Embryology

Question 1

What is embryology

Answer 1

Phase between fertilisation and birth

Question 2

Embryogenesis - from water to land
Problems + solutions

Answer 2

Problems
Dehydration, food availability
Solution
Formation of extra embryonic layers
- amniotic egg

Question 3

Extra embryonic layers

Answer 3

Amnion
Yolk
Allantois
Chorion

Question 4

Amnion

Answer 4

Prevents dehydration and protects embryo

Question 5

Yolk

Answer 5

Nutrition

Question 6

Allantois

Answer 6

Sequestering waste products

Question 7

Chorion

Answer 7

Exchanging respiratory gasses

Question 8

Characteristics of choradata

Answer 8

Notochord
Dorsal hollow nerve cord
Muscular anal tail
Pharyngeal slits or clefts

Question 9

What distinguishes vertebrates from other chordates

Answer 9

Development of back bone - vertebral column
Cranium
Endoskeleton

Question 10

What is the phylotipic stage

Answer 10

Tailbud stage

Question 11

1. Fertilisation

Answer 11

Fusion of the nucleus of a male gamete with the nucleus of a female gamete results in production of a zygote

Question 12

Sperm

Answer 12

Highly conserved features
Head has a cap called the acrosome which contains hydrolytic enzyme which help the sperm penetrates the egg

Question 13

Hydrolytic enzymes

Answer 13

Hyaluronidase - penetrates corona radiata
Acrosin - digests the sons pellucida

Question 14

Reproductive strategies

Answer 14

R selected - large no. Of small young, no parental care, rapid growth, short lived, high mortality risk

K selected - small no. Large young, parental care, long maturity, long lived

Effected by temp

Question 15

Telolecithal egg

Answer 15

Yolk down one end of the egg
- birds, reptiles, fish

Question 16

Isolecithal egg

Answer 16

Yolk is dispersed
- mammals -

Question 17

Amount of yolk

Answer 17

Small
Microlecithal - mammals
Mesolecithal - amphibians
Macrolecithal - fish, reptiles, birds
Large

Question 18

Egg laying

Answer 18

Oviparous

Question 19

Viviparous

Answer 19

Give birth to live young

Question 20

2. Cleavage

Answer 20

The series of mitotic divisions that take the zygote to a mass of smaller cells, blastula/blastocyst/blastoderm

Question 21

Two different forms of cleavage

Answer 21

Holoblastic - complete split of cells
- isolecithal
- microlecithal, mesolecithal

Meroblastic - partial cleavage
- telolecithal
- macrolecithal

Question 22

Cleavage in amphibians

Answer 22

Mesolecithal egg, radial holoblastic cleavage

Question 23

Cleavage in birds, fish and reptiles

Answer 23

Macrolecithal, discoidal meroblastic cleavage

Division occurs on top of yolk

Blastoderm
Bilaminar disc - 2 layers of cell formed;
1. Epiblast
2. Hypoblast

Question 24

Cleavage in mammals

Answer 24

Microlecithal egg, rotational holoblastic cleavage

Also asynchronous - not all blastomeres divide at the same time

Trophoblast - outer layer of cells = develops into placenta

Question 25

3. Gastrulation

Answer 25

Rearrangement of the cells by migration and division resulting in the formation of three embryonic germ layers :
1. Endoderm 2. Mesoderm 3. Ectoderm

Question 26

4. Neurulation

Answer 26

Folding process to form the neural tube which become the spinal chord and central nervous system

Question 27

Formation of yolk and allantois

Answer 27

Endoderm and mesoderm

Question 28

Formation of chorion and amnion

Answer 28

Ectoderm and mesoderm

Question 29

Placenta formation in mice

Answer 29

Formed for the Allantois and chorion

Question 30

5. Organogenesis

Answer 30

The series of organised integrated process that transforms an amorphous mass of cells into a complete organ in the developing embryo

Question 31

What does the ectoderm go on to form

Answer 31

• nervous system
• skin
• epithelia of eye, ear and nose

Question 32

Paradise mesoderm forms?

Answer 32

Connective tissue
- vertebrae, ribs
- muscle + limbs
- dermis (skin)

Question 33

Intermediate mesoderm forms?

Answer 33

Urogenital system
- kidneys, gonads

Question 34

Lateral plate mesoderm forms?

Answer 34

Circulatory system
- heart, vessels

Question 35

Archenteron

Answer 35

The primary gut formed during gastrulation

Question 36

Endoderm forms?

Answer 36

Intestines, lungs, liver, pancreas, thymus

Question 37

6. Differentiation

Answer 37

Embryonic cells specialise into diverse tissue structures

Question 38

Totipotent cells

Answer 38

each single blastomere contains the information to develop a complete individual

Question 39

What gene regulates organogenesis

Answer 39

Homeobox gene (hox gene)

Question 40

Homobox gene

Answer 40

Involved in differential gene expression and morphogenesis
Highly homologous
Master controllers

Question 41

Homeotic genes

Answer 41

Determine animal structure and they contain DNA sequences called homeoboxes