Embryology - Embryogenesis

Question 1

Name the 3 anatomical planes

Answer 1

• Frontal (coronal) : separates anterior & posterior
• Sagittal: Separates right and left sides
• Transverse (horizontal): separations superior and inferior

Question 2

How much time takes fertilization?

Answer 2

takes 24 hours

Question 3

What marks the beginning of fertilization?

Answer 3

Beggining of pre-embryonic period

Question 4

When does fertilization occurs?

Answer 4

When a spermatozoon and an oocyte contact and unite to form the zygote

Question 5

What initiate the cleavage of the zygote?

Answer 5

metabolic activation

Question 6

What could cause the death of a zygote

Answer 6

defect in the molecular and physical sequences

Question 7

What is the cleavage of the zygote exactly?

Answer 7

Consists of repeated mitotic division of the zygote

Question 8

What is the name of each cell after the mitotic division?

Answer 8

Blastomere

Question 9

Why do cells are tightly aligned against each other?

Answer 9

Allows better cell interaction

Question 10

whats the name of the 12-32 cell stage when it enters the uterus?

Answer 10

Morula stage

Question 11

What is surrounding the blastomere and the morula?

Answer 11

the Zona pellucida

Question 12

What happens to the size of the embryo during the blastomere and morula stage?

Answer 12

It does not increase in size

Question 13

Time line of blastomere, morula

Answer 13

2-cell stage = 30hrs
4-cell stage = 40hrs
8-cell stage = 60hrs
12-32-cell stage = 3-4 days (morula)

Question 14

what happens at day 5

Answer 14

The morula becomes hollowed by a fluid-filled space

Question 15

What is the name of the fluid filled space in the morula at day 5?

Answer 15

Blastocystic cavity

Question 16

What does the fluid to the blastocyst?

Answer 16

Separates the blastocyst into 2 parts

Question 17

What are the 2 parts of the divided blastocyst?

Answer 17

• outer cell layer : trophoblast (embryonic part of placenta)
• inner mass cell : embryoblast : gives rise to the embryo

Question 18

What forms the Blastocyst

Answer 18

Trophoblast, embryoblast and the blastocystic cavity

Question 19

what is the implantation and when does it happen?

Answer 19

Day 6-10 : blastocyst attaches to the endometrial epithelium

Question 20

In what does the trophoblast differentiates ?

Answer 20

2 layers:

• Cytotrophoblast : layer adjacent to embryoblast
• syncytiotrophoblast: invade endometrial epithelium to establish nutrient circulation

Question 21

From what is derived the nourishment for the nutrient circulation by the syncytotrophoblast ?

Answer 21

Nourishment is derived from the eroded maternal tissues

Question 22

What happens after the differentiation of the trophoblast, around day 8?

Answer 22

The blastocyst begins to be embedded in the endometrium

Question 23

What happens at day 9

Answer 23

Lacunae (small space) appears in the syncytiotrophoblast

Question 24

what happens around day 9-10?

Answer 24

The blastocyt sinks beneath the endometrial epithelium

Question 25

By what is filled the implantation site?

Answer 25

B y a closing plug - fibrin coagulum

Question 26

How are the lacunar networks formed and when?

Answer 26

around day 10-11, formed by fusion of adjacent lacunae

Question 27

When and how is the uteroplacental circulation established?

Answer 27

Syncytiotrophoblast erodes endometrial capillaries - around day 12

Question 28

Where usually occur the implantation?

Answer 28

In the uterine endometrium, the superior part of the uterus

Question 29

Where happens extrauterine pregnancies, usually?

Answer 29

uterine tube (95-98%)

Question 30

symptoms of ectopic/tubal pregnancy

Answer 30

abdo pain, tenderness, abnormal bleeding and peritonitis

Question 31

Where occur abdominal pregnancies?

Answer 31

on fimbriae, it could be expelled into the peritoneal cavity and will implant in the rectouterine pouch.

Question 32

is an abdo pregnancy viable?

Answer 32

May continue to full term and baby can be delivered by laparotomy

Question 33

Rewind to day 6-7, when the trophoblast proliferates and differentiates into 2 layers, something also happens to the embryoblast simultaneously, what happens?

Answer 33

The embryoblast undergoes morphological changes : bilaminar disc (2 layers) formation

Question 34

What are the 2 layers of the bilaminar disc of the embryoblast?

Answer 34

Epiblast and hypoblast

Question 35

What is the epiblast

Answer 35

Primary ectoderm: thick layer of columnar cell related to the amniotic cavity

Question 36

What is the hypoblast

Answer 36

Primary endoderm: cuboidal cell facing the blastocystic cavity

Question 37

How is the amniotic cavity created around day 7?

Answer 37

The amnioblast separates from epiblast to form the amnion enclosing the amniotic cavity

Question 38

How is the primary umbilical vesicle (yolk sac) created around day 7-8?

Answer 38

The hypoblast cell migrate and populate the inner surface of the blastocystic cavity forming the exocoelomic membrane with exocoelomic cavity. the hypoblast with exocelomic membrane form the yolk sac

Question 39

How is created the extraembryonic mesoderm around day 10-116

Answer 39

Hypoblast cells form a layer of connective tissue between the exocoelomic membrane and the cytotrophoblast

Question 40

How is called the space that appears in the extraembryonic mesoderm around day 12-13?

Answer 40

Extraembryonic ceolom (cavity)

Question 41

What does the extraembryonic coelom surrounds ?

Answer 41

It surrounds the amnion and the primary umbilical vesicle exept at the connecting stalk

Question 42

In what does the extraembryonic coelom separates the extraembryonic mesoderm into?

Answer 42

- extraembryonic somatic mesoderm : lining the trophoblast - Extraembryonic splanchnic mesoderm: lining yolk sac

Question 43

What is formed as the extraembryonic coelom forms ?

Answer 43

The secondary umbilical vesicle

Question 44

High yield diapo about implantation and embryoblast in brief (to review only, no question)

Answer 44

Question 45

When is the first stage of placenta

Answer 45

late second week

Question 46

What is a placenta

Answer 46

Fetomaternal organ for metabolic exchange between mother-embryo

Question 47

From what embryonic and trophoblastic structures is derived the palcenta?

Answer 47

Induced by extraembryonic mesoderm, cytotrophoblast column covered by syncytiotrophoblast, grow into the endometrium forming primary chorionic villi

Question 48

What is the chorionic villi

Answer 48

vascular process of the chorion

Question 49

Why do we want to maximize the surface area of where the placenta is implanted (the wave shaped chorionic villi)?

Answer 49

To maximize the contact with the maternal blood for nutrient and gaz exchange

Question 50

What is the chorionic sac

Answer 50

Composed of extraembryoninc somatic mesoderm and trophoblast layers.

Question 51

What is IN the chorionic sac

Answer 51

the embryo, amniotic sac and umbilical vesicle

Question 52

So, when is the fetomaternal circulation etablished?

Answer 52

When the primary chorionic villi appears, late 2nd week.