Tooth Anatomy and Histology Flashcards
1
Q
What are the different layers in the bell stage of tooth development? likely to come up
A
- Outer enamel epithelium
- inner enamel epithelium
- Stellate reticulum
- dental papilla
2
Q
what stage of tooth development does amelogenesis happen?
A
Bell stage
3
Q
What happens during primary tooth development?
A
- epithelium thickens
- grows down into mesenchyme
- fors a U shaped band.
4
Q
What happens during dental lamina formation of tooth development?
A
- primary epithelial divids into2
- grows deeper into the ectomesenchyme
- dental lamina begins to form
5
Q
What happens during the bud stage of tooth development?
A
- growing enamel organ
- ectomesenchyme undergoes proliferation surrounding the enamel organ
6
Q
What happens during the cap stage of tooth development?
A
- enamel organ enlarges
- development of the stellate reticulum
- outer enamel epithelium has cudoid cells
- inner enamel epithelium has columner cells
- mesenchymal cells for the dental follicle around the enamel organ
- dental papilla is formed with cells from mesenchyme.
7
Q
What happens during root development of tooth development?
A
- double layered epithelial root sheath is formed.
- root sheath encloses dental papilla and forms the future shape of the root, and forms the apical foramen.
- peripheral cell of root sheath of dental papilla form into odontoblasts
- dental follicle cells turn into cementoblasts and cememtogenesis starts
- remaining dental follicle cells become fibroblasts of the PDL
- collagen secreted by fibroblasts become embedded as sharpeys fibre into developing cementum and alveolor bone,
8
Q
what happens during the persecutory phase of amelogenesis? likely to come up
A
The ameloblasts elongate, change internally, reverse polarity and degrade the basal lamina
9
Q
what happens during the secretory phase of amelogenesis? likely to come up
A
further elongation, and the development of the Tomes process.
10
Q
what origin is enamel?
A
ectoderm
11
Q
where does enamel develop from?
A
the internal enamel epithelium of the tooth germ
12
Q
What does lamella in enamel look like?
A
it is a line though the tooth from the EDJ to the outer surface of enamel.
13
Q
What causes spindles in enamel and what do they look like?
A
they are small lines from the EDJ that are reminance of tooth development.
14
Q
What are the long period incremental lines in enamel called? likely to come up
A
Striae of Retzium (they are oblique and irregular)
15
Q
where are Striae of Retzium more frequently found?likely to come up
A
at the cervical margin
16
Q
Which bands in enamel formation show how enamel has been secreted?
A
Hunter-Schreger Bands
17
Q
why do Hunter-Schreger Bands occur in enamel?
A
because crystallites dont stay in a straight line because they are secreted at different rates from 2 different sites on the Tomes process
18
Q
why does carie follow Hunter-Schreger Bands ?
A
caries follows the path of less resistance.
19
Q
what is enamel composed of?
A
-95% inorganic- calcium hydroxyapatite crystals
-1-3% organic - ameloblastin, amelogenin
Emamelin
Tuftelin
- 2% water
20
Q
what is different about surface enamel compared with the rest of enamel?
A
- aprismatic
- crytalites are alligned parallel and at a right angle to the surface.
21
Q
why does enamel prisms have a distinct formation?
A
due to the 2 secretory site of the Tomes process.
22
Q
How does the EDJ prevent Fracturing/sheering?
A
- is scalloped to prevent cracking through the tooth.
- prisms close to it are parallel to avoid sheering.
23
Q
what is dentines origin?
A
ectomesenchyme
24
Q
where is dentine developed from?
A
the dental papilla of the tooth germ
25
Where is mantel dentine found and what is its purpose? *likely to come up*
- found closes to the EDJ
| - helps prevent small cracks developing in the enamel from going into the dentine.
26
what is different about mantle dentine when compared to other dentine? *likely to come up*
branching of tubules is perpendicular to EDJ
27
what causes interglobular dentine?
sin number of calcospherites not fused correctly with advancing mineralisation front.
