13_Devo Block 4.2 The Placenta

Front 1

The placenta is a fusion between what two tissues?

Back 1

Fetal (chorion) and Maternal (endometrial)

Front 2

The diameter of the placenta:
The thickness:
Surface area
Weight

Back 2

15-20 cm in diameter
2-3 cm thick
500-600 g
10 square meters

Front 3

When does implantation occur

Back 3

Between wk 1 and 2 of development

Front 4

What is the status of the uterine endometrium during implantation?

Back 4

Its in the secretory phase (day 14-26 of cycle).

Front 5

The "Implantation window" occurs between day ? and ? of the cycle when ?? is the dominant hormone.

Back 5

Between 19-21 and Progesterone

Front 6

What is the status of the embryo during implantation (draw it)? What does it interact with?

Back 6

Blastocyst stage. The trophoblast tissue of the blastocyst interacts with the "primed endometrium"

Front 7

The outer layer of epithelium of the blastocyst is called:
The internal cluster of non-polarized cells is called the:
The fluid filled lumen is called:

Back 7

Trophoblast
Inner Cell mass
Blastocyst cavity

Front 8

What tissue mediates the implantation processes?

Back 8

Trophoblast

Front 9

What happens as soon as the trophoblast makes contact with the endometrium?

Back 9

It begins to proliferate.

Front 10

AS the trophoblast proliferates upon contact with the endometrium, it forms a new layer of cells called:
Describe its cellular morphology.

Back 10

Syncytiotrophoblast - it has multiple nuclei but no cell-cell borders. Microvilli on the expanding ST plasma membrane increase the are for transport.

Front 11

The endometrium is divided into two areas:

Back 11

Functional Zone (outer 2/3) = menstral flow
Basal Zone (inner 1/3) = does not flow but generates a new endometrium

Front 12

When do the lecuni form? And what do they eventually form and fill up with?

Back 12

Day 9. They grow and encounter the uterine glands and uterine capillaries within the functional zone of the endometrium and the contents of those structures begin to empty into lecuni.

Front 13

When is the embroy completely embedded in the endometrium?

Back 13

Day 12-14

Front 14

What does the inner cell mass produce?

Back 14

Yolk sac, bilaminar disc, amnion

Front 15

After the trophoblast fuses with the endometrium and syncytiotrophoblast forms, the original trophoblast remains cellular and is know as:
What does it do?

Back 15

Cytotrophoblast. It continues to make syncytiotrophoblast

Front 16

Label

Back 16

Red: Chorionic Plate
Blue: Cytotrophoblastic Shell

Front 17

What does the syncytiotrophoblast secrete? At about day ?
When does this peak?
What does it stimulate?

Back 17

hCG at about day 7.
levels peak at week 8
hCG stimulates testosterone production in the embryonic testis

Front 18

The trophoblast and associated extraembryonic mesoderm (EEM) is called Chorionic Plate. Describe what these vessels anastomose with:

Back 18

They anastomose with those vessels forming within the body stalk and eventually those forming within the embryo - thus nutrients from maternal blood within the lucunar network can diffuse into vascular chorionic plate and gain access to the embryo.

Front 19

What is the reaction called that is stimulated by implantation of the embryo into the endometrium?

Back 19

The Decidual Rxn

Front 20

hCG supports this tissue:
Also stimulates:

Back 20

Supports Corpus Luteum in the ovary
Stimulates testes to produce testosterone.

Front 21

Where does the Decidual Rxn take place?

Back 21

Throughout the ENTIRE function layer of the endometrium of the uterus.

Front 22

What happens during the Decidual Rxn? What two things might it prevent?

Back 22

The endometrial glands & stromal cells enlarge and become filled with glycogen & lipid. It may prevent uncontrolled invasion of the trophoblast and/or immunological attack by mother's immune system.

Front 23

To protect the embryo from immune attack, what two things happen? (one from maternal and one from embryo)

Back 23

1. Leucocytes infiltrating the endometrial strom secrete interlukin 2 to prevent maternal recognition of embryo as foreign.
2. Embryo may produce immunosuppressive cytokines or proteins.

Front 24

As you know, the ENTIRE endometrium undergoes the decidual rxn and becomes know as the "Decidua". What are the different regions of the decidua called with respect to the position of the embryo?

