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**Oral Biology > Enamel 1 > Flashcards

Enamel 1 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q
  1. Is enamel Acellular or cellular?
  2. Is it Vital or non-vital?
  3. is it vascular or non-vascular?
A
  1. Acellular
  2. Non-vital
  3. Non-Vascular
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2
Q

What is the origin of enamel?

A

Ectoderm

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3
Q

Enamel is the Hardest (most mineralized) tissue in the body T/F

A

True

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4
Q

Enamel is brittle T/F

A

True

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5
Q

What makes enamel dynamic?

A

It can be demineralized and remineralized

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6
Q

Where is enamel thickest?

A

At the crown, around 2.5mm

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7
Q

What is the primary component of enamel?

A

Hydroxyapatatite crystals

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8
Q

What is the purpose of the protein component of enamel?

A

Organization of crystals

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9
Q

How much of the enamel is organic material?

A

1%, distributed between the HA crystals

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10
Q

T/F Enamel contains collagen within the organic component

A

FALSE. No collagen

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11
Q

Where would you find major enamel proteins?

A

In the organic component

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12
Q

What are the major enamel proteins?

A
  1. Amelogenins
  2. Ameloblastins
  3. Enamelin
  4. Tuftelin
  5. Others also exist
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13
Q

T/F some enamel proteins are present only in developing enamel

A

TRUE

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14
Q

How much of enamel is water?

A

2-3%

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15
Q

What are the 4 mineralized tissues in the body?

A
  1. Bone
  2. Dentin
  3. Cementum
  4. Enamel
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16
Q

What is main purpose of the tooth?

A

survive repeated cyclical loading

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17
Q

How are enamel crystals arranged?

A

Closely packed, long, ribbon like

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18
Q

Many Crystals packaged together form both the ______ and ______

A
  1. Enamel rods

2. Interrod enamel

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19
Q

While enamel crystals are called hydrdoxyapatite, lots of enamel crystals are actually ________

A

Carbonatoapatite

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20
Q

How is carbonatoapatite different from hydroxyapatite?

A

CO3(2-) can substitute for PO4(3-), usually, but can also substitute for OH- sometimes

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21
Q

T/F enamel grows outwards, dentin is forming inwards

A

TRUE

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22
Q

Is the composition of enamel measure by weight or by volume

A

Weight

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23
Q

Hydroxyapatite can incorporate Carbonate, Magnesium, fluoride, and other ions into its structure T/F

A

TRUE

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24
Q

Where are carbonate and magnesium usually incorporated?

A

Inner enamel

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25
Q

Where is fluoride usually incorporated into enamel?

A

Outer enamel

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26
Q

T/F Outer enamel is more resilient in the face of an acid attack

A

TRUE

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27
Q

Each enamel crystal is what shape?

A

Hexagonal, reflective of the individual HA unit cell

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28
Q

What are the mature dimensions of enamel crystals?

A

Width: 60-70 nm
Thickness: 25-30 nm

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29
Q

How long is an enamel crystal?

A

Very long (in the mm range), it could run the entire length of the enamel layer

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30
Q

What happens to hexagonal symmetry as the crystals mature?

A

It increases, but fully mature crystals lose their shape somewhat

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31
Q

Enamel rods generally run perpendicular to what?

A

DEJ (Pulp)

32
Q

What is an enamel rod?

A

Cylindrical accumulation of enamel crystals, lined up along the long axis of the rod

33
Q

T/F Rods are straight

A

FALSE

**Rods are not completely straight, but curve somewhat as they progress towards the surface

34
Q

Often rods are called _______

A

Prisms

**Technically they are not prisms because they are not that regular in terms of geometry

35
Q

What is a prism?

A

Polyhedron with 2 polygonal bases

36
Q

Rods are organized into ____ which run in alternating directions

A

Rows

37
Q

How many ameloblasts are associated with a rod?

A

One ameloblast for One rod

38
Q

T/F Orientation of enamel rods is best seen with Light microscopy

A

FALSE, Impossible to tell from light microscopy. Rods throw off light in all directions

39
Q

What is the Rod Sheath?

A

A relatively protein rich area of enamel that surrounds the rods

40
Q

The rod sheath runs about ___ of the way around each rod

A

3/4

41
Q

For the most part, rod sheaths separate ___ and ______ enamel

A
  1. Rod

2. Interrod

42
Q

What happens in the areas of the Rod that are not surrounded by a rod sheath?

