Embryology

Question 1

At week 4 a membrane covering the primitive mouth separates the outer ectoderm layer of the developing face with the inner endoderm of the pharynx. Which best identifies this membrane?

Answer 1

oropharyngeal

Question 2

Around day 15-17 during gastrulation these cells differentiate into the 3 germ layers. What are the names of these cells?

Answer 2

epiblast cells

Question 3

During the development of the mandible, this cartilage forms a template for the bone which is made by intramembranous ossification. What is the name of the cartilage?

Answer 3

Meckel’s cartilage

Question 4

After coronal dentine formed and tooth eruption commences, when the cervical loop, outer enamel epithelium and inner enamel epithelium fuse to determine root shape. What does this then become known as?

Answer 4

Hertwig’s epithelial root sheath

Question 5

What is this tooth known as?

Answer 5

mesiodens

Question 6

What are these teeth known as?

What teeth does it most commonly affect?

Answer 6

supernumerary teeth

premolar region

Question 7

What stage of development are supernumerary teeth formed?

Answer 7

initiation stage

Question 8

What stage of development does macrodontia/microdontia occur?

Answer 8

bud stage

Question 9

At what stage does dens in dente develop?

Answer 9

cap stage

Question 10

At what stage does germination/fusion occur?

Answer 10

cap stage

Question 11

At what stage does tubercle occur?

Answer 11

cap stage

Question 12

At what stage does concrescence occur?

Answer 12

apposition/maturation stage

Question 13

What are the two main eruption models called?

Answer 13

continuous and limited eruption

Question 14

What are the 3 phases of eruption?

Answer 14

• pre-eruptive
• pre-functional
• functional

Question 15

What phase of eruption is being described?

- localised movements of the socket and movements due to growth

Answer 15

pre-eruptive phase of eruption

Question 16

What phase of eruption is described?

“major period of axial movement of tooth from developmental to functional position”

Answer 16

pre-functional phase of eruption

Question 17

What phase of eruption is being described?

“axial movements to accommodate for occlusal wear”

Answer 17

functional phase of eruption

Question 18

Crown completes … eruption (at approx. 3 years in adult)

Answer 18

before

Question 19

Root completes … eruption (at approx 3 years in adult)

Answer 19

after

Question 20

Teeth normally erupt when … of root length formed

Answer 20

2/3

Question 21

How prevalent is prenatal eruption?

Answer 21

1 in 2000 births

Question 22

Term used for when patients teeth are at rest and should not be meeting

Answer 22

vertical dimension at rest (RVD)

Question 23

Term used for when patients teeth are meeting

Answer 23

vertical dimension at occlusion (OVD)

Question 24

Term used for the space when patient is at RVD

Answer 24

free way space (FWS)

Question 25

What happens when there is an increase in free way space?

Answer 25

functional eruption

Question 26

What is being described?

• shedding of the deciduous teeth - root resorption
• bone remodelling
• PDL, cementum and dentine resorbed
• movement of the tooth germ
• root growth
• development of the cementum and PDL

Answer 26

some of the physical changes that happen during eruption

Question 27

What is being described?

• bone resorption
• sub epithelial connective tissue thins
• reduced enamel epithelium fuses with oral epithelium (compressed enamel organ)
• tooth erupts through epithelial cuff
• Nasmyths membrane, thin membrane of the reduced enamel epithelium that covers the tooth ones it has erupted (reminence of the compressed enamel organ)

Answer 27

some of the tissue changes during eruption

Question 28

Name 3 factors that eruption depends upon?

Answer 28

1. space in the eruption course created by the crown follicle
2. eruption pressure triggered by innervation in the apical root membrane
3. the ability of the PDL to adapt to eruptive movements

Question 29

What role does the periodontal ligament play in tooth eruption?

Answer 29

• myofibroblasts in PDL have contractile potential

- turnover of collagen in PDL recorded

Question 30

What is shown on the image? And how do they occur?

Answer 30

eruption cyst

where the tooth bud tries to push through the epithelial cuff and has not succeeded so therefore creates a cyst

Question 31

What can cause a disturbance in tooth formation?

