Embryology 2.1

Question 1

What is the endometrial layer called once implantation has occurred?

Answer 1

decidua

Question 2

What is the name given to the formulation of germ layers (layers that germinate) ?

Answer 2

gastrulation

Question 3

What is the name given to the formation of neural tube (tube that is going to form your brain and spinal cord) ?

Answer 3

neurulation

Question 4

What is one of the first things that happen in week 3?

Answer 4

primitive streak is formed in the midline of the epiblast by the dipping in of cells (invagination)

Question 5

What happens once the primitive streak is formed?

Answer 5

the axis of the embryo is formed- cells know which system it will go into

Question 6

Describe the process of the bilaminar disc becoming trilaminar disc (gastrulation)?

Answer 6

Cells in the primitive streak are rapidly reproducing through mitosis (cells all have the same genetic makeup)
New cells are going to sink down from the epiblast and form a new layer that sits between the epi and hypoblast.
New cells that are formed then go down and start to replace all of these cells in the hypoblast.
Bilaminar disc has now become trilaminar.

Question 7

What are the three germ layers of trilaminar disc?

Answer 7

ectoderm (top)
mesoderm (middle)
endoderm (bottom)

Question 8

What does it mean for each of these cells that they now belong to one of these three germ layers?

Answer 8

once these three germ layers are formed, each of the cells in each of these layers can only go on and form a certain set of structures

Question 9

What do cells of the ectoderm go on to form?

Answer 9

skin , your nervous system, your sympathetic trunk, dorsal root ganglia etc.

Question 10

What do mesodermal cells go on to form?

Answer 10

muscle tissue, skeletal tissue, urinary and reproductive system

Question 11

What does endoderm go on to form?

Answer 11

gut tube, respiratory tube etc..

Question 12

Describe what happens after the three germ layers have been formed and how the notochord forms after?

Answer 12

Cells of primitive streak continue to divide and start to sink down at the bottom and form a cluster of cells in the mesoderm.
The little rod of cells gets disconnected from the surface and forms something called as the notochord.

Question 13

Why is the notochord important in lower animals?

Answer 13

forms the backbone

Question 14

Where and why does the notochord secrete proteins?

Answer 14

proteins secreted go and act on the ectodermal layer and it thickens to form a little plate

Question 15

What is the name of the plate produced by the ectodermal layer thickening due to notochord protein secretions?

Answer 15

neural plate

Question 16

Describe the process of the neural plate becoming the neural tube?

Answer 16

the neural plate is going to dip down and form a valley shape.
Neural crests of the ectodermal layer come together until the two edges fuse with one another, forming a little tube.
Tube gets disconnected from the surface ectoderm and lies just underneath of it.

Question 17

What gene are the ectodermal cells that will go on to form the neural tube expressing?

Answer 17

SHH gene