Gastrulation

Question 1

What is gastrulation?

Answer 1

Process by which blastula is transformed into an embryo , with tissue layers and body axis.

Question 2

What is the embryo called during gastrulation?

Answer 2

Gastrula

Question 3

What are the three layers that may form (only two in diploblastic)?

Answer 3

Mesoderm, endoderm, ectoderm

Question 4

What is the endoderm?

Answer 4

Inner layer, forming digestive tract, circulatory tract and respiratory tract

Question 5

What is the ectoderm?

Answer 5

outer layer, forming epidermis and nervous system

Question 6

What is the mesoderm?

Answer 6

Middle layer, forming bone, muscle, liver, heart, blood vessels

Question 7

What is the result of gastrulation?

Answer 7

Some of the cells at or near the surface of the blastula move to an interior location and three cell layers are established, allowing cells to interact in new ways and leads to generation of body organs

Question 8

Where does gastrulation beginning sea urchins, birds and frogs, and what happens?

Answer 8

At the vegetal pole, where individual cells detach from the blastocoel wall and enter the blastocoel as migratory cells.

Question 9

What are mesenchyme cells?

Answer 9

Loosely organised migratory mesodermal tissue that develops into connective and skeletal tissue

Question 10

How does the vegetal plate form?

Answer 10

Cells remaining at the vegetal pole after gastrulation flatten slightly

Question 11

What is invagination?

Answer 11

Vegetal plate buckles inwards as a result of cell shape changes, cells are then extensively rearranged and invagination deepens, forming a narrow blind ended tube

Question 12

What is the archenteron?

Answer 12

Blind ended tube formed in invagination, open end is called the blastopore

Question 13

What does the blastopore become in proteostomes?

Answer 13

The mouth

Question 14

How does the mouth form in deuterostomes?

Answer 14

A second opening forms when the opposite end of the archenteron reaches the inside of the ectoderm and the two laters fuse, producing a rudimentary digestive tube

Question 15

Why are mechanisms of gastrulation more complex in frogs?

Answer 15

Because of the large yolky cells in the vegetal hemisphere

Question 16

Where does gastrulation begin in frogs?

Answer 16

On the dorsal side of the blastula when a group of cells begins to invaginate

Question 17

What is the dorsal lip?

Answer 17

Part above the crease in frog gastrulation which becomes the dorsal side of the blastopore

Question 18

What is involution?

Answer 18

Layers at the surface of the embryo roll over the edge of the lip into the interior of the embryo - becomes mesoderm and endoderm

Question 19

What happens to the blastocoel during gastrulation in frogs?

Answer 19

Collapses as it is displaced by the archenteron that is formed

Question 20

What happens to the circular lip of the blastopore once gastrulation is completed?

Answer 20

Surrounds a yolk plug consisting the outer nutrient laden cells

Question 21

Why is gastrulation different in chicks?

Answer 21

The inward movement of cells is affected by the large mass of yolk pressing against the bottom of the embryo

Question 22

What is the epiblast?

Answer 22

Upper layer of gives rise to the three primary germ layers and extra embryonic layers

Question 23

What is the blastoderm stage?

Answer 23

Consists of upper and lower layers, epic and hypoblast, lying atop the yolk mass.

Question 24

What happens during gastrulation in chicks?

Answer 24

Some epiblast cells move inward at the blastoderm and then detach and move inward toward the yolk. Forms the primitive streak

Question 25

What is the primitive streak?

Answer 25

Functionally equivalent to blastopore in frogs, but oriented differently. An opening by which the cavity of the gastrula communicates with the exterior.

Question 26

What is the function of the hypoblast?

Answer 26

Seems to direct the formation of the primitive streak before the onset of gastrulation

Question 27

When is gastrulation complete?

Answer 27

When all germ layers have formed

Question 28

What is a blastocyst?

Answer 28

In mammalian developement, possesses an inner cell mass that eventually becomes the embryo. Outer layer is called the trophoblast and forms the placenta