Answer 31

• follicle - trauma
• virus
• failure to initiate resorption
• genetic conditions

Question 32

What systemic causes can then cause eruption deviations? (failure and delayed eruption)

Answer 32

• endocrine and various syndromes

Question 33

What factors can cause local eruption deviations such as failure, ectopic, impaction or transposition space? (5 points)

Answer 33

• tumours
• supernumerary teeth
• cysts
• primary tooth not shed
• ankylosis - a condition where a tooth fuses to the bone

Question 34

What is shown on the image? And how is it managed?

Answer 34

• dentigerous cyst - fluid filled cyst - an example of a local eruption deviation that can affect tooth erupting
• can be surgically removed or cut into and deflated

Question 35

What condition is shown on the image? And how is it caused?

Answer 35

• cherubism

- caused by multiple cysts inside the jaw

Question 36

What is shown on the image? And what symptoms could a patient have?

Answer 36

• complex odontoma (benign tumour) - can contain teeth in some cases
• can apply pressure to the inferior alveolar nerve and cause pt to have numbness

Question 37

What is shown on the image? And how can it be treated?

Answer 37

• mesiodens

- remove the supernumerary

Question 38

What is the name of the tooth on the image? And how is it caused?

Answer 38

• divergent root
• disturbance in the formation of Hertwigs root epithelial sheet
• trauma

Question 39

What is meant by the term Anodontia?

Answer 39

• missing teeth

Question 40

What is meant by the term Hypodontia?

Answer 40

• complete or partial missing teeth

Question 41

What is meant by the term Oligodontia?

Answer 41

• more than 6 teeth missing

Question 42

What are the 4 main factors that cause disturbances in tooth formation?

Answer 42

• hereditary
• endocrine dysfunction, systemic disease
• excess radiation
• disturbance during the initiation stage

Question 43

What are the most common groups of teeth that are more prone to being missing?

Answer 43

• upper incisors and laterals
• lower premolars
• wisdom teeth

Question 44

What are some conditions that cause missing teeth?

Answer 44

• cleft lip/palate
• ectodermal dysplasia
• down syndrome
• amelogenesis imperfecta

Question 45

What are some conditions that can cause multiple supernumerary teeth?

Answer 45

• Ehlers-danlos syndrome (also pulp stones and roots that are deformed)
• gardner syndrome (multiple polyps, autosomal dominant)
• cleidocranial dysostosis (poorly developed or no collarbones)

Question 46

What are some systemic conditions that can cause eruption disturbances?

Answer 46

• malnutrition
• hypothyroidism
• hypopituitarism
• hypoparathyroidism
• anaemia
• renal failure

Question 47

What is this a description of?

• in these bands, enamel prisms are arranged in layers of varying thickness at about right angles to each other
• strengthen the enamel and prevent cracks from propagating through the tooth

Answer 47

Hunter-Schreger bands

Question 48

What are the 3 periods of prenatal development and when do they occur?

Answer 48

• preimplantation period, first week
• embryonic period, second to eighth week
• fetal period, third to ninth month

Question 49

What happens during the preimplantation period of development?

Answer 49

Zygote - fertilised egg divides early on, then develops into blastocyst

• Zygote undergoes mitotic cleavage (cell division) in the first few days after it has been fertilised
• It then compacts and then will move down through the Fallopian tubes to the side of the uterus and become implanted

Question 50

What happens during the embryonic period of development?

Answer 50

Implantation of the blastocyst into uterus during 2nd week
Disc of the embryo starts to develop
Embryo starts to develop features of a human baby

Question 51

What happens during fetal period of development?

Answer 51

Embryo develops into foetus

Question 52

What is the name of this process?

Description - One cell group act on another, leads responding tissue to develop

Answer 52

Induction

Question 53

What is the name of this process?

Description - Controlled cellular growth and accumulation of by-products

Answer 53

Proliferation

Question 54

What is the name of this process? Description - Change in identical embryonic cells to become distinct structurally and functionally

Answer 54

Differentiation

Question 55

What is the name of this process? Description - Development of specific tissue structure or differing from due to embryonic cell migration or proliferation and inductive interactions

Answer 55

Morphogenesis

Question 56

What is the name of this process? Description - Attainment of adult function and size due to proliferation, differentiation and morphogenesis

Answer 56

Maturation

Question 57

What are the names of the three germ layers?

