Exam 1 Flashcards
what are the three stages of human development
-proliferation period
-embryonic period
-fetal development period
when does the proliferation period take place
0-3 weeks
when does the embryonic period take place
3-8 weeks
when does the fetal development period take place
9 weeks to term
what occurs during the proliferation period
-fertilization of ovum yields zygote
-mitotic cleavage of zygote forms blastomeres
-> or = to 32 blastomeres is called a morula
-64 cell stage called blastocyst
-blastocyst then developes inner cell mass and is called embryoblast
-embryoblast implants in uterine wall
fertilization of the ovum yields the
zygote
mitotic cleavage of the zygote forms the
blastomeres
more or equal to 32 blastomeres forms what
morula
the morula then develops into
blastocyst
at 64 cells it is called
blastocyst
why is a blastocyst called a blastocyst
morula develops an internal blastocystic cavity
what does the blastocyst become
embryoblast
what does the blastocyst develop to become the embryoblast
inner cell mass
when is the inner cell mass formed
days 6-7
Implantation of the embryoblast in the uterine wall begins and finishes when
begins at day 4 and is complete at day 10
The inner cell mass of the embryoblast transitions into what
bilaminar embryonic disc
what does the outer cell mass become
cytotrophoblast and syntrophoblast
what are the cytotrophoblast and syntrophoblast layers the precursor for
the placenta
what are the layers of the bilaminar embryonic disc
epiblast and hypoblast
what makes up the epiblast layer
ectoderm and mesoderm
what makes up the hypoblast layer
endoderm
name all 6 structures associated with the bilaminar embryonic disc
-epiblast layer
-hypoblast layer
-amniotic cavity
-blastocyst cavity
-syntrophoblasts
-cytotrophoblasts
enlargement of the amniotic cavity and migration of cells out of the hypoblast forms what
Heuser’s membrane
what will Heuser’s membrane form
the internal lining of the blastocyst cavity
once the Heuser’s membrane forms the internal lining of the blastocyst cavity, what is the blastocyst cavity called
the yolk sac
once the yolk sac has been formed, what are the cell layers
-epiblast
-embryonic mesoderm
-hypoblast
once the yolk sac has been formed, what are the embryonic cavities that are present
-amniotic
-yolk sac
-chorionic
During the 3rd week of development, the bilaminar disc is characterized by the formation of
-primitive streak
-Notochord
-Neural tube
Name the three distinct embryonic germ layers of the bilaminar disc during the 3rd week of development
-ectoderm
-mesoderm
-endoderm
what are the three parts of the primitive streak
-pit
-node
-groove
what is the development of the notochord
-primitive node -> notochordal process -> notochord
Describe the process of the formation of the notochord
-prenotochordal cells invaginate within the primitive node and migrate towards the cephalad until they reach the prechordal plate
-they then detach themselves from the ectodermal layer to line within the mesoderm forming the notochord
the ______ functions as a primitive skeletal support of the embryo around which the axial skeleton later forms
notochord
the notochord induces the formation of
somites
what are the precursors of the vertebral column, ribs, and associated back muscles and overlying dermis
somites
what is the notochord formed from
ectodermal cells from the primitive node
what are the three derivatives of mesoderm
-paraxial mesoderm
-intermediate mesoderm
-lateral plate mesoderm
what does paraxial mesoderm give rise to
somites
what does intermediate mesoderm give rise to
urogenital system
what does lateral plate mesoderm give rise to
-parietal mesoderm
-visceral mesoderm
what does parietal mesoderm become
mesothelial (serous) membranes that cover the peritoneal, pleural, and pericardial cavities
what does visceral mesoderm become
forms the thin serous membranes that cover individual organs EX) stomach, pancreas, spleen, etc
name the derivatives of ectoderm
-epidermis, hair and nails
-epithelium of oral and nasal cavities and paranasal sinuses
-salivary and endocrine glands
-nervous system
-enamel
what are derivatives of endoderm
GI tract epithelium and associated glands
Name 5 neural tube related developmental defects
-spina bifida
-meningocele
-meningomyelocele
-meningoencephocele
-anencephaly
what causes spina bifida
folic acid deficiency
what is meningocele
extrusion of dura and arachnoid mater
what is meningomyelocele
extrusion of neural tissue plus all 3 meninges
what is meningoencephalocele
extrusion of a ventricular cistern plus neural tissue
what is anencephaly
fatal defect characterized by lack of development of the cranium and brain
what are examples of mild defects of neural tube closure
spina bifida and meningocele
what are the intermediate defects of neural tube closure
-meningomyelocele
-meningohydroencephalocele (worse)
what is the fatal defect of neural tube closure
anencephaly
what is another name for neural crest cells
ectomesenchyme neuroectoderm
what 5 things make up the brachial/pharyngeal arches
-1st brachial groove
-1st brachial pouch
-2nd brachial pouch
-3rd brachial pouch
-4th brachial pouch
what does the 1st brachial groove form
external auditory canal
what does the 1st brachial pouch form
eustachian tube
