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BAMS > Oral Morphology > Flashcards

Oral Morphology Flashcards

1
Q

What is cementum?

A

Covers root dentine
Made of collagen matrix and lamellar arrangement
Provides attachment for some periodontal fibres

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2
Q

What cell creates cementum?

A

Cementocytes

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3
Q

What are two types of cementum?

A

Cellular - contains cementocytes, later formed, present in apical part of root and in furcation regions
Acellular - adjacent to dentine, first formed

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4
Q

What is the alternative classification of cementum?

A

Acellular extrinsic fibre cementum - collagen fibres from PDL (sharpey’s fibres)

Cellular intrinsic fibre cementum - no sharpeys fibres, no role in tooth attachment

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5
Q

What are the 3 primary embryonic layers?

A

Ectoderm
Mesoderm
Endoderm

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6
Q

What is enamel derived from?

A

Ectoderm

All other parts of teeth and supporting structure derived from ectomesenchyme

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7
Q

What is the ectomesenchyme?

A

Part of the ‘neural crest’ that develops beside the primitive nervous system (ectoderm)

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8
Q

Besides enamel, what does the ectoderm differentiate into?

A 
Nervous system (spine, peripheral nerves and brain)
Epidermis
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9
Q

What do teeth develop from?

A

Tooth Germs

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10
Q

What is considered as the ‘fourth’ cell type?

A

Neural crest - forms between the ectoderm and the neural tube, the neural crest tissue is also called ectomesenchyme

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11
Q

What are the stages of tooth development?

A 
Initiation
Morphogenesis
Cytodifferentiation
Matrix Secretion 
Root formation
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12
Q

What is a stomodaeum?

A

Oral cavity of an embryo

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13
Q

When does tooth initation occur?

A

5-6 weeks in human embryo
Primary epithelial band develops at 6 weeks
Appears as thickening in epithelium of stomodaeum

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14
Q

What does the PEB split into?

A

Approx 7 weeks
Dental lamina - forms enamel
Vestibular lamina - forms buccal sulcus

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15
Q

When and where do tooth germs appear?

A

Approx 8 weeks,

Dental lamina

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16
Q

What are the two stages of morphogenesis?

A

Bud and Cap stages

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17
Q

What occurs in the bud stage of morphogenesis?

A

Approx 8-10 wks
Dental lamina thickens into a ‘bud’ enamel organ
Ectomesenchymal condensation appears - dental papilla

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18
Q

What occurs in the cap stage of morphogenesis?

A 
Approx 11 wks
Enamel organ forms a 'cap' over the papilla
'Cap stage' enamel organ made up of
- external enamel epithelium
- internal enamel epithelium
These both meet at cervical loop
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19
Q

What occurs during cytodifferentiation?

A

‘bell’ stage
approx 14wks
More cell layers differentiated
Tooth shape is being defined

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20
Q

What are the 4 layers of the ‘bell stage’ enamel organ?

A

Stellate reticulum
Stratum intermedium
Internal enamel epithelium
External enamel epithelium

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21
Q

What occurs in the 12th week of tooth embryology?

A

An extension appears on the lingual side of the dental lamina

This is the dental lamina for the permanent successor

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22
Q

What occurs in the 16th week of tooth embryology?

A

1st permanent molar germ develops as a backwards extension of the dental lamina

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23
Q

What occurs in the late bell stage?

A

Approx 18 wks
Late bell stage enamel organ
Crown shape is well defined (crown stage EO)
Apposition of enamel and dentine begins

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24
Q

How does dentinogenesis occur?

A

IEE differentiates to odontoblasts
Deposition of dentine matrix by odontoblasts(mainly collagen)
This unmineralised dentine is predentine
Mineralisation of dentine (hydroxyapatite)

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25
Q

What are the two stages of enamel formation?

A
  • Protein matrix deposition

- Organic component removal and mineralisation (‘maturation’)

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26
Q

What occurs during ameloblast differentiation of amelogenesis?

A

Dentine induces IEE cells to differentiate into ameloblasts

They elongate, becoming columnar and nucleus migrates to basal end

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27
Q

What occurs during secretory phase of amelogenesis?

A

Ameloblasts become secretory cells
They synthesise and secrete the enamel matrix proteins (amelogenins)
The matrix is then partially mineralised (30%)

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28
Q

What occurs during the maturation phase of amelogenesis?

A

Most of the matrix proteins are removed
Mineral content of enamel is increased
Mature enamel is 95% mineral

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29
Q

What occurs during the protection phase of amelogenesis?

