Embryology

Question 1

What occurs within the first week of embryology

Answer 1

Ovulation
Fertilisation
Implantation

Question 2

Roughly when does implantation occur

Answer 2

5 1/2 - 6 days

Question 3

What is a zygote

Answer 3

A fertilised ovum

Question 4

What is a morula

Answer 4

A mass of cells resulting from division or a fertilised ovum

Question 5

What is a blastocyst

Answer 5

A hollow ball of cells:
-Inner cell mass
-Trophoblast

Question 6

What is the purpose of the placenta

Answer 6

A way to transfer nutrients and waste to and from the mother

Question 7

When might a baby and mother’s circulatory system interact

Answer 7

During birth

Question 8

Is the placental barrier permeable

Answer 8

Yes to most molecules but not cells

Question 9

What is an embryological difference between identical and fraternal twins after implantation

Answer 9

Fraternal twins each have a placenta while identical twins share a placenta

Question 10

When does the implanted trophoblast contain a bilaminar embryo

Answer 10

10-12 days

Question 11

What layers does the bilaminar embryo have

Answer 11

Epiblast layer
Hypoblast layer

Question 12

What does the epiblast layer give rise to

Answer 12

Embryonic ectoderm
Mesoderm
Endoderm
Mesendoderm?

Question 13

What does the hypoblast layer participate in

Answer 13

Formation of endoderm and extraembryonic mesoderm

Question 14

What does the embryo develop during gastrulation

Answer 14

An axis (becomes bilaterally symmetrical)
The three embrionic cell layers

Question 15

What is the key stage of gastrulation

Answer 15

Formation of a groove, the primitive streak

Question 16

What does organogenesis mean

Answer 16

Generating an organ

Question 17

What forms the mesoderm

Answer 17

Ectodermal cells induced to differentiate and migrate through the primitive streak towards the hypoblast

Question 18

What forms the third layer to form the trilaminar embryo

Answer 18

The mesodermal cells push through the primitive streak and spread out to form a third layer

Question 19

What is one of the first organs to be formed

Answer 19

Central nervous system

Question 20

What is developing muscle called

Answer 20

Somite

Question 21

When is the neural groove evident

Answer 21

19,20 days when the embryo is about 2mm long

Question 22

What is the order of development of the central nervous system

Answer 22

Neural fold
Neural groove
Neural tube
Dorsal root ganglion

Question 23

What defects are associated with the neural groove

Answer 23

Spina bifida -non closer of neural groove lack of formation of the neural tube

Question 24

When do the cells become a foetus

Answer 24

Week 9 as there is development of organs

Question 25

Why is the neural crest also known as 'ectomesenchyme'

Answer 25

Derived from ectoderm but has the characteristics of mesenchyme

Question 26

Approx how long is the embryo at 7 weeks

Answer 26

27mm

Question 27

What length is the fetus at weeks 9,14,20

Answer 27

44mm 120mm 185mm

Question 28

Where do all body cells originate from

Answer 28

3 cell types: -Ectoderm: outer covering -Mesoderm: middle -Endoderm: inner lining

Question 29

When does the face start to form

Answer 29

Week 4-7 via migration of cells from posterior to anterior region

Question 30

Which stem cells are totipotent

Answer 30

Embryonic inner cell mass - capable of giving rise to any cell type

Question 31

Which embryonic stem cells are pluripotent

Answer 31

Cells in the 3 germ layers

Question 32

What does stem cell development involve

Answer 32

Genes and various signalling molecules

Question 33

What does the ectoderm compose

Answer 33

Skin TOOTH ENAMEL Mucous membranes of mouth,anus Brain, spinal chord

Question 34

What structures are made of mesoderm

Answer 34

Most connective tissues -Dermis, tendons, cartilage, bone Muscle (most) Blood vessels Kidney and urinary system Reproductive system Serous membranes

Question 35

What does the endoderm make up

Answer 35

Alimentary canal (pharynx - rectum) Respiratory system Parts of urogenitakl system

Question 36

What is the 'fourth' primary embryonic layer

Answer 36

Ectomesenchyme

Question 37

What does the ectomesenchyme give rise to

Answer 37

Most of the peripheral nervous system: sensory + autonomic Melanocytes Adrenal medulla Most of the mesenchyme in the head Dentine, cementum, pulp, periodontal ligament, jaw bones

Question 38

When is the period of greatest sensitivity for development in utero

Answer 38

First trimester: weeks 3-12

Question 39

When do teeth begin to form in utero

Answer 39

week 6-7

Question 40

When are primary teeth fully formed

Answer 40

Around week 9