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Question 1

What are the 5 stages of early embryonic development all the way from ovulation?

Answer 1

1 Ovulation

2 fertlization

3 Cleavage

4 blastulation

5 Implantation

Question 2

What happens during ovulation?

Answer 2

A secondary oocyte is released surrounded by zona pellucida and granulosa cells.

Question 3

: What occurs during fertilization?

Answer 3

A: A sperm enters the secondary oocyte, resulting in a zygote.

Question 4

Q: What happens during the cleavage stage?

Answer 4

A: The zygote undergoes rapid mitotic divisions, increasing from 2 blastomeres to 16 blastomeres (forming a morula).

Question 5

Q: What happens during the blastulation stage?

Answer 5

A: The formation of a blastocyst—a hollow ball of cells with a central cavity and has an outer layer known as the tropoblast

Question 6

What does the trophoblast form?

Answer 6

The placenta

Question 7

What do the inner mass cells form?

Answer 7

These will develop into the actual embryo.

Question 8

At what stage does the zona pellicuda disappear?

Answer 8

blastulation- the blastocyst does not have a zona pellicuda

Question 9

: What happens during implantation?

Answer 9

A: The blastocyst attaches to the uterine lining (endometrium) and the polar trophoblast invades it.

Question 10

What are the two layers that trophoblasts differentiate into during the lacunar stage?

Answer 10

1. Cytotrophoblasts (CTs) 2. Syncytiotrophoblasts (STs).

Question 11

What characterizes cytotrophoblasts (CTs)?

Answer 11

They are mononuclear cells located in the inner layer and appear beige.

Question 12

What distinguishes syncytiotrophoblasts (STs)?

Answer 12

They are multinucleated, form an outer layer, and have finger-like projections into the endometrium, appearing pink.

Question 13

What are the three functions of the syncytiotrophoblast?

Answer 13

Lyctic activity where uterine tissue is broken down to form lacunae

Erosion of Maternal Capillaries

extend finger-like projections into the endometrium to facilitate nutrient uptake

Question 14

Q: What hormone does the syncytiotrophoblast secrete, and why is it important?

Answer 14

A: Human chorionic gonadotropin (hCG); it signals the presence of the embryo and is detected in pregnancy tests.

Question 15

: What fills the blastocyst cavity, and what is its significance?

Answer 15

A: It is filled with extraembryonic mesoderm, which supports the embryo and facilitates nutrient transfer.A: It is filled with extraembryonic mesoderm, which supports the embryo and facilitates nutrient transfer.

Question 16

What is the extraembryonic coelom?

Answer 16

A cavity within the extraembryonic mesoderm that plays a role in early placental development.

Question 17

What happens to the extraembryonic mesoderm during the Primary Chorionic Villi Stage?

Answer 17

It shrinks and organizes next to the cytotrophoblasts (CTs).

Question 18

How is the embryo attached to the cytotrophoblasts (CTs)?

Answer 18

Through a stalk of extraembryonic mesoderm.

Question 19

What are the three layers of the chorion?

Answer 19

1. Extraembryonic Mesoderm (Dark Purple)
2. Cytotrophoblasts (CTs) (Beige)
3. Syncytiotrophoblasts (STs) (Pink)

Question 20

What composes the primary chorionic villi?

Answer 20

Columns made entirely of cytotrophoblasts (CTs).

Question 21

What is the chorion?

Answer 21

Fetal portion of the placenta.

Question 22

What are the two main layers of the secondary chorionic villi?

Answer 22

1. Cytotrophoblasts (beige) 2. Extraembryonic mesoderm (purple)

Question 23

What happens to the extraembryonic mesoderm during the Secondary Chorionic Villi Stage?

Answer 23

It invaginates (pushes) into the chorion.

Question 24

What significant development occurs during the Tertiary Chorionic Villi Stage?

Answer 24

The umbilical artery and vein grow into the mesoderm and vascular villi form.

Question 25

What are the four layers present in the tertiary chorionic villi?

Answer 25

1. Syncytiotrophoblast (Pink) 2. Cytotrophoblasts (Beige) 3. Mesoderm (Purple) 4. Umbilical Capillaries

Question 26

At what stage do vascular villi appear?

Answer 26

Tertiary chorionic villi stage.

Question 28

What are the two types of villi present during the Tertiary chorionic Villi Stage?