Back 24

1. Dedidua Basalis = site of implantation
2. Decidua Capsularis = decidua over top of the embryo
3. Decidua Paretalis = remainder of deciduating endometrium

Front 25

The uterine myometrium is tough and it would be a challenge for the embryo to grow there. It needs to relax. How is this achieved? (Hint: 1st one tissue produces the hormones, 2nd a different tissue produces the hormones)

Back 25

Progegesterone quiets the contractility of the myometrium and estrogen proliferates the smooth muscle cells - in effect causing both hypertophy and hyperplasia. The progesterone and estrogen are first produced by the Corpus Luteum and then by the placenta

Front 26

Define the chorion:

Back 26

The trophoblast [cytotrohoblast & syncytiotrophoblast] + Extraembryonic mesoderm

Front 27

There are three phases of Chorinonic Villi formation - what are they and when do they occuer?

Back 27

1. Primary between d11-14
2. Secondary between d16-20
3. Tertiary between d21-birth

Front 28

Describe the primary stage of chorionic villi formation.

Back 28

Cytotrophoblast cells within the decidua basalis and capsularis cells proliferate locally and grow into syncytiotrophoblast. These are the primary chorionic villi

Front 29

Describe the secondary stage of chorionic villi formation.

Back 29

Extraembryonic mesoderm forms a core within the primary villi transforming them into Secondary Villi

Front 30

Describe the Tertiary stage of chorionic villi formation.

Back 30

Vascular plexus forms within the mesoderm core transforming the secondary villi into Tertiary villi by the end of week three. Vessels within the tertiary villi anastomose with vessels forming in the chrionic plate which in turn anastomose with vessels forming in the body stalk.

Front 31

What are the three parts of the Tertiary Chorionic Villi

Back 31

1. Stem (anchoring) villi (trunk)
2. Intermediate (free) villi (branch)
3. Terminal villi (leafs)
**Each region has specific functions and circulatory patterns

Front 32

The Intermedia Villus is flowing in what? What are the vessels called here?

Back 32

Lakes of maternal blood. Arterioles and venules

Front 33

What provides the main support of the Villous Tree? How? (see p5)

Back 33

The Stem Villi is anchored in the adjacent decidua. What happens is a column of cytotrophoblast will extend distally through the syncytiotrophoblast and expand adjacent to the dicidua contributing to the cytotrophoblastic shell

Front 34

What is contained in the Terminal Villi? What happens here>?

Back 34

Dialated capillary loops called sinusoids. Nutrient exchange between baby and mother.

Front 35

The placenta must detach at partuition. What is this akin to?

Back 35

Menstural flow.

Front 36

In preparation for partuition, the placenta creates an interface with the maternal side know as:
And the fetal side known as:

Back 36

Maternal = Basal Base
Fetal = Placental Base

Front 37

The Basal Base consists of: P6

Back 37

Functional layer of endometrium in the are of the decidua basalis that is coated with cyto- and syncytiotrophoblast (i.e. the cytotrophoblastic shell)

Front 38

The Basal Base consists of: (p6, 34:05 lecture)

Back 38

Basal zone of the endometrium and stays in the uterus after birth.

Front 39

During the 2nd and 3rd month, what happens to the villi associated with the decidua capsularis? What is left behind?

Back 39

It atrophies leaving behind a smooth surfaced chorion called Chorion Laeve [laeve=smooth]

Front 40

During the 2nd and 3rd month, the decidua basalis retains its chorionic villi and becomes known as:

Back 40

Chorion Frondosom [frondosom = bushy, leafy]

Front 41

The placenta as we know it is the junction between the:

Back 41

Chorion Frondosum (villi) and Decidua Basalis (surrounding tissue of maternal blood, etc)

Front 42

What is the fate of the Desidua Laeve?
What is the fate of the Desidua Parietalis

Back 42

1. It eventually disappears
2. Fuses with embryonic membrane

Front 43

Name A and B. **What are the individual leafy parts called and what does it contain?

Back 43

A = Chorion Laeve
B = Chorion Frondosum (where placenta is forming)
**Condyledons containing mature tertiary villi

Front 44

This is what the mature placental circulation looks like.
1. What is lime green area?
2. What is B pointing to?
3. What space is B going into?
4. What is the Tree-like vessel projecting into the space? What is it bathed in?
5. What is A pointing to?
6. What tissue surrounds the tree and surface of the placenta septa?

