Gastrulation- Birds

Question 1

Does fertilization occur internally or externally?

Answer 1

Internally after ovulation

Question 2

What is actually ovulated?

Answer 2

The yolk

Question 3

What kind of egg is a chick egg- with respect to the yolk?

Answer 3

-Teloecithal
-Lots of yolk

Question 4

Chick cleavage is-?

Answer 4

-Meroblastic/ incomplete
-Discoidal

Question 5

Is a one or two layered embryo produced?

Answer 5

-Two layered called a blastula
-Epiblast: all the embryo stuff is here
-Hypoblast: the thickened end where cells grow from and delaminate

Question 6

What is the blastocoel and where is it located?

Answer 6

-A fluid-filled space between the epiblast and the hypoblast

Question 7

What causes cells to move from an epiblast into an embryo?

Answer 7

-Ingression
-the migration of individual cells into the embryo
-this occurs along the midline grove- primative streak

Question 8

What occurs first in gastrulation?

Answer 8

-The epiblast thickens along the posterior marginal zone
-the cells here increase in height

Question 9

What occurs second in gastrulation?

Answer 9

-The thickened area elongates due to
-mediolateral cell intercalation
-cell migration to the posterior end of the embryo

Question 10

What occurs third in garstulation?

Answer 10

-The primitive streak is seen along the midline as it elongates to the thickened end
-Henson’s node appears near the anterior portion of the embryo

Question 11

What occurs last in gastrulation?

Answer 11

-Regression of the primitive streak
-the streak moves anteriorly
-Henson’s node moves posteriorly

Question 12

What is the head fold and what is its purpose?

Answer 12

-A fold located near the anterior portion of the embryo that involves all three layers
-It is used to lift up the head

Question 13

How does the body fold form?

Answer 13

-The outer germ layers are pinched in and the membranes will fuse
-the ectoderm and mesoderm will fuse to create the amniotic cavity
-the chorion forms here as well
-Allantois forms from the base of the hindgut to store waste
-allantois will grow and become vascularized until it touches chorion
-gas exchange will occur here then

Question 14

What is a differences in gastrulation in frog and chicks?

Answer 14

1. Chick embryos have a stronger anteroposterior gradient
   
   • the head-end has neuralation while the back-end does gastrulation
     -Henson’s node regresses

Question 15

What is the other main difference in gastrulation between frogs and chicks?

Answer 15

-Frogs have more yolk in the egg cells
-this helps with the energy they need to move on land