Placenta

Question 1

What is the placenta?

Answer 1

Primary site of nutrient and gas exchange between mother and fetus

Question 2

Cytotrophoblast

Answer 2

Inner layer of chorionic villi

Question 3

Syncytiotrophoblast

Answer 3

outer layer of chorionic villi

Question 4

Trophoblastic layer of cells in the blastocyst is basically what?

Answer 4

Placental stem cells

Question 5

Implantation takes place on what day

Answer 5

6-7

Question 6

hCG is a product of

Answer 6

the placenta and more specifically, trophoblast cells

Question 7

What is the system responsible for the rolling of the blastocyst along the endometrium prior to implantation?

Answer 7

L-selectin system

Question 8

Describe the L-selecting system

Answer 8

ok…
SO the blastocyst expresses the L-selectin
- this allows the blastocyst to weakly interact with the glycocalyx which lines the endometrial surface
and then BOOM—– hCG is secreted by the trophoblast cells of the blastocyst

Question 9

What does hCG do to the endometrium

Answer 9

It stimulates the upregulation of TROPHININ on endometrial epithelial cells. This trophinin contain pnipodes. The blastocyst then strongly binds to the endometrial surface via the trophonin trophonin binding.

Question 10

So hCG

Answer 10

stimulates the growth of pinopodia on the endometrium

Question 11

What is decidualisation?

Answer 11

It is the increase in vascular permeability and secretory activity of stromal cells in the endometrium. It really is the response of the maternal cells to progesterone

Question 12

What stimulates decidualisation?

Answer 12

Attachment….this hCG initiate process

Question 13

LIF and EGF

Answer 13

signals that come from the endometrial stromal cells

Question 14

KNOW

Answer 14

Decidual reaction occurs in very early pregnancy. Appears in the area where the blastocyst contacts teh endometrial decidua. Consists of an increase in secretory functions of the endometrium.

Question 15

Invasion

Answer 15

• Within hours of attachment trophoblasts destroy epithelial cells
• Some trophoblast cells fuse and become syncytiotrophoblast
• Other trophoblast cells retain their cellularity (cytotrophoblasts)
• Finger like outgrowths called villi invade the decidua and attack blood vessels
• The villi are then invaded by embryonic blood vessels

Question 16

When does this invasion occur>

Answer 16

first 2-3 weeks of gestation

Question 17

Describe the syncytiotrophoblast

Answer 17

multinucleated, no cell boundaries

• invades the endometrial stroma
• Major source of hormone production, particularly hCG

Question 18

So, realize that the chorionic villi is made up of the syncytiotrophoblast and the cytotrophoblast.

Answer 18

The chorionic villi is what invades the decidua

Question 19

The arrangement of embryo surrounded by cytotrophoblast, syncytiotrophoblast, and maternal tissue remains the paradigm throughout gestation

Answer 19

ok

Question 20

Remember, what is the most important job of the syncytiotrophoblast

Answer 20

secretes hCG which stimulates the corpus luteum to make progesterone during the first trimester

Question 21

At what point during gestation is a vascular network established in the placenta with facilitates maternal-embryonic exchanges of gases, nutrients, and metabolic waste products

Answer 21

end of fourth week

Question 22

secondary chorionic villi>

Answer 22

Early in the third week of gestation, mesenchymal tissue invades the primary chorionic villi and this forms secondary chorionic villi

Question 23

Secondary chorionic villi cover….

Answer 23

the entire chorionic sac

Question 24

chorionic villi cover the entire chorionic sac until when>

Answer 24

week 8 when the villi begin to be compressed. This reduces the blood supply to the villi and eventually the degenerate producing a relatively avascular area

Question 25

What is this avascular area which succeedes the chorionic villi called?

Answer 25

smooth chorion

Question 26

KNOW: Spiral arteries do not have a muscular layer which makes them very low resistance. You must have a ton of blood going to the fetus in order to make it develop, you need very low resistance vessels

Answer 26

In order to make make the spiral arteries good enough for this task, they must be remodeled.

Question 27

What are the two mechanisms of spiral artery remodelling?

Answer 27

• interstitial
• intravascular
  KNOW

Question 28

Pre-eclampsia is caused by

Answer 28

faulty trophoblast invasion during pregnancy. Leads to high resistance in the spiral arteries and can cause IUGR

Question 29

Pre-eclampsia is

Answer 29

HTN, PROTEINURIA, EDEMA