Development of trilaminar germ disc

Question 1

How many germ layers are in the trilaminar germ disc?

Answer 1

3

Question 2

What structure is the trilaminar germ disc derived from?

Answer 2

Bilaminar germ disc

Question 3

What is the first structure that forms in the development of the trilaminar germ disc?

Answer 3

Primitive streak

Question 4

What is the primitive streak?

Answer 4

Linear band of epiblasts in caudal end of bilaminar germ disc that consists of structures primitive node, groove, pit

Question 5

How does the bilaminar germ disc change shape, and what regions does it contain?

Answer 5

Elongates to become oval-shape, wider end is cranial region and narrower end is caudal region

Question 6

What direction does the primitive groove run in?

Answer 6

Caudally from midline

Question 7

How does the primitive node form?

Answer 7

Cranial end of primitive streak deepens

Question 8

What structure is within the primitive node, and what shape is it?

Answer 8

Primitive pit, which is a circular depression

Question 9

Which direction of primitive pit run in?

Answer 9

Runs continuously with primitive groove

Question 10

What body axis is determined by the primitive streak?

Answer 10

Cranial-caudal axis

Question 11

After the primitive streak is complete, what process occurs?

Answer 11

Ingression

Question 12

What is ingression?

Answer 12

Movement of epiblast cells through primitive streak and into interior of embryo

Question 13

When epiblasts migrate into primitive streak during ingression, what transition progress do they undergo?

Answer 13

Epithelium-to-Mesenchymal Transition (EMT)

Question 14

How is the structure of epithelial epiblasts different to the structure mesenchymal epiblasts?

Answer 14

Epithelial: tightly connected, regularly shaped, cuboidal

Mesenchymal: loosely connected, irregularly shaped, bottle-shaped

Question 15

What layer in the trilaminar germ disc do the first mesenchymal epiblasts form and how?

Answer 15

Mesenchymal epiblasts replace hypoblast to become endoderm

Question 16

After the endoderm has formed, what do the next ingressing mesenchymal epiblasts form in the trilaminar germ disc?

Answer 16

Migrate in between epiblasts and endoderm to form mesoderm

Question 17

After most epiblasts have ingressed, what do the remaining epiblasts form in the trilaminar germ disc?

Answer 17

Ectoderm

Question 18

What are the 4 types of mesoderm that are formed?

Answer 18

Paraxial, head, intermediate, lateral plate

Question 19

Where is paraxial mesoderm found?

Answer 19

Head and trunk region, lateral to notochord process

Question 20

How does head mesoderm form?

Answer 20

Paraxial mesoderm in the head region

Question 21

What does paraxial mesoderm form in the trunk region?

Answer 21

Somites

Question 22

What system does intermediate mesoderm form?

Answer 22

Urogenital

Question 23

What system does lateral plate mesoderm form?

Answer 23

Gastrointestinal, body wall