28
what is the bulk of dentine called?
circumpulpal dentine
29
where is the hyaline layer in dentine found?
next to cementum.
30
where is pre-dentine found and what is it?
close to the pulp chamber and it is unmineralised dentine.
31
what causes sclerotic dentine?
tubules fill in as a response to an external stimulus.
32
what is the difference between sclerotic dentine and dead tracts?
sclerotic dentine appears transparent and fill in.
| dead tracts stay air filled caused by primary odontoblasts bring killed by an external stimulus.
33
what are daily incremental lines in dentine called?
von ebner lines
34
what are weekly incremental lines in dentine called?
Andresen lines
35
what are the schreger lines in dentine?
primary curvatures of the dentinal tubules.
36
where are the contour lines of owen found and what are they?
- in dentine
| - secondary curvatures of the dentinal tubules.
37
why does secondary dentine develop?
because it has a slow rate of development through time.
38
why does tertiary dentine form?
- response to an external stimulus (caries, altrition, preps, trauma)
- creates a restriction to area beneath irritation.
39
In tertiary dentine why are there 2 different types?
Reactionary dentine: response to insult, odontoblast damage/death causing an irregular appearance.
Reparative dentine : 'odontoblast-like' cells form as originals where destroyed causing very irregular calcified tissue.
40
what is the difference between enamel and dentine hydroxyapatite crystals?
once found in dentine are alot smaller
41
what make up the composition of dentine?
- 65%-70% inorganic : hydroxyapatite crystals
- 20% organic matrix : Type 1 Collagen
- 10 % water
42
how does dentines composition aid in its resistance to fracturing?
makes it rigid, elastic and not brittle.
43
Is enamel or dentine a vital tissue? and why?
Dentine is vital due to the presence of odontoblasts.
44
what happens to dentine tubules as we mature?
peritubular dentine is deposited on the walls narrowing the lumen.
45
where would you find extracellular dentinal fluid?
in the peri-odontoblastic space in dentine.
46
what do odontoblasts do?
they lay down extracellular collagen matrix
47
what causes dentine sensitivity?
Hydrodynamics (fluid flow)
48
what is peritubular dentine? *likely to come up*
- small crystals in a non-fibrous matrix.
| - line dental tubules.
49
why do dentinal tubules have narrower lumen closer towards the EDJ? *likely to come up*
due to depositing of peritubular dentine.
50
what are the stages of hydrodynamics? *likely to come up*
- stimulus triggers a flow of fluid within the tubules.
- this depolarises nerve endings in the inner part of the tubule/between odontoblasts at pulp-predentine junction.
- message sent to subodontoblastic neural plexus.
51
what is the origin of cementum?
ectomesenchyme (neural crest)
52
where is cementum developed from?
the mesenchymal cells of the inner layer of the dental follicle.
53
what is the composition of cementum?
- 65% inorganic - hysroxyapatite
- 23% organic - collagen type 1
- 12% water
54
is cementum vital or not vital and why?
vital because it contains cementoblasts and cementocytes.
55
how is cementum different from bone?
it has no blood vessels and is readily resorbed allowing for movement.
56
what types of collagen fibres are found in cementum?
- Sharpeys fibres (extrinsic)
| - cementoblast fibres (intrinsic)
57
where would you find cementoblasts and what is their function?
- they are found in the PDL on the boarder to cementum.
| - they produce cementum matrix.
58
what causes afibrillar cementum?
-reduced enamel epithelium (which overlies and protects the cervical enamel in unerupted teeth) - allowing cells of the dental follicle to come in contact with the enamel surface, they are then induced to form cementoblasts.
59
where would you find cementocytes?
in cellular cementum
60
what are the unevenly spaced incremental lines in cementum called?
lines of salter
61
Are sharpeys fibres mineralised in cementum or in the PDL?
in cementum.
62
what is the layer of uncalcified cementum matrix called?
precementum
63
through what layer of dentine does cementum attach via fibrils?
Hyaline layer
64
What is the difference between intrinsic fibres and sharpeys fibres in cementum?