A

Ameloblasts regress to form a protective layer - the reduced enamel epithelium

Involved in eruption
Formation of epithelial attachment

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30
Q

How is the root of a tooth formed?

A

HERS grows apically
HERS induces formation of root dentine
HERS then breaks up and persists as debris of Malassez
Mesenchymal cells from the follicle contact the dentine and differentiate into cementoblasts
These form cementum
Fibres from the developing PDL are embedded into the cementum (sharpeys fibres)

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31
Q

What is dentine?

A

Forms bulk of teeth
Harder than bone and cementum but not enamel
Greater compressive and tensile strength compared with enamel
Permeable; contains tubules
Contains cell processes
Yellowish in colour

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32
Q

What does dentine consist of?

A

Hydroxyapatite - 70% weight, 50% volume

Water - 10% weight, 20% volume

Organic matter - 20% weight, 30% volume

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33
Q

What are the contents of dentinal tubules?

A

Odontoblast process
Unmyelinated nerve terminals (sensory)
Dendritic cells
Dentinal fluid (ECF) from pulp

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34
Q

What does dental pulp contain?

A
  • Connective tissue
  • Cells - odontoblasts, fibroblasts, defence cells
  • Extracellular components- fibres, matrix
  • Nerves
  • Blood vessels
  • Lymphatics
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35
Q

What is the function of dental pulp?

A
  • Nutritive
  • Dentine growth
  • Dentine repair
  • Defence
  • Neural - sensory, control of dentinogenesis
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36
Q

What is a morula?

A

4-6 days

Solid mass of cells

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37
Q

What is a blastocyst

A

6-10 days
A hollow ball of cells:
- Inner cell mass
- Trophoblast

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38
Q

What is a zygote?

A

Fertilised ovum - begins as single cell but rapidly divides into morula

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39
Q

What does the placenta do?

A

It is the embryo’s life support

Baby’s blood is replenished from the mother’s blood - circulations dont mix, seperated by a thin barrier

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40
Q

What is the bilaminar embryo?

A

At approx 10-12 days, the implanted trophoblast contains an embryo, which has 2 cell layers

  • Epiblast - embryonic ectoderm, mesoderm and endoderm
  • Hypoblast - endoderm and extraembryonic mesoderm
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41
Q

What is the difference between identica; and fraternal twins in the blastocyst?

A

Identical twins have a divided inner cell mass

Fraternal twins have two blastocysts

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42
Q

What occurs during gastrulation?

A

The embryo develops

  • an axis
  • formation of a groove - primitive streak
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43
Q

How are the mesoderm and endoderm formed?

A

Some ectodermal cells from the epiblast are induced to differentiate and migrate through the primitive streak, towards the hypoblast, these new cells are the mesoderm.

A ‘not so clear’ interaction between the newly formed mesoderm and hypoblast forms the endoderm.

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44
Q

How is the trilaminar embryo formed?

A

Mesodermal cells push through the primitive streak and spread out to form a third layer.

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45
Q

When does organogenesis occur?

A

Weeks 3-8, organs develop from the 3 basic germ cell layers

CNS one of first - formation of neural groove (approx 20 days)

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46
Q

What is spina bifida?

A

Persistance of the neural groove - neural groove should form the neural tube in production of the CNS

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47
Q

How does the trilaminar embryo begin to take shape?

A

Front and back ends begin to fold under the middle

The embryo folds round the yolk sac and some important organs appear - heart, liver, lungs

48
Q

When is the embryo considered a foetus?

A

9 weeks

49
Q

Where are embryonic stem cells found?

A
  • Inner cell mass (‘totipotent’)

- Cells in 3 germ cell layers (‘pluripotent’)

50
Q

Where are adult stem cells found?

A

Committed cell lines e.g. bone marrow stem cells

51
Q

What does the ectoderm give rise to?

A

Skin
Mucous membranes of mouth and anus
Brain, spinal cord
Tooth enamel

52
Q

What does the mesoderm give rise to?

A 
Most connective tissues - dermis, tendons, cartilage, bone
Muscle
Blood vessels
Kidney/Urinary system
Reproductive system
Serous membranes
53
Q

What does the endoderm give rise to?

A

Alimentary canal (pharynx-rectum)
Respiratory system
Parts of urogenital system

54
Q

What does ectomesenchyme give rise to?