Answer 28

1. Stem (anchoring) villi 2. Branch villi

Question 29

What is the purpose of branch villi?

Answer 29

They extend into the lacunae to facilitate nutrient and gas exchange with maternal blood.

Question 30

What happens to the barrier between maternal and fetal blood at this stage?

Answer 30

The barrier gets thinner, enhancing nutrient and gas exchange.

Question 31

What are the 6 layers of the diffusion barier between the fetus and the mother?

Answer 31

Oxygen from mom to baby: 1. Syncytiotrophoblast (pink) ↓ 2. Cytotrophoblast (beige) ↓ 3. Basement membrane of both trophoblasts (not on image) Two trophoblasts are sharing one basement membrane ↓ 4. Mesenchyme core (purple) ↓ 5. Basement membrane of endothelium of fetal umbilical capillaries ↓ 6. Endothelium of fetal umbilical capillary

Question 32

What happens to the basement membrane of the syncytiotrophoblast and cytotrophoblast as the mesenchyme shrinks?

Answer 32

As the mesenchyme core shrinks: The 2 basement membranes will fuse

Question 33

At what stage does the mesoderm appear?

Answer 33

Secondary chrionic villi stage

Question 34

In which week does the **primary** chrionic villi stage take place

Answer 34

13–15 days (week 2)

Question 35

In which week does the **Secondary** chrionic villi stage take place

Answer 35

16–21 days (week 3)

Question 36

In which week does the **Tertary** chrionic villi stage take place

Answer 36

22-28 days (week 4)

Question 37

In which of development is the placenta completed?

Answer 37

Week 6-Month 4

Question 38

Where do the umbilical arteries arise from in the fetus?

Answer 38

The two internal iliac arteries.

Question 39

What is the primary function of the umbilical arteries?

Answer 39

To carry blood away from the heart of the fetus towards the placental umbilical capillaries for gas exchange.

Question 40

Where does the umbilical vein start?

Answer 40

At the umbilical capillaries of the fetus.

Question 41

What are the branches of the umbilical vein?

Answer 41

One branch goes to the liver and one to the inferior vena cava.

Question 42

What are those two structures?

Answer 42

**LEft:**Early Placenta: 6 weeks, 40x, HE **Right:** Term Placenta: 40x, HE

Question 43

What are those two structures?

Answer 43

**L** Early Placenta: 6 weeks, 100x, HE **R** Term Placenta: 100x, HE CTs (C) atrophied (from 4th month()

Question 44

What is this?

Answer 44

Question 45

What are the three layers of the diffusion barrier of a mature placenta?

Answer 45

Diffusion Barrier: 3 layers: Syncytiotrophoblast (ST) Fused basement membrane (F) Endothelium of umbilical capillaries (C)

Question 46

What is the Chorion Frondosum?

Answer 46

The part of the chorion that is covered in villi and involved in gas and nutrient exchange.

Question 47

What is the Decidua Basalis?

Answer 47

It forms the maternal side of the placenta and connects maternal blood supply to fetal blood supply.

Question 48

What does the Decidua Parietalis line?

Answer 48

It lines the myometrium (the muscular layer of the uterus) and the inner surface of the uterus.

Question 49

Is the Decidua Parietalis part of the placenta?

Answer 49

No, it is not part of the placenta.

Question 50

What is the Decidua Capsularis?

Answer 50

A layer that surrounds the developing embryo and is in direct contact with the uterine cavity.

Question 51

Where is the Decidua basalis, Decidua capsularis, and Decidua parietalis located?

Answer 51

**Decidua basalis**: under embryo (maternal placenta) **Decidua capsularis:** between embryo and uterine cavity **Decidua parietalis**: between myometrium and uterine cavity

Question 52

What is this and what does it contain?

Answer 52

**it is:** Umbilical Cord Histology **Contains:** Two umbilical arteries (A): blue arteries One umbilical vein (V): red vein Wharton’s jelly (W) primordial mucous connective tissue of the umbilical cord between amniotic epithelium and the umbilical vessels

Question 53

What are Syncytiotrophoblastic knots or syncytial knots?

Answer 53

Definition: Syncytiotrophoblastic knots or syncytial knots are aggregates of syncytial nuclei at the surface of terminal villi.

Question 54

What is the relation between syncytial knots and gestational age?

Answer 54

syncytial knots increase with increased gestational age.

Question 55

What is this

Answer 55