OCB02-1003 Embryogenesis

Question 1

How is the blastocyst formed

Answer 1

When the egg and sperm fuse, they form a zygote, which undergoes cleavage, and replicates to form a ball of cells

Question 2

How many cells are there in a blastocyst?

Answer 2

128

Question 3

What is the blastocyst comprised of?

Answer 3

An inner cell mass which contains the embryonic stem cells
An outer layer of cells called the trophectoderm
The blastocele which is a fluid filled cavity

Question 4

What process occurs 6 days after fertilisation?

Answer 4

Implantation

Question 5

What occurs during implantation?

Answer 5

The trophoblast cells begin to infiltrate the wall of the uterus

Question 6

What process takes place after cleavage an formation of the blastocyst?

Answer 6

Gastrulation

Question 7

Overall what does gastrulation do?

Answer 7

It reorganises the bilaminar disc int the 3 germ layers?

Question 8

What is the bilaminar disc made up of?

Answer 8

Epiblast layer

Hypoblast layer

Question 9

What are the names of the 3 germ layers?

Answer 9

Ectoderm
Mesoderm
Endoderm

Question 10

How does the bilaminar disc form?

Answer 10

The inner cell mass divides into the epiblast and hypoblast

Question 11

What forms as the epiblast and hypoblast grows and is the site of gastrulation?

Answer 11

Primitive streak

Question 12

What occurs during gastrulation?

Answer 12

Cells in the epiblast move towards the primitive streak
Cells leave the epiblast and ingress into the primitive streak
Ingressing cells form the endoderm as they are pushed into the hypoblast layer
Cells that come out of the epiblast later form the mesoderm
Cells that remain at the surface form the ectoderm

Question 13

What are the derivatives of the ectoderm?

Answer 13

Skin

Nervous system

Question 14

What are the derivatives of the mesoderm?

Answer 14

Vertebral column
Skelton
Skeletal muscle
Blood

Question 15

What are the derivatives of the endoderm?

Answer 15

GIT

Question 16

What do the position of cells along the primitive streak determine?

Answer 16

Their final position in the dorso-ventral axis

Question 17

Where do cells from the anterior tip of the streak go to?

Answer 17

notochord

Question 18

Where do cells from the posterior tip of the streak move to?

Answer 18

Paraxial somites of mesoderm

Question 19

What initiates the neuralation process?

Answer 19

notochord

Question 20

What is neuralation?

Answer 20

The folding process by which the neural plate forms the neural tube

Question 21

What occurs in the process of neuralation?

Answer 21

The neural plate forms in the ectoderm and it broadens and its ends begin to fold upwards
As the fold gains height, a neural groove forms
The fold will eventually close to form the neural tube

Question 22

What happens to the endoderm during neuralation?

Answer 22

The endoderm moves towards the midline of the body and fuses to create the primitive gut tube

Question 23

What are the 3 sections of the primitive gut?

Answer 23

foregut
midgut
hindgut

Question 24

What are neural crest cells and what will they form?

Answer 24

They are migratory cells that bud off when the neural tube was formed
They will form PNS and autonomic ganglion etc

Question 25

What will neural tube form?

Answer 25

The brain and spinal cord

Question 26

What is another name for the head and tail axis?

Answer 26

Rostral- caudal