A 
Peripheral NS - sensory/autonomic
Melanocytes in skin
Adrenal medulla
Mesenchyme in head
Dentine, cementum, pulp, PDL, Jaw, bones
55
Q

What is the periodontal ligament?

A

A connective tissue, containing:

  • Cells
  • ECM
  • Fibres
  • Nerves
  • Blood vessels
56
Q

What does the periodontal ligament matrix consist of?

A
  • Hyaluronate glycosaminoglycans
  • Proteoglycans
  • Glycoproteins

Behaves as a viscous elastic gel

57
Q

What are the cells of the PDL?

A 
Fibroblasts
Cementoblasts
Osteoclasts and cementoclasts
Epithelial cells
Defence cells
58
Q

What nerves/receptors do the PDL contain?

A

Sensory - mechanoreceptors, nociceptors

Autonomic (SNS) - blood vessel control, vasoconstriction

59
Q

What are the periodontal fibres?

A

True periodontal ligament - fibres connecting tooth to alveolar bone

‘Gingival’ ligament - fibres mainly above the alveolar crest, including ‘free gingival’ fibres

60
Q

What is the purpose of the PDL?

A

Attaches tooth to jaw

Transmits biting forces to alveolar bone

61
Q

What are the alveolo-dental ligament fibres?

A 
Alveolar crest
Horizontal
Oblique
Apical
Inter-radicular (multi-rooted teeth)
62
Q

What are the interdental ligament fibres?

A

Trans-septal

63
Q

What is the function of the oral mucosa?

A 
Protection
Sensation
Secretion
Absorption
(Thermoregulation)
64
Q

What are the types of oral mucosa in the mouth?

A

Gustatory - tongue
Masticatory - gingiva
Lining

65
Q

What are the characteristics of masticatory mucosa?

A

(para) keratinised
Thick lamina propria (mucoperiosteum)

Subjected to friction, compression

66
Q

What are the characteristics of lining mucosa?

A

Mobile and distensible
Non-keratinised
Loose lamina propria and wide submucosa
More rapid turnover than masticatory mucosa

67
Q

What are the characteristics of gustatory mucosa?

A

Similar to masticatory
Keratinised
Present only on dorsum of tongue
Caracterised by papillae, some bearing taste buds

68
Q

What is the structure on mucosa?

A

Epithelium
Lamina propria
Submucosa
Bone

69
Q

What are the cell layers of the epithelium?

A

Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum germinativum

70
Q

What are examples of non-keratinocytes?

A

Melanocytes
Merkel cells
Langerhans cells - (dendritic cells)

71
Q

What type of epithelium is in the oral cavity?

A

Stratified squamous

72
Q

What are the 3 types of papillae present in gustatory mucosa?

A

Vallate
Filliform
Fungiform

73
Q

Histologically how do you identify sebaceous or salivary glands?

A

Salivary gland subsections much larger

74
Q

What is geographical tongue?

A 
Irregular, smooth patches
No FILIFORM papillae
Red/white margins
Asymptomatic - some ppl have discomfort
No Tx usually required
75
Q

What are the functions of oral fluids?

A

Protective

Digestive

76
Q

What are the three major salivary glands?

A

Parotid - serous
Submandibular - mixed
Sublingual - mucous

77
Q

What are the minor salivary glands?

A

Buccal (cheek) - mucous
Labial (lip) - mucous
Lingual (tongue) - mixed
Palatal (hard and soft palate) - mucous

78
Q

What is the structure of a salivary gland?

A

Secretory units exist within the acinus

Secretory units supplied by ducts (intercalated, striated, collecting)

79
Q

What is gingival crevicular fluid?

A

Fluid from epithelium lining the gingival crevice (sulcus), flow increases with inflammation

80
Q

When is salivary flow rates the lowest and highest?

A

Lowest - sleeping

Highest - eating

81
Q

What salivary gland contributes most when asleep?

A

Submandibular (70%)
No parotid
Equal sublingual (15%) and minor glands (15%)

82
Q

What salivary gland contributes most when stimulated?

A

Parotid (50%)
Closely followed by submandibular (40%)
Minor glands 8%
Sublingual 2 %

83
Q

What factors affect unstimulated salivary flow rate?

A 
State of hydration 
Previous stimulation
Circadian rhythm 
Circannual rhythms
Medications
Salivary gland disease
84
Q

What is the composition of saliva?

A

Inorganic - water (99.5%), Ions (0.2%)

Organic - Mainly proteins (0.3%)

85
Q

What is the function of fluoride in saliva?

