T4-Weeks 3 and 4 of development

Question 1

Week in which gastrulation occurs

Answer 1

Week 3

Question 2

Where does the primative streak form?

Answer 2

at the caudal end of the epiblast

Question 3

Features of primative streak

Answer 3

Clearly visible by day 15/16 Sets up each axis of the body

Question 4

Cranial tip of the primative streak

Answer 4

primative node

Question 5

Primative node

Answer 5

slightly elevated area surrounding a small primative pit

Question 6

Primative streak is active until when?

Answer 6

the early part of the 4th week

Question 7

Primitive streak results from what?

Answer 7

growth and movement of epiblast cells to the middle of the embryonic disc

Question 8

The process of invagination

Answer 8

Epiblast cells migrate towards the primative streak, become flask shaped, detach from epiblast, and slip inwards

Question 9

Invaginating cells that displaces hypoblast cells forms what?

Answer 9

endoderm

Question 10

Invaginating cells that end up between endoderm and epiderm

Answer 10

mesoderm

Question 11

Non-migrating epiblast cells form what structure?

Answer 11

ectoderm

Question 12

General functions of the notochord

Answer 12

-induces neurulation, -provides signals for future musculoskeletal development -indicates future site of vertebral bodies -assists in defining embryo axis

Question 13

What is the prechordal plate

Answer 13

a small circular area of columnar endodermal cells at the cranial end of the embryo where ectoderm and endoderm are fused

Question 14

What day does the allantois begin to form

Answer 14

about day 16

Question 15

What does neurulation represent

Answer 15

the beginning of nervous system development

Question 16

When does neurulation begin and end

Answer 16

Starts at day 18; ends by the end of week 4

Question 17

What does allantois begin as

Answer 17

a small diverticulum from the caudal wall of the umbillical vessicle, extending into the connecting stalk

Question 18

What will the allantois do

Answer 18

serve a role in the development of umbillical blood vessels as well as urogenital structures

Question 19

Notochord induces __________ to thicken into___________

Answer 19

overlying ectoderm; neural plate

Question 20

At day______, edges of the neural plate (__________)elevate and bend towards each other___________

Answer 20

18; neural folds; dorsally

Question 21

Neural tube eventually becomes what?

Answer 21

brain and spinal cord

Question 22

Day that cranial neuropore closes

Answer 22

day 25

Question 23

Day that caudal neuropore closes

Answer 23

day 27

Question 24

Which day is this

Answer 24

Day 16

Question 25

What day is this?

Answer 25

Day 16

Question 26

Which day is this

Answer 26

Early day 18

Question 27

Which day is this

Answer 27

Middle of day 18