Answer 57

• Ectoderm (outer layer)
• Mesoderm (middle layer)
• Endoderm (inner layer)

Question 58

What germ layer do the following derive from? - Epithelial linings of the aero and digestive tracts, gut, liver, stomach and pancreas

Answer 58

Endoderm cells

Question 59

What germ layer do the following derive from? - Muscle and connective tissue, cartilage, blood, bone, serous membranes

Answer 59

Mesoderm cells

Question 60

What germ layer do the following derive from? - Skin and nerves, epidermis, nervous system, tooth enamel, neural crest cells

Answer 60

Ectoderm cells

Question 61

What germ layer do neural crest cells derive from?

Answer 61

Both ectoderm and mesoderm, migration happens from ectoderm cells to mesoderm cells

Question 62

What does the blastocyst contain that then becomes the foetus?

Answer 62

Inner cell mass

Question 63

What happens to the inner cell mass once the blastocyst has implanted into the uterus wall?

Answer 63

• Moves to one side and becomes classified as epiblast cells

Question 64

What are the names of the two types of cells that are formed within the blastocyst and migrate to opposite sides?

Answer 64

epiblast and hypoblast cells

Question 65

What is the term used for a disc with two sides?

Answer 65

bilaminar disc

Question 66

What does the yolk sack of the embryo become?

Answer 66

the supporting structure of the uterus

Question 67

A (embryo)

What structure is labelled A?

Answer 67

yolk sack

Question 68

B (embryo)

What type of cells are shown on the image labelled B?

Answer 68

hypoblast cells

Question 69

C (embryo)

What structure is shown on the image labelled C?

Answer 69

bilaminar disc

Question 70

D (embryo)

What type of cells are shown on the image labelled D?

Answer 70

epiblast cells

Question 71

What is the term used to describe this process ‘‘the purpose of … is to position the 3 germ layers endoderm, mesoderm and ectoderm which later develop into certain bodily systems’’ ?

Answer 71

gastrulation

Question 72

What part of the foetus develops at the primitive streak and the primitive node?

Answer 72

spinal cord

Question 73

When does gastrulation occur?

Answer 73

Day 15-17

Question 74

During gastrulation, we now have the distinction of the 3 germ layers and there is an invagination of the tissues at the … ?

Answer 74

primitive streak (midline)

Question 75

During gastrulation, epiblast cells turn into the … ?

Answer 75

ectoderm layer

Question 76

During gastrulation, there is an ingrowth of the germ layer in the middle which will become the future … ?

Answer 76

mesoderm layer

Question 77

During gastrulation, on the other side of the disc where the hypoblast cells will disappear, the … will emerge?

Answer 77

endoderm layer

Question 78

What is meant by the term ‘trilaminar embryo’ ?

Answer 78

there are 3 layers, endoderm, ectoderm and mesoderm

Question 79

What is the name of the process when the central nervous system is developed?

Answer 79

neurulation

Question 80

When does neurulation occur?

Answer 80

Day 18-28

Question 81

What is an example of a neural tube defect? (where it does not close all the way during neurulation)

Answer 81

spina bifida

Question 82

What supplement do pregnant women take to encourage closure of the neural tube during neurulation?

Answer 82

folic acid

Question 83

During neurulation, there is the disc of 3 layers, in the midline there is a joining of the cells that become known as the … ?

Answer 83

neural plate

Question 84

During neurulation, the process of the 3 layers folding in on themselves is called … ?

Answer 84

invagination

Question 85

During neurulation, neural plate cells become the … ?

Answer 85

neural groove (a groove down the midline of the disc)

Question 86

During neurulation, the neural groove comes together at the top and becomes the …

Answer 86

neural tube

Question 87

The neural tube is the future …

Answer 87

spinal cord

Question 88

After neurulation, when there has been closure of the groove and the neural tube is developed, some of the cells from the ectoderm layer start to migrate, these are called the … ?

Answer 88

neural crest cells

Question 89

After neurulation, the neural crest cells move into the tissues and become a tissue called … ?