Intrinsic fibres do not aid in attachment.
65
what would cause a reversal line in cementum?
small area of resorption, caused by micro trauma, (carried out by multinucleated odontoclasts). then filled in by deposition of mineralised tissue.
The reveal line separating repair tissue and normal underlying tissue.
66
what type of cementum is created first? and what one second?
Acellular is first
| Cellular is second.
67
what are the main differences between acellular and cellular?
acellular:
- No cells
- slow rate of development
- incremental lines are close together
- covers the whole root.
Cellular:
- contains cementocytes
- fast rate of development
- incremental lines are wide apart and irregular
- mostly at and around apex and over the top of acellular.
68
How is acellular cementum formed?
mesenchymal cells of the inner layer of the dental follicle lie close to the newly formed pre-dentine and turn into cementoblast-like cells - they secrete collagen fibrils and form acellular cementum.
69
where does acellular extrinsic fibre cementum get its collagen from? and where is it found?
- all collagen is as sharpeys fibres from PDL
| - mainly over cervical 1/2 of root.
70
How is cellular cementum formed?
Over time
71
what origin is the PDL from?
ectomesenchyme (neural crest)
72
where does the PDL develop from?
from the dental follicle
73
what are oxytalan fibres? and where are they found?
- immature elastin fibres that are found in the PDL
| - aid in fibroblast migration
74
what is the purpose of the Lamina propia?
inserts into tooth and bone with its fibres, acting together with tissue fluid to support free gingiva and hold attached gingiva
75
where is basal lamina deposited and how does it attach?
- deposited on enamel surface
| - cells attach via hemidesmosomes
76
what cells produce sharpeys fibres?
fibroblasts
77
where are the most sharpeys fibres found acellular or cellular cementum?
acellular
78
what is different between sharpeys fibres in bone compared to in cementum?
in bone they are fewer but larger.
79
what are the ruminants of the epitherlail root sheath of Hertwig in the PDL called?
Epithelial cell rests of Malassez
80
where are Dentoalveolar crest fibres in the PDL found?
closest to the lamina propia
81
where are horozontal fibres in the PDL found?
half way down the root where the bone and tooth are parallel.
82
where are apical fibres in the PDL found?
at the apex of the root.
83
where are interradicular fibres in the PDL found?
in-between the roots of a multi-rooted tooth.
84
where are oblique fibres in the PDL found?
at the lower half of the the root.
85
Where do you find Fibroblasts ?
PDL
86
what is the role of fibroblasts?
responsible for synthesis and degradation of collagen by a 'phagoxytic process' and for the secretion of all components of the PDL ground substance.
87
what are principal fibres?
extracellular matrix fibres gathered together to make a bundle.
88
where are alveolar arteries/capillaries found? and what is their purpose within the PDL?
- have origin in the inta-boney spaces. and form a plexus around the tooth.
- give a rich blood supply allowing the PDL to function after endo tx.
89
what are the channels through the socket wall that carry blood vessels called?
Volkmanns cancels.
90
What are the only Type 2 collagen fibres in the PDL? and what is their purpose?
- Reticulin fibres
| - they are a cross link + form meshwork to aid in support
91
what is the purpose of ground substand found in between fibred of the PDL?
binds water, controls collagen fibrillogenesis and orientation and binds growth factors.
92
what are the stages of collagen fibre formation?
- after cementogenesis has begun.
- cells of remaining dental follicle become obliquely oriented along root surface and become fibroblasts of the PDL
- fibroblasts secrete collagen into extracellular area - this then becomes sharpeys fibres in developing cementum and bone.
93
what purpose do collagen fibred have when arranged into principle fibre bundles?
- allow for a 'visco-elastic' response to axial loading.
| - give support
94
what is the cell that resorbs bone called? and what features do they have to do this?
- osteoclast
- many microvilli for degradation
- secrete protons to lower pH to dissolve mineral phase of bone.
- degrade organic matrix with enzymes.
95
where are Osteocytes found? and what is their purpose?
