T6-Placentation

Question 1

Fetal component of Placenta

Answer 1

chorion frondosum

Question 2

Maternal component of placenta

Answer 2

decidua basalis

Question 3

Formation of Chorionic Villi

Step 1

Answer 3

days 12-13, cells of cytotrophoblast proliferate and penetrate syncytiotrophoblast creating primary villi

Question 4

Formation of Chorionic Villi

Step 2

Answer 4

days 13-15, core of primary villi is invaded by extraembryonic somatic mesoderm creating secondary villi

Question 5

Formation of Chorionic Villi

Step 3

Answer 5

days 18-22, mesoderm in the villus core differentiates into blood vessels creating teritary villi

Question 6

The Chorion refers collectivly to what structures

Answer 6

extraembryonic somatic mesoderm, cytotrophoblast, syncytiotrophoblast

Question 7

Placenta=

Answer 7

decidua basalis+ chorion frondosum

Question 8

Oxygenated ______blood leaves______arteries and freely flows through ______________ (previously called lacunar networks) bathing the surface of each ________

Answer 8

maternal; spiral; intervillous spaces; villus

Question 9

Deoxygenated maternal blood is removed by what

Answer 9

open uterine veins

Question 10

Until about 20 weeks placental membrane is formed by

Answer 10

syncytiotrophoblast, cytotrophoblast, extraembryonic mesoderm, embryonic endothelium

Question 11

Placental membrane

Answer 11

separates maternal blood from fetal blood

Question 12

After about 20 weeks placental membrane is formed by

Answer 12

syncytiotrophoblast, endothelium, and a sometimes absent extraembryonic mesoderm

Question 13

Cotyledons

Answer 13

placental lobes separated from each other by placental septa

Question 14

Where is the umbillical cord attached

Answer 14

center of the placenta

Question 15

What does the umbillical cord consist of

Answer 15

Two umbillical arteries, one umbillical vein, mucoid CT on maternal side

Question 16

Dizygotic twins

Answer 16

ovulation and fertilization of two oocytes; each twin has its own amniotic cavity

Question 17

Monozygotic twins

Answer 17

splitting of zygote ate various stages of development

Question 18

Twin transfusion syndrome

% occurance rate

Answer 18

10-15% diamniotic twins

Question 19

Twin transfusion syndrome

how it happens

Answer 19

Fused placenta anastomoeses occur between two placental circulatory systems.

Question 20

Twin transfusion syndrome result

Answer 20

donor twin that is small and pale and recipient twin is large with polycythemia

Question 21

Fate of the Amniotic Cavity

Answer 21

• Persists throughought pregnancy surrounding growing embryo
• Encases the umbillical cord
• Pushes overtop of fetal surface of placenta
• Eventually the amnion fuses with inner chorion

Question 22

Fusion of amnion with inner chorion results in

Answer 22

oblitteration of the chorionic cavity and formation of the amniochorionic membrane

Question 23

Fate of the Chorionic Cavity

Answer 23

Growth of the embryo and expansion of the amniotic cavity results in reduction of the chorionic cavity

Question 24

Fate of the Umbillicall vessicle

Answer 24

• shrinks with time

- naturally atrophies as pregnancy progresses

Question 25

Fate of the Uterine Cavity

Answer 25

reduction of uterine cavity as the fetus grows and fusion of the decidua capsularis with the parietalis

Question 26

What is placental accreta

Answer 26

abnormal adherence of chorionic villi to myometrium

Question 27

What is placental previa

Answer 27

low placental location that partially or fully covers the internal os

Question 28

What is placenta percreta

Answer 28

Penetration of chorinic villi through the full thickness of the myometrium