A

The enamel crystals are continuous with interrod enamel, linking the two together

43
Q

Where is the crystal orientation in the rod not parallel to the long axis of the rods?

A

In the gap areas where they become continuous with interrod enamel

44
Q

What are the rod sheath proteins?

A
  1. Ameloblastins

2. Amelogenins

45
Q

Rod sheaths are much more prominent in ______ _______

A

Higher mammals (not so much in rodents)

46
Q

What is interrod enamel?

A

Same basic compositions as rods, simply different enamel crystal orientation

47
Q

What doe interrod enamel do?

A

Fill the gaps between rods

48
Q

Where is Caries though to penetrate?

A

Through the higher protein rod sheath areas (between rod and interrod enamel)

49
Q

An enamel rod head is _________ to surface of enamel

A

Perpendicular

50
Q

What is the composition of enamel as the ameloblasts are activated and enamel begins to be deposed?

A

-Only around 30% mineralized, with much larger organic component

51
Q

As enamel matures, what happens to the organic component of enamel?

A

It is reduced and mineralization of enamel increases

52
Q

What are the 3 general phases of Ameloblast maturation?

A
  1. Pre-secretory
  2. Secretory
  3. Maturation
53
Q

What is the pre-secretory phase?

A

Cells mature from pre-ameloblasts to ameloblasts

54
Q

What happens in secretory phase?

A

Deposition of enamel

55
Q

What is maturation phase of Ameloblasts?

A

Reduction of organic matrix, increase mineralization via ion transport

56
Q

How do Ameloblasts deposit organic matrix?

A

Via secretory vesicles which exit the cell apically

57
Q

Initially in the deposition of enamel, what happens to the basal lamina that separates the pre-dentin and ameloblasts?

A

It is penetrated by cell projections and broken down

58
Q

Enamel is laid down directly in appostion to what?

A

Pre-dentin/mantle (first) dentin

59
Q

What is Tomes’ process?

A
  • Forms during the deposition of enamel

- Projects into the developing enamel and is the site of much secretory activity

60
Q

What is holding ameloblasts together?

A

Junctional complexes (terminal bars)

61
Q

T/F Enamel has a rod arrangment even as soon as it is initially placed in appostion to dentin

A

FALSE, Initial enamel in apposition to dentin does not have a rod arrangement, it is uniform

62
Q

What does Tomes’ process form?

A

Effectively it forms the Enamel rod structure

63
Q

What are the distal and proximal orientations of Tomes’ process referring to?

A

Distal: Towards the forming enamel

Proximal: Towards the stratum intermedium

64
Q

Secretion from different parts of Tomes’ process forms what?

A

Rods, interrod enamel

65
Q

Inner enamel epithelium in tooth development become what?

A

Ameloblasts

66
Q

Trigger for ameloblasts to make proteins for enamel is what?

A

Formation of first pre-dentin

67
Q

What do ameloblasts do when enamel has been laid down?

A

The return to being a squat cell, much like a pre-ameloblast

68
Q

Prior to eruption what happens to enamel?

A

It hardens and becomes highly mineralized through the removal of water, organic material and increased HA crystal diameter

69
Q

How long does enamel maturation take?

A

Relatively slow: up to 5 years for some permanent teeth

70
Q

How much of amelognesis is maturation?

A

roughly 2/3

71
Q

What is modulation?

A

Process by which water and proteins are removed. Fluctuations in teh distal membrane of ameloblast layers ‘ruffing’ and ‘smoothing’

72
Q

How do ruffles cells come to be?

A
  • Infiltration and incorporation of calcium ions into crystals occurs during ‘ruffling’
  • Lowered pH perhaps favors mineralization
  • Secretion of proteolytic enzymes
73
Q

What are smooth cells?

A

Allow diffusion out of protein fragments out of enamel, which leak in between cells and laterally defuse through cell layer

74
Q

What happens to the enamel organ after after enamel maturation?

A

The remains of the enamel orgain are attached to the tooth until eruption at which point they fuse with the oral epithelium, forming a covering over the tooth

75
Q

What is the primary enamel cuticle?

A

A mineralized coating which is the last secretory product of the ameloblasts (Perhaps the basal lamina)

76
Q

What is the secondary enamel cuticle?

A
  • Also called ‘Dental Cuticle’
  • Formed from the remains of the reduced enamel epithelium merged with the oral epithelium and is removed due to mechanical forces and what not
77
Q

What does Nasmyth’s membrane refer to?

A

The primary and secondary enamel cuticle together

**Oral Biology (10 decks)

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