embryology Flashcards

1
Q

morula

A

solid mass of 32 cells formed from dividing zygote

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2
Q

zygote

A

fertilised ovum

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3
Q

blastocyst

A

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

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4
Q

layers of bilaminar embryo

A

hypoblast and epiblasts

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5
Q

what is the function of the primitive streak

A

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

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6
Q

what are the three layers of the trilaminar embryo

A

ectoderm, mesoderm and endoderm (the three germ layers)

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7
Q

what is derived from the ectoderm

A

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

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8
Q

what is derived from the mesoderm

A

muscles , connective tissue, blood vessels, reproductive system

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9
Q

what is derived from the endoderm

A

alimentary system, respiratory system

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10
Q

what cells give rise to the ectomesynchyme layer

A

neural crest cells

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11
Q

what occurs during neurulation

A

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

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12
Q

what are the 5 steps in tooth development

A
1 - initiation 
2 - morphogenesis 
3 - cytodifferentiation 
4 - matrix secretion 
5 - root formation
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13
Q

what occurs during the initiation stage of tooth development

A

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

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14
Q

what does the dental lamina give rise to

A

enamel organ

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15
Q

what does the vestibular lamina give rise to

A

buccal surfaces

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16
Q

what happens during the morphogenesis stage of tooth development

A

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

17
Q

what occurs during the cytodifferentiation stage of tooth development

A

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)

18
Q

what occurs during stage 4 of tooth development

A

enamel and dentine production begins

19
Q

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

A

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

20
Q

describe amelogenesis

A

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

21
Q

how is the root shape defined

A

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

22
Q

What does HERS induce

A

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

23
Q

Debris of mallasez

A

remnants of HERS

24
Q

what do mesenchymal cells from the dental follicle develop into

A

cementoblasts

25
Q

what germ layer is enamel derived from

A

ectoderm

26
Q

what germ layer is the dental papilla derived from

A

ectomesenchyme (neural crest)

27
Q

what germ layer is the dental follicle derived from

A

ectomesenchyme (neural crest)

28
Q

what does the enamel organ give rise to

A

enamel

29
Q

what does the dental papilla give rise to

A

dentine and pulp

30
Q

what does the dental follicle give rise to

A

cementum , PDLs

31
Q

where are pleuripotent stem cells found

A

in the three germ layers, they are slightly restricted

32
Q

where are totipotent stem cells found

A

inner cell mass, can divide into anything

33
Q

what period of pregnancy is most important for healthy development

A

first trimester

34
Q

dentinogenesis imperfecta

A

teeth are discoloured due to incomplete dentine formation

35
Q

gemination

A

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

36
Q

hypodontia

A

reduced number of teeth

37
Q

supernumerary

A

extra teeth