T6-Placentation Flashcards
Fetal component of Placenta
chorion frondosum
Maternal component of placenta
decidua basalis
Formation of Chorionic Villi
Step 1
days 12-13, cells of cytotrophoblast proliferate and penetrate syncytiotrophoblast creating primary villi
Formation of Chorionic Villi
Step 2
days 13-15, core of primary villi is invaded by extraembryonic somatic mesoderm creating secondary villi
Formation of Chorionic Villi
Step 3
days 18-22, mesoderm in the villus core differentiates into blood vessels creating teritary villi
The Chorion refers collectivly to what structures
extraembryonic somatic mesoderm, cytotrophoblast, syncytiotrophoblast
Placenta=
decidua basalis+ chorion frondosum
Oxygenated ______blood leaves______arteries and freely flows through ______________ (previously called lacunar networks) bathing the surface of each ________
maternal; spiral; intervillous spaces; villus
Deoxygenated maternal blood is removed by what
open uterine veins
Until about 20 weeks placental membrane is formed by
syncytiotrophoblast, cytotrophoblast, extraembryonic mesoderm, embryonic endothelium
Placental membrane
separates maternal blood from fetal blood
After about 20 weeks placental membrane is formed by
syncytiotrophoblast, endothelium, and a sometimes absent extraembryonic mesoderm
Cotyledons
placental lobes separated from each other by placental septa
Where is the umbillical cord attached
center of the placenta
What does the umbillical cord consist of
Two umbillical arteries, one umbillical vein, mucoid CT on maternal side
Dizygotic twins
ovulation and fertilization of two oocytes; each twin has its own amniotic cavity
Monozygotic twins
splitting of zygote ate various stages of development
Twin transfusion syndrome
% occurance rate
10-15% diamniotic twins
Twin transfusion syndrome
how it happens
Fused placenta anastomoeses occur between two placental circulatory systems.
Twin transfusion syndrome result
donor twin that is small and pale and recipient twin is large with polycythemia
Fate of the Amniotic Cavity
- Persists throughought pregnancy surrounding growing embryo
- Encases the umbillical cord
- Pushes overtop of fetal surface of placenta
- Eventually the amnion fuses with inner chorion
Fusion of amnion with inner chorion results in
oblitteration of the chorionic cavity and formation of the amniochorionic membrane
Fate of the Chorionic Cavity
Growth of the embryo and expansion of the amniotic cavity results in reduction of the chorionic cavity
Fate of the Umbillicall vessicle
- shrinks with time
- naturally atrophies as pregnancy progresses
Fate of the Uterine Cavity
reduction of uterine cavity as the fetus grows and fusion of the decidua capsularis with the parietalis
What is placental accreta
abnormal adherence of chorionic villi to myometrium
What is placental previa
low placental location that partially or fully covers the internal os
What is placenta percreta
Penetration of chorinic villi through the full thickness of the myometrium