what does the 2nd brachial pouch form
palatine tonsils
what does the 3rd brachial pouch form
inferior parathyroids and thymus
what does the 4th brachial pouch form
superior parathyroids and ultimobrachial body
what period of development are neural crest cells and the brachial/pharyngeal arches associated with
embryonic period
3-8 weeks
during what period of time does the growth of the babies body cath up to the growth of the head
fetal development
what are the four processes that make up the development of the face
-mandibular process
-maxillary process
-lateral nasal process
-median nasal process
what is the precursor for the oral cavity called in the embryo
stomodeum
defective fusion of what results in cleft lip
defective fusion of the median nasal process with the maxillary process
when do the median nasal process and maxillary process normally fuse
5-6 weeks of gestation
defective fusion of what results in cleft palate
defective fusion of the palatine shelves
when does fusion of the palatine shelves normally begin and reach completion
begins during 8th week and is completed by the 12th week
what percent of all clefts are combined cleft lip and palate
45% most common
what percent of clefts are isolated cleft palate
30%
what percent of clefts are isolated cleft lip
25% Least common
the incidence of cleft lip/palate is highest in what ethnicites
-chinese, japanese, native americans, and afroamericans
is cleft lip more common in white populations
no
if one child is born with cleft lip, there is a _____ chance of a second child exhibiting the same defect
40%
what are some known teratogens involved in congenital malformations
-drugs
ethanol, tetracycline, dilantin, lithium, methotrexate, warfarin, thiolidomide, androgens, progesterone, and retinoic acid
-chemicals
methylmercury, polychlorinated biphenyls
-radiation
where does a nasopalatine duct cyst develop
at the line of fusion between the palatine shelves and the primary plate
what occurs when a lateral cervical cyst/ brachial fistula forms
cervical sinus remains past the 7th week
what is the embryonic precursor associated with thyroid ectoderm and the anterior 2/3 of the tongue
brachial arch 1
what are the intermediate structures associated with brachial arch 1
-median tongue bud
-foramen cecum
-lateral lingual swellings
what is the intermediate structure associated with the 2nd brachial arch
copula/tuberculum impar
does the 2nd branchial arch give rise to an adult structure
yes but overgrown by the hypobranchial eminence
what is the intermediate structure associated with the 3rd brachial arch
hypobranchial eminence
what adult structure does the 3rd branchial arch give rise to
post 1/3 of tongue
what are the intermediate structures of the 4th branchial arch
minor contributions to the hypobranchial eminence
does the 4th branchial arch give rise to an adult structure
no
what cranial nerve is associated with branchial arch 1
trigeminal
sensory to ant 2/3 of tongue
what cranial nerve is associated with branchial arch 2
facial
special sensory (taste) to ant 2/3 via the chorda tympani branch
what cranial nerve is associated with branchial arch 3
glossopharyngeal
sensory to post 2/3 of tongue
what cranial nerve is associated with branchial arch 4
vagus
sensory to extreme post 1/3 via the superior laryngeal branch
what is the cranial nerve associated with branchial arch 6
hypoglossal
motor to all tongue muscles
what is median rhomboid glossitis
was thought to represent a portion of the tuberculum impar of branchial arch 2, now considered a result of a fungal infection
what causes a thyroglossal duct cyst
failure of thyroglossal duct to involute
located at midline of neck
what cartilage forms from branchial arch 1
-Merkels Cartilage
mandible
maleus
incus
what cartilage forms from branchial arch 2
-Reicharts cartilage
stapes
styloid process
stylohyoid ligament
lesser horn of hyoid
what cartilage forms from branchial arch 3
greater horn of hyoid
what cartilage forms form branchial arch 4
thyroid cartilage
how many hillocks lead to development of the ear
6
when does the ear develope
embryonic period
3-8 weeks
what tissues make up a tooth
-enamel
-dentin
-cementum
-pulp
what tissues make up peridontium
-gingiva
-PDL
-cementum
-alveolar bone
How many stages of tooth development are there
6
what are the 6 stages of tooth development
- initiation
- Bud stage
- Cap stage
- Bell stage
- Apposition
- Maturation
what occurs during the initiation stage of tooth development
cellular induction
what occurs during the bud stage of tooth development
cellular proliferation
what occurs during the cap stage of tooth development
proliferation, differentiation, and morphogenesis
what occurs during the bell stage of tooth development
proliferation, differentiation completed, and morphogenesis (can see all cell layers at this point)
what occurs during the apposition stage of tooth development
induction and proliferation
what occurs during the maturation stage of tooth development
maturation
Epithelium plays an instructional role during what stage of tooth development
pre-tooth bud stage
what specifies the dental nature of neural crest cells
epithelium
once neural crest cells fate has been determined to be tooth, they then specify what
tooth type and the nature of the product produced by the epithelium
