embryology

Question 1

morula

Answer 1

solid mass of 32 cells formed from dividing zygote

Question 2

zygote

Answer 2

fertilised ovum

Question 3

blastocyst

Answer 3

outer layer of trophoblast cells, inner cell mass and blastocyst cavity

Question 4

layers of bilaminar embryo

Answer 4

hypoblast and epiblasts

Question 5

what is the function of the primitive streak

Answer 5

marks the start if gastrulation (process in which the inner cell mass is converted to the trilaminar embryo)

Question 6

what are the three layers of the trilaminar embryo

Answer 6

ectoderm, mesoderm and endoderm (the three germ layers)

Question 7

what is derived from the ectoderm

Answer 7

skin, mucous membranes, brain , spinal cord and tooth enamel

Question 8

what is derived from the mesoderm

Answer 8

muscles , connective tissue, blood vessels, reproductive system

Question 9

what is derived from the endoderm

Answer 9

alimentary system, respiratory system

Question 10

what cells give rise to the ectomesynchyme layer

Answer 10

neural crest cells

Question 11

what occurs during neurulation

Answer 11

thickening of the ectoderm sees the formation of the neural plate, neural plate dives into mesoderm forming the neural tube, cells break off during this process and these are the neural crest cells

Question 12

what are the 5 steps in tooth development

Answer 12

1 - initiation 
2 - morphogenesis 
3 - cytodifferentiation 
4 - matrix secretion 
5 - root formation

Question 13

what occurs during the initiation stage of tooth development

Answer 13

the primary epithelial band develops and divides to form the vestibular lamina and the dental lamina

Question 14

what does the dental lamina give rise to

Answer 14

enamel organ

Question 15

what does the vestibular lamina give rise to

Answer 15

buccal surfaces

Question 16

what happens during the morphogenesis stage of tooth development

Answer 16

1 - dental lamina thickens into bud stage, ectomesenchymal condensation appears as dental papilla
2 - enamel organ forms a cap over the dental papilla. ‘cap’ stage organ has internal and external enamel epithelium which meet at the cervical loop

Question 17

what occurs during the cytodifferentiation stage of tooth development

Answer 17

sees the formation of the ‘bell’ stage enamel organ and the tooth shape being defined.
this stage of enamel organ has 4 layers - internal and external enamel epithelium , stellate reticulum and the stratum intermedium (inbertween IEE and SR)

Question 18

what occurs during stage 4 of tooth development

Answer 18

enamel and dentine production begins

Question 19

describe the process of that initiates enamel and dentine formation during tooth development

Answer 19

1 - dental papilla cells differentiate into ondontoblasts which lay down unmineralised dentine (predentine)
2 - dentine formation induces IEE cells to differentiate into ameloblasts

Question 20

describe amelogenesis

Answer 20

1 - dentine induces IEE cells to differentiate into ameloblasts
2 - ameloblasts synthesise and secrete enamel matrix proteins
3 - maturation phase - most proteins removed and mineral content increases
4 - protection phase - ameloblasts regress to form a protective layer that is involved in tooth eruption

Question 21

how is the root shape defined

Answer 21

by the migration apically of the cervical loop which is now termed hertwigs epithelial root sheath

Question 22

What does HERS induce

Answer 22

formation of root dentine (once 1st layer formed HERS breaks up)

Question 23

Debris of mallasez

Answer 23

remnants of HERS

Question 24

what do mesenchymal cells from the dental follicle develop into

Answer 24

cementoblasts

Question 25

what germ layer is enamel derived from

Answer 25

ectoderm

Question 26

what germ layer is the dental papilla derived from

Answer 26

ectomesenchyme (neural crest)

Question 27

what germ layer is the dental follicle derived from

Answer 27

ectomesenchyme (neural crest)

Question 28

what does the enamel organ give rise to

Answer 28

enamel

Question 29

what does the dental papilla give rise to

Answer 29

dentine and pulp

Question 30

what does the dental follicle give rise to

Answer 30

cementum , PDLs

Question 31

where are pleuripotent stem cells found

Answer 31

in the three germ layers, they are slightly restricted

Question 32

where are totipotent stem cells found

Answer 32

inner cell mass, can divide into anything

Question 33

what period of pregnancy is most important for healthy development

Answer 33

first trimester

Question 34

dentinogenesis imperfecta

Answer 34

teeth are discoloured due to incomplete dentine formation

Question 35

gemination

Answer 35

one enamel organ sub divided into two giving the appearance of two teeth

Question 36

hypodontia

Answer 36

reduced number of teeth

Question 37

supernumerary

Answer 37

extra teeth