L13 - Early Human Development

Question 1

What does embryogenesis achieve

Answer 1

Patterning - cells acquire identity in space and time
The major axes are defined
Three germ layers are defined
Rudiments of the major organs

Question 2

What are the major axes of the developing embryo

Answer 2

Anterior (head) and posterior (bottom)
Dorsal (back) and ventral (stomach)

Question 3

What are the 3 germ layers

Answer 3

Ectoderm, Mesoderm, Endoderm

Question 4

What is the path of the sperm cell

Answer 4

Corona radiata, Zona pellucida, plasma membrane of secondary oocyte, cytoplasm of secondary oocyte

Question 5

Why is egg much larger than sperm?

Answer 5

The egg contains nutrients and proteins required for early development

Question 6

What happens when male and female pronuclei fuse

Answer 6

Fertilisation, forms a zygote

Question 7

What is cleavage

Answer 7

A series of rapid cell division to form a blastocyst

Question 8

What is a morula

Answer 8

A ‘ball of cells’ formed through rapid cell division that occurs after fertilisation but before the blastocyst formation

Question 8

What does the embryoblast and trophoblast give rise to

Answer 8

Embryoblast - gives rise to embryo itself
Trophoblast - gives rise to extra embryonic tissue e.g placenta

Question 8

What does a blastocyst contain

Answer 8

Embryoblast (inner cell mass) and trophoblast

Question 9

Where does fertilisation occur

Answer 9

In the fallopian tube 12-24 hours after ovulation

Question 10

Where does implantation occur

Answer 10

In the uterus ~6 days after fertilisation

Question 11

What are the types of trophoblast cells

Answer 11

Syncytiotrophoblast and cytotrophoblast

Question 12

What is the enzyme we test for in a pregnancy test

Answer 12

Chorionic gonadotropin

Question 13

What is the chorionic villi

Answer 13

Projections of foetal placental tissue

Question 14

What is the bilaminar embryonic disc

Answer 14

Two layered structure formed by the the inner cell mass consisting of hypoblast and epiblast cells

Question 15

What germ layer do hypoblast and epiblast cells form

Answer 15

Hypoblast cells - endoderm
Epiblast cells - ectoderm

Question 16

What occurs during invagination in gastrulation

Answer 16

Formation of the mesoderm germ layer

Question 17

What is the step after gastrulation

Answer 17

Organogenesis

Question 18

What side of the embryo is the primitive streak on

Answer 18

Posterior side (bottom)

Question 19

What 2 parts form the future umbillical cord

Answer 19

Yolk sac and connecting stalk

Question 20

What is lateral folding in organogenesis

Answer 20

Ectoderm layer folds downwards to surround the embryo (forms skin)
Endoderm folds to form a tube (gut)

Question 21

What is the function of stem cells

Answer 21

Growth, renewal, repair

Question 22

What is an example of a tissue that is constantly renewing

Answer 22

Blood

Question 23

What is a stem cell

Answer 23

A cell that divides to form one daugther that goes on to differentiate and one daugther that retains its stem-cell properties

Question 24

What are the types of stem cells (from most to least potent)

Answer 24

Totipotent, pluripotent, multipotent, nullipotent (TPMN)

Question 25

What are totipotent cells

Answer 25

Cells capable of giving rise to all cell types of the body and extra-embryonic tissues (ZYGOTE)

Question 26

What are pluripotent cells

Answer 26

Cells capable of giving rise to all cell types of body (blastocyst)

Question 27

What are multipotent cells

Answer 27

Cells capable of giving rise to all cell types of a particular tissue or organ (e.g cells in gut)

Question 28

What are nullipotent cells

Answer 28

Cells not capable of giving rise to other cell types (e.g keratinocytes, RBCs)

Question 29

What are keratinocytes

Answer 29

Unipotent stem cells in the skin that allow for constant renewal

Question 30

What is epidermolysis bullosa (EB)

Answer 30

A mutation in a gene for collagen 7 that causes fragile, blistering skin

Question 31

What is a clinical utility of stem cells

Answer 31

Long lasting skin grafts (using CRISPR and gene editing) e.g for epidermolysis bullosa (EB)