Primitive oral ectoderm becomes what
enamel organ
what does the enamel organ differentiate into
-outer dental epithelium
-stellate reticulum
-stratum intermedium
-inner dental epithelium
what differentiates into ameloblasts
inner dental epithelium
in terms of tooth development, what do neural crest cells differentiate into
dental follicle and dental papilla
what does the dental follicle differentiate into
-PDL
-Cementum
-Alveolar bone
what does the dental papilla differentiate into
pulp
when does the induction stage take place
6-7 weeks
ectoderm invaginates into what
mesenchyme
describe the induction stage of tooth development
-ectoderm invaginates into mesenchyme and is now called the dental lamina
the dental lamina is separated from the surrounding mesenchyme by what
a basement membrane
when does the bud stage of development occur
8th week of development
describe the bud stage of tooth development
proliferating oral ectoderm make the transition into dental lamina
when is the early cap stage of tooth deveopment
9-10 week
at what stage of tooth development can you differantiate all layers of the enamel organ
bell stage
what is the function of cells of the outer enamal epithelium
protective barrier
what is the function of cells of the inner enamel epithelium
differentiate into ameloblasts
what is the function of cells of the stellate reticulum
supportive function in enamel production
what is the function of cells in the stratum intermedium
differentiate into cementum, PDL, and bone
what is the function of cells of the dental papilla
outer cells differentiate into odontoblasts and inner cells differentiate into pulp tissue
what is described as the junction of the outer and inner enamel epithelia
cervical loop
what is the site of cemento-enamel junction in the adult tooth
cervical loop
what is Hertwig’s Epithelial root sheath
the fusion and apical extension of the outer and inner enamel epithelia
what does Hertwig’s Epithelial root sheath determine
the outline of the root dentin and the number of roots a tooth will have
when is hertwig’s root sheath removed
before the cementum is laid down
where does enamel formation stop
at the termination of the enamel organ
dentin formation continues past the termination of the enamel organ and does what
pushes the tooth occlusally
when is root length completed
1-4 years after the tooth has erupted
what does stratum intermedium produce
alkaline phosphatase
what is the first formed dentin
mantle dentin
what does mantle dentin contain
type I and III collagen
collegen fibers in dentin matrix are oriented ________ to the DEJ
perpendicular
what does mantle dentin stimulate
ameloblasts
actively secreting ameloblasts are ________ __________ cells
tall columnar
inactive ameloblasts are _____ __________ or elongated cuboidal
short columnar
what is the primary cuticle
at the final stage of mineralization, the reduced ameloblasts with the remaining cells of the outer epithelium, stellate reticulum, and stratum intermedium form a membrane on the enamel
what is anodontia
total lack of tooth development
what is hypodontia
the lack of development of one or more teeth
what is oligodontia
the lack of development of 6 or more teeth
what is hyperdontia
the development of an increased number of teeth
what are extra teeth called
supernumerary teeth
when in tooth development do supernumerary teeth develope
a defect that originates in the initiation stage
what is the most common manifestation of supernumerary tooth formation
mesodens
what is an odontoma
growth of dental materials with no distinct aznatomy
when in tooth development does an odontoma form
during the initiation stage
what does an odontoma consist of
dentin, cementum, enamel
what is a complex odontoma
a conglomerate mass of enamel an dentin that bears no anatomic resemblance to a tooth
what is a compound odontoma
multiple small tooth like structures
what casues root abnormalities
an issue with the epithelial diaphragm in Hertwigs Root Sheath
what is taurodontism
an enlargement of the body and pulp chamber of multirooted teeth with apical displacement of the bifurcation
(very long root trunk and very short roots)
what is a dilaceration
an abnormal angulation or bend in the tooth root
what does gemination result in
a large single rooted tooth with one pulp cavity and exhibits twinning in the crown area
when in tooth formation does gemination occur
during the cap stage
what is the tooth count in the case of gemination
tooth count is normal when the double tooth is counted as one
what is the tooth count in fusion
refers to a double tooth in which the tooth count reveals a missing tooth when the double tooth is counted as one
what is concrescence
union of root structure of two or more teeth by cementum
when does concrescence occur
during the apposition and maturation stages
what is tubercule formation
a defect that results in an extra cusp due to effect on enamel organ
when does tubercule formation occur
during the cap stage
what is a dentigerous cyst
originates by separation of the dental follicle from the crown of the unerupted tooth
the cyst is attached at the CEJ
what type of cyst comprises 20% of all jaw cysts
dentigerous cysts
what does a odontogenic keratocyst arise from
cell rests of the dental lamina (rests of Serres)
OKC consist of _____ of all odontogenic cystst
