Gastrulation and Embryonic Germ Layers

Question 1

Zona Pellucida

Answer 1

Thick layer of glycoproteins that surrounds oocyte

Question 2

Purpose of Zona Pellucida

Answer 2

Helps with sperm recognition and binding

Question 3

Granulosa cells

Answer 3

Responsible for follicle development

Question 4

Cumulus oophorous

Answer 4

Anchor oocyte to follicle wall

Question 5

Mural granulosa cells

Answer 5

Line wall of follicle

Question 6

Corona radiata

Answer 6

Firmly anchor to zona pellucida; sperm must cross this layer to fertilize the oocyte

Question 7

What are the 3 types of granulosa cells?

Answer 7

Corona radiata, mural granulosa cells, cumulus oophorous

Question 8

List the 7 steps of fertilization

Answer 8

1. Acrosome reaction
2. Zona reaction
3. Fusion of egg and sperm cell membranes
4. Sperm head and tail enter ooctye cytoplasm
5. Formation of female and male pronuclei
6. Pronuclei fuse to form zygote
7. Chromosomes of zygote align on cleavage spindle

Question 9

What is the acrosome reaction?

Answer 9

Sperm head releases enzymes

Question 10

Why is the acrosome reaction important?

Answer 10

It allows the sperm to pass through the corona radiata and zona pellucida

Question 11

What is the zona reaction?

Answer 11

Changes in the zona pellucida

Question 12

Why is the zona reaction important?

Answer 12

It prevents the oocyte from being fertilized by more than one sperm by making the zona pellucida impermeable

Question 13

What happens after fertilization?

Answer 13

Cleavage

Question 14

What is cleavage?

Answer 14

Begins 30 hours after fertilization

Repeated mitotic divisions of zygote

Question 15

After 8 cells have been created, what happens?

Answer 15

Compaction

Question 16

What is compaction?

Answer 16

Cells squeezing in, taking smaller and more irregular shapes to fit inside

Question 17

Once 12-32 cells have been created what do you form?

Answer 17

Morula

Question 18

After the morula is formed, what happens next?

Answer 18

Blastogenesis

Question 19

What is blastogenesis?

Answer 19

Formation of a blastocyst and degradation of the zona pellucida

Question 20

What is does a blastocyst include?

Answer 20

Embryo and its membranes

• Trophoblast layer
• Embryoblast layer

Question 21

How long after initial penetration of the oocyte with the sperm does it take for blastocyst formation?

Answer 21

5-6 days

Question 22

Describe spontaneous abortions?

Answer 22

45%; occurs to zygotes, morulae, blastocysts;
Happens due to chromosomal abnormalities, inadequate hormone release
Usually before you know you are pregnant

Question 23

Where does the blastocyst attach?

Answer 23

Endometrial wall adjacent to its embryoblast layer

Question 24

What does the trophoblast layer differentiate into?

Answer 24

Cytotrophoblast and syncytiotrophoblast

Question 25

What does the cytotrophoblast do?

Answer 25

Release enzymes

Question 26

What does the syncytiotrophoblast do?

Answer 26

Use enzymatic degradation to invade endometrial wall to become superficially implanted

Question 27

What does the embryoblast layer differentiate into?

Answer 27

Epiblast and hypoblast

Question 28

What does the hypoblast do?

Answer 28

Continuous with exocoelomic membrane; lines cytotophoblast to create chorion

Question 29

What does the epiblast do?

Answer 29

Forms amniotic cavity and amnion

Question 30

Why is the epiblast important?

Answer 30

It protects the developing fetus

Question 31

What is the amnion?

Answer 31

Encloses embryo and houses amniotic fluid

Question 32

What is the bilaminar embryonic disc?

Answer 32

Epiblast + Hypoblast | *Day 6-10

Question 33

What is the primary umbilical vessel?

Answer 33

Hypoblast + lining of exocoelomic membrane

Question 34

What does the primary umbilical vessel give rise to?

Answer 34

Extraembryonic mesoderm

Question 35

What is the extraembryonic mesoderm?

Answer 35

Layer of tissue that surrounds amnion and umbilical vessel

Question 36

What happens to spaces in the extraembryonic mesoderm?

Answer 36

The spaces join and fuse to create the extraembryonic coelom

Question 37

What does the extraembryonic coelom do?

Answer 37

Forces the primary umbilical vessel to decrease in size

Question 38

What is the secondary umbilical vessel?

Answer 38

Forms from hypoblast cells, migrates inside of primary umbilical vesicle and it is the site of origin for primordial germ cells

Question 39

What does the extraembryonic coelom separate the extraembryonic mesoderm into?

Answer 39

Extraembryonic somatic mesoderm and the extraembryonic splanchic mesoderm

Question 40

Extraembryonic somatic mesoderm

Answer 40

Lines trophoblast and amnion

Question 41

Extraembryonic splanchic mesoderm

Answer 41

Surrounds umbilical vessel

Question 42

Chorion sac

Answer 42

Fetal component of placenta

Question 43

What is the chorion sac made of

Answer 43

Extraembryonic somatic mesoderm and trophoblast

Question 44

What is an ectopic pregnancy?

Answer 44

Implantation of the blastocyst outside the uterine cavity, usually in the oviduct

Question 45

Signs and symptoms of ectopic pregnancy

Answer 45

Profuse bleeding, abdominal pain, ruptured oviduct and occasional loss of ovary 2% of all pregnancies

Question 46

What is gastrulation?

Answer 46

Formation of trilaminar embryonic disc of primary germ layers

Question 47

When does gastrulation take place?

Answer 47

Week 3 of development

Question 48

What defines body axes; such as cranial-caudal, dorsal-vental, left-right?

Answer 48

Gastrulation

Question 49

First step in gastrulation?

Answer 49

Epiblast cells thicken to create the primitive streak and primitive node

Question 50

Cells in the middle of primitive streak and node die to become what?

Answer 50

Primitive groove and primitive pit

Question 51

What cells migrate into primitive groove?

Answer 51

Epiblast cells

Question 52

The hypoblast during gastrulation will become what?

Answer 52

Endoderm

Question 53

The epiblast layer during gastrulation will become what?

Answer 53

Ectoderm

Question 54

The cells that are migrating into the primitive groove and towards the cranial end become what?

Answer 54

Mesoderm

Question 55

What is the function of the notochord?

Answer 55

Primary signaling center in the embryo

Question 56

What is saccrococcygeal Teratoma?

Answer 56

Tumor made of pluripotent primitive streak cells | Mostly occurs in female and tumor grows at sacral end