal surface called

chorionic (fetal), basal (maternal)

what is major functioning part of placenta

chorioinic villus

what secures fetal placenta to maternal placenta

cytotrophoblastic shell and anchoring villi

villi connected to the decidual basalis through cytotrophoblastic shell are called

anchoring villi

what are villi growing from stems of side villi called

branch villi

functions of placenta

respiration, excretion, hormones, nutrition, protection, storage

what trophoblasts produce hormones

syncytiotrophoblasts

what hormones do syncytiotrophoblasts produce

hCG, estrogen, progesterone, human placental lactogen (hPL)

what structure bypasses fetal lungs

ductus arteriosis

what structure bypasses fetal liver

ductus venosus (to IVC, to RA)

what is it called when the cord is attached <2 cm from edge

marginal insertion, battledore placenta

what is the term when the cord inserts into fetal membrane

velamentous

what is it called when placental implantation occurs in lower uterine segment

placenta previa (if covering cervix) or low-lying placenta (>2 cm from os)

what are the fetal membranes

chorion, amnion, allantois, YS

when does the amnion develop

28th menstrual day, attached to embryionic disc - becomes umbilicus

when should fusion of amnion and chorion happen

by 16 gestational weeks

when and where does secondary YS happen

ventral surface of embryonic disc by 4 menstrual weeks

when does the umbilical cord form

in first 5 weeks of gestation

when do intestines herniate into UC

7 weeks

when should intestines be completely retracted by

12 weeks

what is omphalocele

ab organs within cord and protrude outside ab wall

what is gastrochisis

congenital fissure in ab wall to right of cord, bowel or other organs may protrude outside

what does the ductus venosus become after birth

ligamentum venosum

where do the UA arise from

internal iliac arteries

what is normal position of UA

around fetal bladder

______ to ______ % of two vessel cord have malformations

25-50%

who is more susceptible to 2VC

diabetic mothers and twins

what is sono of fetal surface of placenta

echogenic chorionic plate along placental tissue found at junction/adjacent to amniotic fluid

what is sono of maternal portion of placenta

junction of myometrium and substance of placenta

what vasculature is often confused with placental abruption

maternal blood vessels from the endo that run behind the basal plate

what placental position will cause the endo veins to be more prominent

fundus of posterior of uterine cavity

when can you identify appearance of placenta

8 weeks

until what week will placenta appear smooth

20 weeks

what placental thickness is typical >23 weeks

2-3 cm

what placental thickness is abnormal

>4 cm

what are cystic structures behind the chorionic plate and between amnion and chorion layers

large fetal vessels

what are some methods to viewing the os

tilting patient to slight trendelelburg, endovag, transperineal

what is the (incorrect) term used for placental position changes

migrate

what resistance is UA in 1st trimester

high w/notched appearance

what resistance is UA in 2nd trimester

low resistance - no more notchingby 24 weeks

what causes waveform to become low resistance in 2nd trim

invasion of spiral arteries

what size does placenta measure and weigh at delivery

15-20 cm diameter, 600 g

what ratio of pregnancies will have placenta previa

1:200

where does placenta typically implant

body or fundus of UT

what is it called when fetal vessels run across cervical os

vasa previa

what are the most common causes of vasa previa

velamentous cord, a succenturiate lobe (accessory placenta lobe)

what is it called when the placenta adheres to myom rather than decidua

morbidly adherent placenta

what are 3 types of morbidly adherent placenta

accreta, increta, percreta

what does placenta accreta mean

across, superficial - chorionic villi attach to myom. without muscle invasion

what does placenta increta mean

deep, invade, through - chorionic villi into myometrium

what does placenta percreta mean

passes through (per-) - come through other side of wall, may affect bladder

most cases of morbidly adherent placenta occur in what type of previa

anterior placenta previa and Hx of C-section

what is ratio of placenta accreta

1:2500

what is it called when placental membranes attach to fetal surface of placenta rather than the underlying villus placental margin - it is not covered by chorionic plate

circumvallate/circummarginate placenta

what is the difference between circumvallate and circummarginate

placental margin is folded, thickened, or elevated w/fibrin and hemorrhage in circumvallate, circummarginate is outside of chorionic plate but not folded

what is ratio of placental abruption

1:120

where does bleeding occur in placental abruption

decidua basalis

where is a retroplacental abruption

between UT and placenta

what is retroplacental abruption associated with

HTN, vascular disease - high pressure bleed

where does retroplacental abruption stem from

spiral arteries

what is most common type of abruption

marginal - low pressure bleed

what is marginal abruption also called

subchorionic hemorhhage

where does marginal abruption stem from

marginal veinsa

what is ratio of intervillous thrombosis

1/3 - little risk

what is intervillus thrombosis associated with

RH sensitivity and elevated AFP

what is most common tumor of placenta

trophoblastic disease

what are gestational trophoblastic diseases also called

molar pregnancy

what is associated with gest tropho disease

theca lutein cysts - can be B or M

what is 2nd most common benign vasular tumor of placenta

chorioangioma