Embryology

Question 1

Zygote

Answer 1

One cell but 2n (made up of female pronucleus and male pronucleus)

Question 2

When does the morula form and what is it made of

Answer 2

Day 3/4

Morula is made up of blastomeres (about 16)

Question 3

When does blastocyst form

Answer 3

Day 5

Question 4

When does formation of primitive germ layers take place

Answer 4

3rd week

Question 5

When does organogenesis take place

Answer 5

Embryonic period
2-8 weeks

Question 6

When is the fetal period

Answer 6

9-38 weeks
Growth differentiation and maturation

Question 7

Totipotent pluripotent multipotent unipotent

Question 8

What makes up the blastocyst

Answer 8

Embryoblast (inner cell mass) and trophoblast (outer)

Question 9

What needs to be present in uterus lining for successful implantation of blastocyst

Answer 9

Progesterone

Question 10

What lines the inner wall of the blastocyst after implantation

Answer 10

Inner cystotrophoblast
Outer synctiotrophoblast

Question 11

What forms the bilaminar disc

Answer 11

Hypoblast
Epiblast

Question 12

What is the histology and location of the hypoblast and epiblast

Answer 12

Hypoblast cuboidal and ventral
Epiblast columnar and dorsal

Question 13

What is the function of the placenta

Answer 13

Life support,
Provides oxygen and nutrients removes waste
Circulations of baby and mother blood do not mix, separated by thin barrier

Question 14

Chorionic villus sampling

Answer 14

Chorionic villus sampling may be used for genetic and chromosome testing in the first trimester of pregnancy . Here are some reasons that a woman might elect to undergo CVS:

Previously affected child or a family history of a genetic disease, chromosomal abnormalities, or metabolic disorder

Maternal age over 35 years by the pregnancy due date

Risk of a sex-linked genetic disease

Previous ultrasound with questionable or abnormal findings

Abnormal cell-free DNA test

Question 15

Difference between identical and fraternal twins at the trophoblast stage

Answer 15

Identical twins are from the same trophoblast fraternal twins are from two different trophoblasts

Question 16

How does the trilaminar embryonic disc form

Answer 16

Ectoderm - leftover Epiblast
Mesoderm - Epiblast cells that migrated inwards
Endoderm - Epiblast cells that replaced Hypoblast layer

Question 17

When does gastrulation take place

Answer 17

Day 15 , start of week 3

Question 18

First organ to be developed

Answer 18

CNS

Question 19

What are the derivates of the ectoderm germ layer

Answer 19

Skin
ENAMEL
Mucous membranes
CNS

Question 20

Derivatives of the mesoderm

Answer 20

Most connective tissues (dermis, tendons, cartilage, bone)
Muscle
Blood vessels
Heart
Kidney
Reproductive system

Question 21

Derivatives of the endoderm

Answer 21

Thyroid
Parathyroid
Respiratory
GIT
Irogenital (some)

Question 22

When does spontaneous abortion occur

Answer 22

First. 2 weeks

Question 23

First trimester period

Answer 23

Week 3-12
Greatest sensitivity

Question 24

Ectomesenchyme importance in dentistry

Answer 24

Derivatives are dentine cementum pulp PDL jaw bones
Most of the mesenchyme in the head
PNS

Question 25

What is ectomesenchyme

Answer 25

Another name for neural crest Very important for development of head Derived from ectoderm but has characteristics of mesenchyme

Question 26

Where does primitive streak extend from

Answer 26

Formation of primitive node , primitive node and primitive pit extends towards the caudal end forming the primitive groove (cranial end of primitive streak expands)

Question 27

What does dental papilla cells differentiate into? What does IEE cells differentiate into?

Answer 27

Dental papillae cells into odontoblasts IEE cells differentiate into ameloblasts

Question 28

Stomodaeum

Answer 28

Primitive mouth

Question 29

What forms the enamel organ and what forms the dental papilla

Answer 29

Ectoderm cells into dental lamina into enamel organ Ectomesenchyme condensation into dental papilla

Question 30

What is the name of the point where EEE and IEE meet

Answer 30

Cervical loop (Extends apically in root formation)

Question 31

4 cells of enamel organ

Answer 31

Stratum intermedium IEE EEE Stellatereticulum

Question 32

What is the Stellate reticulum function

Answer 32

Hydrophilic, to help maintain space for developing crowns

Question 33

Which comes first? Dentine genesis or amelogenesis?

Answer 33

Dentinogenesis

Question 34

What differentiates into odontoblasts and ameloblasts

Answer 34

Dental papilla cells into odonto IEE into ameloblasts

Question 35

Enamel proteins

Answer 35

Enamelins Ameloblastins Amelogenins (90%)

Question 36

Describe secretory and maturation phase of amelogenesis

Answer 36

30% mineralised then 96% mineralised when matrix proteins are removed

Question 37

What is the epithelial attachment important for

Answer 37

Cells that generate junctional epithelium (hemidesmosomes)

Question 38

Which way does the nucleus migrate during the tome’s processes

Answer 38

Basally (tomes process at the apical side)

Question 39

Which direction does the cervical loop move in root formation

Answer 39

Apical

Question 40

HERS (hedwig epithelial root sheath)

Answer 40

2 layers (IEE AND EEE)

Question 41

Cell rests of malassez

Answer 41

Remnants when HERS degenerates No function but can cause cysts/Tumours

Question 42

What stimulates cementoblasts in root formation

Answer 42

When Ectomesenchyme cells comes in contact with dentine, differentiate into cementoblasts and starts producing cementum