Embryogenesis and development 8 and 9

Question 1

What is cleavage?

Answer 1

Cell division in early embryo

Question 2

What is gastrulation?

Answer 2

Cell movements which produce gut and three primary germ layers

Question 3

What is organogenesis?

Answer 3

Development of organs

Question 4

Describe the features of sea urchin cleavage

Answer 4

Rapid divisions
Bastomeres all the same size
Holoblastic cleavage (division of whole cell)
Blastomeres become smaller with each division

Question 5

What is unequal holoblastic division?

Answer 5

Blastomeres in animal pole are
smaller than blastomeres in
vegetal pole because of presence
of yolk in vegetal hemisphere.

Question 6

When does unequal holoblastic division take place?

Answer 6

In amphibian cleavage

Question 7

What is mesoblastic cleavage?

Answer 7

Cleavage plane does not direct yolk

Question 8

What comes after the cleavage stage in chicks?

Answer 8

Blastula formation

Question 9

What do we refer to cells as in embryogenesis?

Answer 9

Blastomeres

Question 10

What is holoblastic division?

Answer 10

Cleavage plane divides the blastomere completely

Question 11

What is a morula?

Answer 11

After several cleavage divisions, the small sold ball of blastomeres that form

Question 12

Why are blastosomes the same size in sea urines?

Answer 12

There is no yolk in sea urine eggs

Question 13

Does the amphibian egg contain lots of yolk?

Answer 13

Yes

Question 14

What is the top pigmented half of the amphibian egg called?

Answer 14

Animal pole

Question 15

Whats is the unpigmented bottom half of the amphibian egg called?

Answer 15

Vegetal hemisphere

Question 16

What happens to the cytoplasm when the sperm enters the egg in amphibians?

Answer 16

Cytoplasm is rearranged and the cortex contracts towards the point of sperm entry revealing the grey crescent

Question 17

What is the dorsal surface marked with in amphibians?

Answer 17

Grey crescent

Question 18

What is the ventral surface marked with in amphibians?

Answer 18

Point of sperm entry

Question 19

Who undergo meroblastic cleavage?

Answer 19

Chicks

Question 20

What comes after blastula formation in chicks?

Answer 20

Gastrulation

Question 21

Gastrulations forms which 3 germ layers in chicks?

Answer 21

Ectoderm
Mesoderm
Endoderm

Question 22

What does the ectoderm include?

Answer 22

Epidermis of skin
Nervous system
Pituitary gland
Teeth

Question 23

What does the mesoderm include?

Answer 23

Muscular system
Skeletal system
Reporductive system
Dermis of skin

Question 24

What does the endoderm include?

Answer 24

Epithelial lining of gut, respiratory and excretory tracts

Question 25

Describe the process of gastrulation in sea urchins.

Answer 25

Cells at the vegetal pole thicken to form the vegetal plate which fold inwards forming the archenteron which form the endoderm Mesenchyme cells migrate into the blastocoel forming the mesoderm Cells remaining on the surface form the ectoderm

Question 26

Describe the process of gastrulation in chicks.

Answer 26

Straight invagination of the upper layer of cells of the blastoderm Cells migrate through blastocoel displace the hydroblast cells and form the endoderm Next cells migrate through the blastocoel to form the mesoderm Remaining cells on top form the ectoderm

Question 27

What is a primitive streak?

Answer 27

The line of invagionation in chick gastrulation

Question 28

Describe the process of gastrulation in amphibians.

Answer 28

Tuck at a site where grey crescent is situated which is called the dorsal lip of the blastopore The endoderm arises from cells lining the archenteron, the mesoderm arises from cells which were deep in the equator (marginal zone) and the ectoderm is derived from the cells remaining on the surface

Question 29

What do the amnion and chorion develop from in chicks?

Answer 29

Folds of ectoderm and mesoderm which extend over the top of the embryo and fuse

Question 30

What is the role of the amniotic sac in chicks?

Answer 30

Surround the embryo to protect it

Question 31

What is the amniotic sac lined with?

Answer 31

Amnion

Question 32

When is the first human cleavage?

Answer 32

24-30 hours after fertilisation

Question 33

What is formed fro the first human cleavage?

Answer 33

2 blastomeres

Question 34

When does the morula enter the uterus?

Answer 34

Day 4-5

Question 35

When does a blastocyst form during human fertilisation?

Answer 35

32 cell stage

Question 36

What does a blastocyst contain?

Answer 36

Inner cell mass Blastocoel Trophoblast

Question 37

What happens on the 5th day after human fertilisation?

Answer 37

Hatching: The blastocyst digests a hole in the zone pellucida and emerges

Question 38

What must occur before implantation in the uterus?

Answer 38

Hatching

Question 39

What happens during implantation?

Answer 39

Day 6-7 Blastocyst secretes enzymes to burrow unto endometrium Inner cell mass next to the endometrium

Question 40

What happens 8 days after human fertilisation?

Answer 40

Bilaminar embryonic disc is formed where the inner cell mass has rearranged into two layers called the epiblast (upper) and the hypoblast (lower)

Question 41

Describe the primitive streak in human gastrulation

Answer 41

Forms in dorsal epiblast | Defines anterior and posterior of the embryo

Question 42

How does gastrulation in humans form the 3 germ layers?

Answer 42

It enables the production of a trilaminar embryonic disc which consists of all 3

Question 43

What do cells form the primitive node produce?

Answer 43

notochord

Question 44

How does neurulation in vertebrates occur?

Answer 44

Notochord develops from dorsal mesoderm Induction of neural plate from ectoderm layer above the notochord A neural groove and neural folds form from the dorsal ectoderm The neural folds rise up, meet and fuse to form the neural tube

Question 45

What does the neural tube become?

Answer 45

CNS

Question 46

What are the first organs to develop in vertebrates?

Answer 46

Neural tube | Notochord

Question 47

What 3 components in development comprised of?

Answer 47

Growth Morphogenesis Differentiation

Question 48

WHAt happens in neurulation in amphibians?

Answer 48

Development of brain and spinal cord

Question 49

What is induction?

Answer 49

The fate of one cell is influenced by another

Question 50

What did the researchers do in the dorsal mesoderm experiment (1)?

Answer 50

Used two very early early newt embryos; unpigmented and pigmented. The dorsal lip of the blastopore from the unpigmented newt gastrula was transplanted into the ventral side of the pigmented newt gastrula

Question 51

What did the researchers find in the dorsal mesoderm experiment (1)?

Answer 51

Conjoined twins produced. Second embryo produced daily pigmented tissue.

Question 52

How did the organiser alter cell fate?

Answer 52

BMP-4 is uniformly distributed in late blastula and causes VENTRAL development. Chordin and Noggin (secreted by organiser) stop action of BMP-4 and allow dorsal development e.g. muscle and notochord (dorsal mesoderm)

Question 53

Describe the induction of the neural plate(2)

Answer 53

Signalling molecules from the notochord and surrounding cells cause the overlying ectoderm to take on a neural fate