Gastrulation, Folding and Neurulation

Question 1

What is the depression at one end of the embryo?

Answer 1

Future mouth

Question 2

What is the primitive streak important for?

Answer 2

Driving gastrulation

Question 3

How many germ layers does gastrulation give rise to?

Answer 3

3

Question 4

Where is the primitive streak found?

Answer 4

Midline at the caudal end of epiblast

Question 5

What is found at the cranial end of the primitive streak?

Answer 5

Primitive pit and node

Question 6

Describe how 2 germ layers become 3

Answer 6

Cells lose attachments with others and migrate to primitive streak and dive down through it, this pushes epiblast and hypoblast apart

Question 7

What is the endoderm layer made up of?

Answer 7

Hypoblast cells and new cells from primitive streak

Question 8

What is the mesoderm layer made up of?

Answer 8

Migrating cells that push original cells apart

Question 9

What is the ectoderm layer made up of?

Answer 9

Original cells/left over cells

Question 10

What is the hypoblast replaced by?

Answer 10

Definitve endoderm

Question 11

What is the epiblast replaced by?

Answer 11

Ectoderm

Question 12

What layer forms between endoderm and epiblast?

Answer 12

Intraembryonic mesoderm

Question 13

What is the cloacal membrane?

Answer 13

Future anus

Question 14

What cells form the future notochord?

Answer 14

Cells that migrte through the node itself

Question 15

Describe the notochord process

Answer 15

Cells migrate throughthe primitive pit form a hollow mdline tube that extends cranially

Question 16

As the notochord moves down, what does it come into contact with?

Answer 16

Endoderm layer

Question 17

How does the notochord become a solid rod?

Answer 17

It loses connection with the endoderm and moves into the mesoderm layer

Question 18

Where can the notochord diffuse into?

Answer 18

Either side of the intermesoderm layer, ectoderm layer or endoderm layer

Question 19

After folding occurs, what happens to the ectoderm?

Answer 19

Gives up most of the outer layer of skin and nervous system (which starts at the epidermis of skin then sinks down into body)

Question 20

After folding occurs, what happens to the mesoderm?

Answer 20

Divides into 3 distinct groups: paraxial; intermediate; lateral (somatic and visceral)

Question 21

What is the paraxial mesoderm?

Answer 21

2 rods either side of the notochord on midline axis

Question 22

What is the lateral mesoderm?

Answer 22

Divides into somatic (associated with ectoderm) and visceral (associated with endoderm)

Question 23

What does the paraxial mesoderm contribute to?

Answer 23

Forms all vertebrae; some parts of brain; sternum; all voluntary muscle (bar head and neck); deeper layer of skin (dorsal midline dermis)

Question 24

What does the intermediate mesoderm contribute to?

Answer 24

Urogenital systems (ducts of gonads; gonads; kidney; ureter)

Question 25

What does the somatic mesoderm (lateral plate) contribute to?

Answer 25

Lining of body wall; most of dermis (bar back); skeletal elements of limbs

Question 26

What does the visceral mesoderm (lateral plate) contribute to?

Answer 26

Cardiovascular system (blood vessels and heart); mesotheial covering of organs; smooth muscle of organs

Question 27

What does the endoderm contribute to?

Answer 27

Lining of gut tube; lining of respiratory tract; lining of bladder and urethra (cloacal has divided into 2 parts)

Question 28

What are the 2 parts the cloaca divides into?

Answer 28

Posteriorly contributes to bladder and urethra; and anteriorly contributes to rectum and naus

Question 29

What surface is the neural plate found on?

Answer 29

Dorsal

Question 30

What happens to the primitive streak at the end of week 3?

Answer 30

It regresses

Question 31

What cells form neural plate?

Answer 31

Cells within ectoderm

Question 32

When ectoderm cells receive a signal from the notochord, what occurs?

Answer 32

They begin to differentiate towards a neural lineage

Question 33

How does the nervous system become protected?

Answer 33

The tissue needs to come into the body of the embryo; so the neural playe begins to fold in on itself; edges rise up and pull ectoderm witht it

Question 34

During day 20, what is more pronounced?

Answer 34

Neural groove/fold

Question 35

What occurs on day 22 of neural tube formation?

Answer 35

This is the first point of closure as edges of neural plate fuse and ectoderm fuses over the top

Question 36

What end closes first; cranial or caudal?

Answer 36

Cranial

Question 37

What day do the cranial/anterior neuropores close?

Answer 37

Day 24-25

Question 38

What day do the caudal/posterior neuropores close?

Answer 38

Day 26-28

Question 39

Where are neural crest cells found?

Answer 39

Between neural plate and ectoderm (they break and migrate)

Question 40

What ganglia has cells from neural crest?

Answer 40

Dorsal root; sympathetic; aortic gangli; ganglia of gut tube

Question 41

What releases hormones derived from neural crest cells?

Answer 41

Suprarenal gland

Question 42

What do neural crest migrations give rise to?

Answer 42

Non-neural structures (skin pigment cells)

Question 43

What are the neural crest derivatives?

Answer 43

Septum outflow of heart; bones of skull; eyes; cranial nerve ganglia; teeth; schwann cells