CTCS Quiz 4: Embryos

Question 1

Amnion

Answer 1

a fluid-filled sac encasing embryo that protects it from shock.

Question 2

Blastocyst/Blastula

Answer 2

early embryo composed of two tissues: trophectoderm and inner cell mass

Question 3

Blastomere

Answer 3

cells resulting from cleavage of zygote

Question 4

Cleavage

Answer 4

cell division and mitosis without intervening periods of cell growth.

Question 5

Differenctiation

Answer 5

the process by which cells become molecularly and morphologically distinct from one another

Question 6

Epiblast

Answer 6

cell layer derived from inner cell mass that gives rise to embryo proper and amnion epithelium

Question 7

Hypoblast

Answer 7

cell layer derived from ICM, a transient embryonic tissue that gives rise to the yom sac and has important signaling functions.

Question 8

Morula

Answer 8

many blastomeres

Question 9

Regulation

Answer 9

property of early embryo, it can develop normally when cells are removed or added

Question 10

Zona pellucida

Answer 10

acellular, glycoprotein layer that surrounds the oocyte, plays a role in fertilization, keeps blastomeres together prior to compaction, plays a role in the temporal regulation of implantation

Question 11

Zygote

Answer 11

fertilized oocyte

Question 12

Totipotent

Answer 12

cells that can become any type of tissue, including placenta.

Question 13

Pluripotent

Answer 13

these cells can give rise to all body tissues, but they cannot be placenta.

Question 14

What does the Paraxial Mesoderm make? What does that make? What does that make?

Answer 14

Paraxial > Somite (also head) > sclerotome (cartilage), myotome (skeletal muscle) and dermatome (dermis)

Question 15

How many pairs of somites are there in total?

Answer 15

38 pairs.

Question 16

How many pairs of occipital somites? Cervical somites? Thoracic? Lumbar? Sacral? Coccygeal?

Answer 16

Occipital:  4
Cervical:  8
Thoracic:  12
Lumbar:  5
Sacral:  5
Coccygeal:  3

Question 17

What does retinoic acid do in the formation of somites?

Answer 17

promotes differentiation of paraxial mesoderm into somite tissue.

Question 18

What does Fibroblast Growth Factor (FGF) do in terms of somite formation?

Answer 18

It opposes somite differentiation.

Question 19

What would happen without the cycling genes in terms of somite formation?

Answer 19

You would end up with one, big french baguette of a somite.

Question 20

What conditions must be met for a somite to form?

Answer 20

RA opposes FGF in an area that co-localizes with cycling genes.

Question 21

What does the dermatome split into? What do they split into?

Answer 21

Dermatome > epimere and hypomere
Epimere: deep epaxial muscles of back
Hypomere: hypaxial muscles or lateral and ventral body.

Question 22

When do somites gain their regional specificity?

Answer 22

From their precursor. If you transplant a thoracic somite to the lumbar, it will still grow ribs.

Question 23

What tissue layer forms lacunae?

Answer 23

Exra-Embryonic Mesoderm

Question 24

What is formed when all the lacunea merge?

Answer 24

Chorionic cavity. (or extra-embryonic coelom or getional sac)

Question 25

What does the yolk sac do?

Answer 25

First place to generate blood cells, forms niche for germ line and provides extra space for gut elongation.

Question 26

What forms the dorsal/ventral axis?

Answer 26

The endoderm (ventral) and ectoderm (dorsal)

Question 27

What are the two things that neural fate is dependent on?

Answer 27

1. Robust FGF signalling in the responder
2. inhibition of Bmp signalin in the inducer
   * without these two things the cells turn into epidermis instead of spinal cord.