Lecture 2

Question 1

Describe the basic steps that are involved in gastrulation:

Answer 1

Gastrulation: Hollow blastula invaginates to for a three-layered embryo with a primitive gut. Blastopore forms anus in deuterostomes and the mesoderm cavitates to form a primary coelom • Endoderm is replaced by gastrulating cells that invade and replace the entire hypoblast layer • Ectoderm formed by cells remaining in the epiblast • Mesoderm formed by cells that migrate between these two layers • Protostomes- mouth first, deuterostomes- mouth second

Question 2

Describe the basic steps that are involved in the process of neurolation:

Answer 2

1. Notochord forms within the mesoderm layer 2. Signals the development of the neural plate in the surface ectoderm that lies above it 3. A neural groove forms with neural crest cells on either side 4. The neural groove will then migrate downwards forming the cells on either side of it 5. The neural crest cells will then eventually migrate to form other seperate parts of the body

Question 3

State the three basic germ layers and state what these will eventually differentiate into:

Answer 3

• Ectoderm- the outermost layer- epidermis and nervous tissue • Mesoderm- the middle layer – muscle and connective tissues • Endoderm- inner layer- gut, liver, lungs

Question 4

Where is the chorion located and what is its function?

Answer 4

Outermost layer- gas exchange surface

Question 5

Where is the amnion located and what is its primary function?

Answer 5

Surrounds the embryo- provides a cushion and provides . a favourable ionic and osmotic gradient

Question 6

Where is the allantois located and what is its primary function?

Answer 6

Allantois- highly vascularised delivering gases between the embryo and the outer surface layer + stores nitrogenous waste in birds and reptiles

Question 7

Name the following types of placentas and give an example of a species for each:

Answer 7

1. Diffuse- horses, pigs, camels
2. Cotyldonary- bovines
3. Zonary- carnivors
4. Discoid- primates and rodents

Question 8

Define the term gastrula/gastrulation:

Answer 8

The formation of the germ layers an important part of embryonic period of development. At the formation of the germ layers the blastula is transformed into a gastrula.

Question 9

Define the term primative streak:

Answer 9

Refers to a streak of villi where the gastroblasts migrate inwards

Question 10

Define the term trilaminar/triploblastic disc:

Answer 10

Early stage of development involved within triploblastic organisms

Question 11

Define the term germ layers:

Answer 11

Refers to the three primary layers that are involved in development

Question 12

Define the term germ cell:

Answer 12

simply refers to a haploid cell, the has the ability to combine with another cell to form a fully diploid nucleus

Question 13

Define the term coelum:

Answer 13

simply a body cavity that occurs within animals

Question 14

Define the term neural groove:

Answer 14

a shallow medium groove of neural plate between the neural folds of an embryo. Neural plate is a thick sheet of ectoderm surrounded on either side by the neural folds.

Question 15

Define the term Amnion:

Answer 15

surrounds the embryo filled with fluid acting as a cushion and providing a favourable ionic and osmotic environment

Question 16

Define the term chorion:

Answer 16

outermost layer gas exchange surface

Question 17

Define the term allantois:

Answer 17

highly vascularised delivers gases between the embryo and the outer surface layers- stores nitrogenous wastes in birds and reptiles