Embryology

Question 1

What time duration does the process of embryology refer to ?

Answer 1

The time from conception to gastrulation

Question 2

What is a gamete

Answer 2

A germ cell with a haploid number of chromosomes - 23 single chromosomes in humans

Question 3

What is meiosis

Answer 3

The process of cell division which results in the formation of a haploid germ cells from diploid receptors

Question 4

What is a zygote

Answer 4

The earliest development stage formed by the combination of two gametes during fertilization

Question 5

Describe the week by week process

Answer 5

Early events - Gametogenesis
First week - Fertilisation, zygote formation and implantation
Blastocyst develops
Second week - Bilaminar germ disc
Third week - Gastrulation (including formation of the neural crest)
Fourth to eighth week - Embryonic period

Question 6

Describe the day by day process of early embryology

Answer 6

Day 1 - Fertilisation will occur
Day 2 - Cell division will occur until a small ball of cells known as a morula is produced
Day 3&4 - Morula begins to undergo some changes to form a blastocyst, with a blastocysts cavity and a thickened layer of cells at the other end

Question 7

What is a morula?

Answer 7

A small ball of cells that is produced by cell division

Question 8

How is a morula formed?

Answer 8

Morula is produced via the cell division of the zygote, and then produce a blastomere

Question 9

What happens to the morula after cell division

Answer 9

The morula will undergo compaction and cavitation

This then leads to the formation of a blastocyst

Question 10

What events are required for the formation of a blastocyst

Answer 10

Compaction and cavitation of the morula

Question 11

Describe compaction

Answer 11

• After several cleavage divisions, the individual blastomeres will adhere
• This involves CAM’s expression and gap junction formation
• This allows for cell-to-cell adhesion and intracellular communication

Question 12

Describe cavitation

Answer 12

• Formation of the ‘blastocyst cavity’ (Blastocele)

Question 13

What is a pluripotent cell

Answer 13

A cell that has the ability to develop into a variety of cell and tissue types in response to specific environmental stimuli

Question 14

What are the environmental stimuli needed to transform pluripotent cells into other cell types

Answer 14

• Cell-cell interactions
• Cell- matrix interactions
• Growth factors acting at an autocrine/ paracrine level

Question 15

Give examples of pluripotent stem cells

Answer 15

Embryonic stem cells
Hematopoietic stem cells
Bone marrow (stromal) stem cells

Question 16

What is the function of the trophoblast

Answer 16

Contacts with the endometrium of the uterus to facilitate implantation and the formation of the placenta