Early Embryonic Development

Question 0

What is a 2 cell morula?

Answer 0

It is an embryo at an early stage. A spherical mass of blastomeres, the first cells of fertilization.

Question 1

The morula goes through a 2 cell, and a 4 cell stage and continues to divide. At around 80 hours it is called:

Answer 1

An early morula. This is a multi-cell stage.

Question 2

What does the morula do once it reaches the uterus? What is it called now? And how much time has passed?

Answer 2

1) It begins to take up fluid from it’s surroundings
2) It is now called a blastocyst
3) Around 5 days have passed since fertilization

Question 3

The wall of the blastocyst consists of:

Answer 3

A single layer of flattened cells (the trophoblast), and an inner cell mass called the embryoblast.

Question 4

What are the trophoblast cells responsible for?

Answer 4

The attachment of the blastocyst to the uterine epithelium and the implantation into the endometrium.

Question 5

With implantation, what do the cells of the trophoblast layer do?

Answer 5

They differentiate into a cyto and syncytiotrophoblast and will eventually form the outer embryonic membrane (the chorion) and the fetal portion of the placenta.

Question 7

The embryo develops from ________ which also contributes to the formation of __________ .

Answer 7

The inner cell mass, called the embryoblast.

The amnion and the yolk sac.

Question 7

What happens after the two layers form the embryonic disc?

Answer 7

A space appears between the inner cell mass and the trophoblast layer to form the amniotic cavity.

Question 8

The inner cell mass then divides into ______ ? And these layers form _______ ?

Answer 8

2 layers. The inner layer is called the entoderm, while the outer layer is called the ectoderm.
The embryonic disc.

Question 9

The amniotic cavity is lined by:

Answer 9

Ectodermal cells of the embryonic disk and amniogenic cells derived from the trophoblast.

Question 10

The entodermal cells are then separated from the trophoblast by:

Answer 10

The extra embryonic mesoderm.

Question 11

The cavity of the blastocyst becomes lined on the inside by _______ migrating from __________ to form _____________ .

Answer 11

Entodermal cells
The inner cell mass
The primitive yolk sac.

Question 13

The embryo proper is now a ________ .

Which will form _______ .

Answer 13

Disc made up of 2 layers of cells

All the intraembryonic tissues

Question 14

Ectodermal cells migrate between the _____ and the _____ which now gives rise to __________.

Answer 14

Ectoderm and entoderm

The intraembryonic mesoderm, the 3rd layer.

Question 14

What are the 3 germ layers?

Answer 14

The entoderm, the inside layer. The mesoderm, the middle layer, and the ectoderm, the outer layer.

Question 15

The entoderm later will help form 1)____, 2)____, and 3)____.

Answer 15

1) Respiratory system 2) Digestive system 3) Bladder

Question 16

The ______ and ______ are separated by the ______ except at the __________ where the entoderm has thickened. The embryo is now ___ days old.

Answer 16

Ectoderm and entoderm; Mesoderm; Prochordal plate;

20 days old.

Question 17

The mesoderm later will help form 1) ___, 2) ___, 3) ___, 4) ___, 5) ___, 6) ___, 7) ___.

Answer 17

1) Connective tissue 2) Bone 3) Muscle, including heart & pericardium 4) Vascular system 5) Lymphatic system 6) Kidneys 7) Cartilage

Question 18

The ectoderm later will help form 1) ___, 2) ___, 3) ___, 4) ___, 5) ___, 6) ___.

Answer 18

1) Skin 2) Hair 3) Nervous system 4) Brain 5) Spine 6) Nails

Question 20

Mesodermal cells continue to migrate until _____ and _____ are separated from each other by _____ _____, except at the prochordal plate.

Answer 20

Ectoderm and entoderm cells

Intraembryonic mesoderm

Question 21

The intraembryonic mesoderm has separated the entoderm and ectoderm from each other everywhere except at the _____, which remains bilaminar. This bilaminar part later becomes the _______ _____.

Answer 21

Prochordal plate

Buccopharyngeal membrane

Question 22

The formation of the celom separates the Mesoderm into two layers: _______ and the _______ .

Answer 22

Splanchnopleuric Mesoderm

Somatopleuric Mesoderm

Question 23

The Splanchnopleuric Mesoderm is in contact with the ________ .

Answer 23

Endoderm / Entoderm

Question 24

The Somatopleuric Mesoderm is in contact with the ________ .

Answer 24

Ectoderm