- trapped osteoblasts trapped in bone matrix.
| - induce osteoclast activation and are the primary mechano-sensors in bone (detecting stain)
96
What cells secrete and mineralise osteoid matrix ?
Osteoblasts
97
what are the functions of osteoblasts?
- secrete and mineralise osteoid matrix
| - contoling influence in activity of osteoclasts.
98
what are Lamellae?
layers of deposited bone
99
what is the composition of alveolar bone?
- 60% inorganic - hydroxyapatit crystals.
- 25% organic - mostly type 1 collagen
- 15% water
100
what is osteoid?
- newly deposited, unmineralised bone matrix.
- produced by osteoblasts.
- type 1 collagen fibrils enbedded in complex ground substance.
101
what lines in bone mark the former surface of bone depositation?
resting/mineralisation lines.
102
what is different about reversal lines, and why are they formed?
- irregular and scalloped
| - marks where bone has been resorbed and then reversed to formation.
103
what are the 2 different types of bone?
- Compact bone
| - Cancellous bone
104
what is the difference between Compact bone and Cancellous bone ?
- Compact bone: dense solid mass - lamellae arranged into harversian system and circumferential lamellae
- Cancellous bone - lattice arrangement of the individual bony trabeculae that surround marrow.
105
what is the harverian system?
- central canals and upto 20 concetric lamellae.
106
why is circumferential lamellae formed?
following remodelling.
107
What are the stages of the bone remodelling cycle?
- Resorption
- Reversal
- Formation
- Resting
108
what is the structure of salivary glands?
compouint tubulo-acinar structure.
109
what can be found in the septa between lobes of a salivary gland?
blood vessels, nerves and collecting ducts.
110
What are the 6 functions of salivary glands?
- digestion
- antibacterial
- mineral protection
- lubrication
- taste
- hormone production.
111
what is the composition of salvia?
over 99% water
| under 1% inorganic= organic compound.
112
where are minor salivary glands found?
- mocosa of lip
- cheek
- hard/soft palate
- tongue.
113
do minor salivary glands secrete mucous or serous saliva? and what is the one exception to this rule?
they normally secrete musous.
| - Glands of Von Ebner found on the tongue under the circumvallate papillae secretes serous saliva.
114
what are the differences between mucous and serous secretions?
- mucous : viscous, mucin-rich containing proteins.
| - Serous: watery, protein rich fluid.
115
what are the differences between mucous and serous acini?
- mucous : tubes rather than spheres, form their own duct system with no intercalated or striated ducts. have a 'cap' of serous secreting cells (serous demilune)
- Serous: globe shaped structure - made from many secreting cells that empty into a intercalated duct.
116
How does saliva travel from the serous acinus to the secretory duct?
into a intercalated duct, then this emptys into a striated duct (where active exchange occurs) then into a secretory duct.
117
do the parasympathetic or sympathetic fibres of the automic nervous system innervate the acinic in major salivary glands to secrete?
both.
118
do the parasympathetic or sympathetic fibres of the automic nervous system innervate the acinic in minor salivary glands to secrete?
parasympathetic
119
why is saliva isotonic in the acinus and then hypertonic in the secretory ducts?
when saliva passes through the striated ducts, sodium chloride and bicarbonate is removed turning it hypertonic.
120
what saliva is produced by the parotid gland?
100% serous and hypertonic
121
where is the parotid gland found?
on the sides of the face around ear level.
122
is the parotid gland a spontaneous secretor?
no - its nonspontaneous.
123
what saliva is produced by the sublingual gland?
1:10 Serous:mucous
| isotonic (due to having no striated ducts)
124
where is the sublingual gland found?
under the tongue.
125
is the sublingual gland a spontaneous secretor?
yes
126
what saliva is produced by the submandibular gland?
10:1 Serous:mucous
| hypertonic
127
where is the submandibular gland found?
under your chin.
128
is the submandibular gland a spontaneous secretor?
no -its nonspontaneous.
129
what gland has more ducts the parotid or submandibular? and why?
Parotid has more because the submandibular has mucous cells rather than all serous.