A

Antibacterial
Forms fluoroapatite
Promotes remineralisation

86
Q

What is the function of calcium and phosphate in saliva?

A

Remineralisation

87
Q

What is the function of thiocyanate in saliva?

A

Antibacterial

88
Q

What is the function of bicarbonate/phosphates in saliva?

A

Buffering - effective at high flow rates, when HCO3 is highest

Phosphates - important ‘at rest’

89
Q

How is saliva secreted?

A

Through a chloride shift causing osmotic diffusion of water

90
Q

What is the function of salivary amylase?

A

Hydrolyses 1-4 alpha starch glycosidic links to maltose, maltotriose and alpha limit dextrins

91
Q

What is the function of salivary lysozymes?

A

Non-specific defence

Attacks bonds in bacterial cell walls causing lysis

92
Q

What is the function of salivary lactoperoxidase?

A

Enzyme which allows oxidation of thiocyanate to hypothiocyanate which is antibacterial

93
Q

What is the function of salivary cystatins?

A

Antimicrobial - Inhibits cysteine proteases

94
Q

What is the function of salivary gustin?

A

Activates taste buds

Potent PDE 5 activator

95
Q

What is the function of salivary histatins?

A

Histidine-rich proteins
Inhibit CaPO4 precipitiation - antimicrobial

Inhibits:
C. albicans
S. mutans

96
Q

What is the function of salivary immunoglobulins?

A

Secretory IgA
Specific immunity against bacteria
Vaccine vs S.mutans

97
Q

What is the function of salivary lacotferrin?

A

Iron-binding protein
Binds Fe3+
Antibacterial

98
Q

What is the function of salivary lipase?

A

From von Ebner glands on tongue

Hydrolyses triglycerides

99
Q

What is the function of salivary mucins?

A

Binds to tooth and epithelium for protective role, lubricant and component of primary pellicle

Affects bacterial adhesion

Promotes bacterial aggregation making it easier to clear from mouth

100
Q

What is the function of salivary statherins?

A

Anticalculus action

101
Q

What are examples of unconditioned salivary stimuli?

A

Mechanical - pressure on PDL/oral mucosa

Chemical - gustation, olfaction, common chemical sense

102
Q

What is the most potent chemical type to receptors on taste buds?

A

Acid > umami = salt > sweet > bitter

103
Q

What are examples of conditioned salivary stimuli?

A

Learned responses to
‘Psychic’ stimuli (thinking about food)
Visual stimuli
Auditory stimuli

104
Q

How is saliva secretion controlled?

A

PNS - Increase secretion and increased blood flow

SNS - Increase secretion and decrease blood flow

105
Q

What is the 2-stage mechanism of saliva secretion?

A

Primary secretion in acinus

Secondary modification in ducts

106
Q

What occurs during ductal modification?

A

Primary saliva modified as it passes through striated ducts
Reabsorption of sodium and chloride
Secretion of potassium and bicarbonate
Final saliva is hypotonic to plasma

107
Q

What is clearance?

A

Refers to the rate at which substances are removed from the mouth

108
Q

What is the importance of clearance?

A
  • Removal of harmful substances increased by high salivary flow rates (rapid clearance)
  • Retention of ‘beneficial’ substances is improved by low salivary flow rates (slow clearance)

Thus topical F- preparations should be tasteless and tablets should be sucked, not chewed

109
Q

What is the stephan curve?

A

A graph of plaque pH change over time

110
Q

How does gum work to decrease plaque?

A

It increases salivary flow and will neutralise acid created from plaque by increased bicarbonate content of saliva

111
Q

What are the categories of alternative ‘sugar-free’ sweeteners?

A

Bulk caloric (sucrose)/low caloric (mannitol) sweeteners

Non-calorie, high-intensity sweeteners (aspartamate)

112
Q

What is xerostomia?

A

When salivary flow rates fall below 50% of normal levels

Such reductions require loss of function of more than one major salivary gland

113
Q

What can cause decreased salivary flow?

A

Side effects of drugs - could effect ANS control of salivary glands
Radiotherapy
Diseases - Sjogrens syndrome

114
Q

What are the consequences of reduced salivary flow?

A 
Increased dental caries
Increased oral disease
Dysaesthesia (burning mouth)
Impaired oral function
Diminished taste perception
115
Q

How do you manage xerostomia?

A

Depends on cause
If functioning tissue gland present - stimulate salivary flow by chewing or drugs

If not - saliva substitutes either mucin based or cellulose based can be used

BAMS (14 decks)

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