3-11%
what age group is most diagnosed with OKC
10 and 40 years old make uo 60% of all cases
where are OKC found most commonly
65% in mandible
OKC are ______ ___________ cysts
bone expanding
locally invasive
OKCs located in the posterior mandible often present as
multilocular lesions
what is the tx for OKCs
surgical removal
what is the recurrence rate of OKCs
30%
describe the histology of an OKC
6-8 cell layer of SSE with parakeratosis at the luminal surface. lumen is often filled with keratin
what is the most common neoplastic lesion arising from odontogenic epithelium
ameloblastoma
describe the histology of an ameloblastoma
slow growing and locally invasive tumor
multilocular soap bubble appearancew
when looking at a radiograph of a ameloblastoma how will th etumor appear
multilocular
ameloblastomas are resistant to what form of tx
radio-resistant
is enamel cellular or acellular
acellular
does enamel have collagen in its matrix
no
how much harder than dentin is enamel
5x
what is the hardest tissue in the body
enamel
what is the stucture enamel is packaged into
ca HA crystals in enamel rods
what percentage mineral is enamel
96%
what percentage water is enamel
1%
what percentage of enamel is made up of organic components
3%
what protein constitutes 90% of protein in enamel
amelogenin
what makes up 5% of enamel proteins
enamelin
what enamel protein is found in enamel tufts at CEJ
tuftelin
what physical properties does amelogenin exhibit
thixotropic
what does thixotrophic mean
the ability to flow under pressure
what is the largest enamel protein
enamelin
where is enamelin restricted to
enamel rod areas
where is tuftelin restricted to
the DEJ in enamel tufts
what is thought to be the role of enamelin
plays a role in crystal growth and nucleation
what is thought to be the role of tuftelin
play a role in induction, the initiation of mineralization, and possibly functions as a junctional protein linking enamel and dentin
where is sheathlin found
througout the rod and interrod enamel
preferentially in the rod sheaths
neural crest cells induce the formation and proliferation of
the dental lamina
inner enamel epithelium induces the differentiation of
odontoblasts
what are the 5 stages of ameloblast function
- morphogenic stage
- differentiation stage
- secretory stage
- maturation stage
- protective stage
how many ameloblasts contribute to the compostion of one enamel rod
4
name the 7 structural features of enamel
-striae of Retzius
-Perikymata
-Hunter-Schreger bands
-Gnarled enamel\
-Enamel lamellae
-enamel tufts
-enamel spindle
what are striae of retzius
incremental lines produced by periodic constriction of tomes process associated with corresponding increase in the face forming the interrod enamel
cross striations on each rod represent _____ hours of enamel matrix production
24
what are perikymata
external manifestations of the striae of Retzius
what are Hunter Schregar bands
an optical phenomenon produced by changes in direction of enamel rods
what is gnarled enamel
enamel rods appear to be twisted in a complex arrangment
very resistant to fracture and abbrasion
where is gnarled enamel most commonly found
cusp tips
what is enamel lamellae
hypomineralized areas of enamel extending from the DEJ for considerable distnaces into the enamel
what may be involved in smooth surface caries
enamel lamellae
what is an enamel crack
cracks extending from the enamel surface to variable distances into the enamel
may extend into the dentin
what are enamel tufts
hypomineralized areas of enamel at the DEJ that are rich in enamelin and tuftelin
what are enamel spindles
extensions of odontoblastic processes and tubules across the basal lamina during tht inital stages of matrix formation
what is hypomineralization primarily related to
delay in the removal of amelogenin during maturation
birthing difficulties and nutritional deficiencies also commonly disturb development
what is hypoplasia of enamel generally induced by
infectious diseases of childhood
measles, rhematic fever, mumps
which leave a defect in the parts of the teeth activley developing at the time of infection
what is fluorosis
mottled enamel occurs as a result of a diet containing high levels of fluoride
what is amelogenesis imperfecta
defective enamel matrix deposition, which in turn voids the possibility of enamel mineralization
what is the more common type of amelogenesis imperfecta
autosomal dominant
what are enamel pearls and cervical enamel projections
defects that occur during the apposition and maturation stages due to displacement of ameloblasts to the root structure
what teeth are enamel pearls most often seen in
max molars
what teeth are CEPs most often involved in
mand molars
what is a dens in dente
a deep invagination of the crown or root that is lined with enamel
what tooth is most commonly affected by dens in dente
max incisor
what is the range of enamel thickness over the cusps
2-2.5 mm
what is the neonatal line
represents an exaggerated hypomineralized striae of retzius that forms at birth
what is another name for perikymata
imbrication lines of pickerill
what is the enamel cuticle composed of
remnants of the reduced enamel epithelium
what is the enamel pellicle comprised of
glycoprotein precipitates derived from saliva and or gengival crevicular fluid