Back 44

1. Desidua basalis
2. Endometrial Artery and Vein
3. Intervillous spaces
4. Mature tertiary villus bathed in maternal blood
5. Cytotrophoblastic column anchor
6. Syncytiotrophoblast

Front 45

This is the Initial Placental Barrier. Label
1. The outer pink cells
2. The inner Blue cells
3. Bolender's blue line cells
4. Bolender's blue line/pink inside cells
5. Bolender's cells circled in blue in middle.

Back 45

1. Syncytiotrophoblast
2. Cytotrophoblast
3. Basement Membrane
4. Extraembryonic Mesoderm
5. Capillary Endothelium

Front 46

This is placenta after Month 4. What do you notice compared to the Initial Placental Membrane?

Back 46

1. There is loss of cytotrophoblast
2. There is thinning of syncytiotrophoblast

Front 47

What are the three main functions of the Placenta?

Back 47

1. Mediates transport & metabolism of nutrients/wastes
2. Secretes essential proteins & hormones
3. Protects the embryo/fetus from immunological attack

Front 48

Give examples of what the three major methods by which materials cross the placental barrier?

Back 48

1. Diffusion - eg gases, drugs, steroids
2. Endocytosis - Abs, disease agents
3. Exocytosis - metabolic waste, hormones

Front 49

What type of steroids does the placenta produce?

Back 49

Estrogens

Front 50

Since fetus is an allograph, it needs to be protected from mothers immune system. What are the three possibilities by which it does this?

Back 50

1. Surface of syncytiotrophoblast has no paternal histocompatibility
2. Maternal immune system is selectively suppressed
3. Decidual rxn sets up immunological privileged site for embryo/fetus "an allograph safe house"

Front 51

What is the fetal side of the placenta called? What is it covered by and what can be seen through it?

Back 51

The shiny side covered with chorioanmiotic membrane through which chorionic vessels are visible.

Front 52

What is the maternal side of the placenta called? It is distinguished by the presence of 15-20:

Back 52

The muddy side distinguished by Placental Cotyledons (hypertrophied tertiary chorionic villus)

Front 53

What is the area between cotyledons called?

Back 53

Placental Septae (see that one amazing diagram in a previous nc)

Front 54

Why must the placenta be examined to assure that all placental cotyledons are intact?

Back 54

If left behind, can cause choriocarcinomas.

Front 55

This abnormal development may cause tearing of the placental attachment and hemorrhage primarily in the third trimester.

Back 55

Placenta Previa

Front 56

In Placenta Previa, implantation usually happens:
Severity depends on whether attachment:

Back 56

-too near the cervix;
-severity dependent on whether placental attachment completely, partially or marginally covers the cervix

Front 57

Why does implantation near the cervix cause a problem>

Back 57

Bc the cervix does not undergo the decidual rxn and thus implantation is not secure at this site and is easier to disrupt.

Front 58

In this condition, implantation extends into the basal zone of the endometrium:

Back 58

Placenta Accreta

Front 59

What causes the problem in Placenta Accreta? What may be required?

Back 59

It's difficult to remove all of the placenta during delivery. Hysterectomy may be required.

Front 60

If implantation extends into myometrium:

Back 60

Placenta Increta

Front 61

If implantation extends into uterine serosa or other organ:

Back 61

Placenta Percreta

Front 62

Detachment of the placenta before birth:
What might cause this?

Back 62

-Placental Abruption
-May be caused by initial hemorrhage into the decidua basalis causing a split in the junctional layer

Front 63

What abusive drug may cause Placental Abruption?

Back 63

Cocaine

Front 64

If the embryo doesn't develop but the trophoblast development continues, resulting in a multicystic, intrauterine mass, it's called:
Complete vs Incomplete?

Back 64

Hydatidiform Mole
Complete = only paternally derived DNA present and can transform into malignant condition (caused by dispermy); In Incomplete, the development depends on the ration between paternal and maternal DNA present in the conceptus - not malignant

Front 65

In this condition, the umbilical cord attaches to the chorion and amnion rather than the placenta:

Back 65

Velamentous Cord Insertion