embryology Flashcards
morula
solid mass of 32 cells formed from dividing zygote
zygote
fertilised ovum
blastocyst
outer layer of trophoblast cells, inner cell mass and blastocyst cavity
layers of bilaminar embryo
hypoblast and epiblasts
what is the function of the primitive streak
marks the start if gastrulation (process in which the inner cell mass is converted to the trilaminar embryo)
what are the three layers of the trilaminar embryo
ectoderm, mesoderm and endoderm (the three germ layers)
what is derived from the ectoderm
skin, mucous membranes, brain , spinal cord and tooth enamel
what is derived from the mesoderm
muscles , connective tissue, blood vessels, reproductive system
what is derived from the endoderm
alimentary system, respiratory system
what cells give rise to the ectomesynchyme layer
neural crest cells
what occurs during neurulation
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
what are the 5 steps in tooth development
1 - initiation 2 - morphogenesis 3 - cytodifferentiation 4 - matrix secretion 5 - root formation
what occurs during the initiation stage of tooth development
the primary epithelial band develops and divides to form the vestibular lamina and the dental lamina
what does the dental lamina give rise to
enamel organ
what does the vestibular lamina give rise to
buccal surfaces
what happens during the morphogenesis stage of tooth development
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
what occurs during the cytodifferentiation stage of tooth development
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)
what occurs during stage 4 of tooth development
enamel and dentine production begins
describe the process of that initiates enamel and dentine formation during tooth development
1 - dental papilla cells differentiate into ondontoblasts which lay down unmineralised dentine (predentine)
2 - dentine formation induces IEE cells to differentiate into ameloblasts
describe amelogenesis
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
how is the root shape defined
by the migration apically of the cervical loop which is now termed hertwigs epithelial root sheath
What does HERS induce
formation of root dentine (once 1st layer formed HERS breaks up)
Debris of mallasez
remnants of HERS
what do mesenchymal cells from the dental follicle develop into
cementoblasts
what germ layer is enamel derived from
ectoderm
what germ layer is the dental papilla derived from
ectomesenchyme (neural crest)
what germ layer is the dental follicle derived from
ectomesenchyme (neural crest)
what does the enamel organ give rise to
enamel
what does the dental papilla give rise to
dentine and pulp
what does the dental follicle give rise to
cementum , PDLs
where are pleuripotent stem cells found
in the three germ layers, they are slightly restricted
where are totipotent stem cells found
inner cell mass, can divide into anything
what period of pregnancy is most important for healthy development
first trimester
dentinogenesis imperfecta
teeth are discoloured due to incomplete dentine formation
gemination
one enamel organ sub divided into two giving the appearance of two teeth
hypodontia
reduced number of teeth
supernumerary
extra teeth