Answer 89

ectomesenchyme

Question 90

In the head and neck, … contribute to the traditionally mesodermal tissues

Answer 90

neural crest cells

Question 91

The cranial end of the embryo indicates the region of the future … ?

Answer 91

brain

Question 92

The caudal end of the embryo indicates the region of the future … ?

Answer 92

spinal cord

Question 93

What is the name of the membrane that separates the 3 germ layers once the body has reached full growth as an adult?

Answer 93

basal membrane

Question 94

What are two examples of when the basal membrane is broken down and you have ectodermal tissues cross over?

Answer 94

• squamous cell carcinoma

- formation of enamel

Question 95

How far into development does the formation of the pharyngeal arches begin?

Answer 95

4 weeks

Question 96

During formation of the pharyngeal arches, sensory organs are described in the foetal stage as … ?

Answer 96

placodes

Question 97

The mandible is formed from the … pharyngeal arch?

Answer 97

first

Question 98

Just above the first pharyngeal arch, there is something called the maxillary prominence, which becomes the … ?

Answer 98

maxilla

Question 99

During formation of the pharyngeal arches, … come from the ectodermal area and migrate into the pharyngeal arches

Answer 99

neural crest cells

Question 100

What condition can a baby have if the maxilla does not fuse at the midline?

Answer 100

cleft palate

Question 101

During the contribution of the germ layers to the pharyngeal arches, there is an inside and an outside of the arches, the inside lining is … ?

Answer 101

endoderm

Question 102

During the contribution of the germ layers to the pharyngeal arches, there is an inside and an outside of the arches, the outside lining is … ?

Answer 102

ectoderm

Question 103

During the contribution of the germ layers to the pharyngeal arches, there is an inside and an outside of the arches, the middle lining is … ?

Answer 103

neural crest cells and mesoderm

Question 104

What are the 4 components of the pharyngeal arches?

Answer 104

1 - central cartilage rod (forms skeleton)
2 - muscular component
3 - vascular component (aortic arch artery)
4 - nervous component (cranial nerves)

Question 105

On the inside of the pharyngeal arches is the endoderm and on the outside is the ectoderm, normally these are separated by the tissues in the arch, but where they meet in between each arch, they come together, so the endodermal tissue will touch the ectodermal tissues. From the outside, we call this area a … ?

Answer 105

cleft

Question 106

On the inside of the pharyngeal arches is the endoderm and on the outside is the ectoderm, normally these are separated by the tissues in the arch, but where they meet in between each arch, they come together, so the endodermal tissue will touch the ectodermal tissues. From the inside, we call this area a … ?

Answer 106

pouch

Question 107

Where the pharyngeal arches meet, they form a membrane and those membranes end up being tissues that that make up the foetus. What pharyngeal arches do they derive from?

Answer 107

first and second

Question 108

What is the name of the early oral cavity?

Answer 108

the stomodeum

Question 109

At the early stage of development, the early oral cavity is separated from the amniotic fluid by a membrane and this is called the … which breaks down

Answer 109

oropharyngeal membrane

Question 110

What does the otic placode become in early development?

Answer 110

the ear

Question 111

What cranial nerve is associated with the 2nd pharyngeal arch?

Answer 111

facial

Question 112

What cranial nerve is associated with the 1st pharyngeal arch?

Answer 112

trigeminal

Question 113

What cranial nerve is associated with the 3rd pharyngeal arch?

Answer 113

glossopharyngeal

Question 114

What cranial nerve is associated with the 4th pharyngeal arch?

Answer 114

vagus

Question 115

What cells do the cranial nerves derive from?

Answer 115

neural crest cells and ectoderm cells

Question 116

What component of the oral cavity comes from more than one of the pharyngeal arches?

Answer 116

the tongue

Question 117

What are the stages of final position of the tongue?

Answer 117

• Tongue takes up the whole of the oral cavity
• Due to there being no nasal septum, there is an open space where the tongue will develop into
• Then the maxilla will develop, tongue will retract and sit into its final position

Question 118

What develops in the 1st membrane that separates the endoderm and ectoderm of the pharyngeal arches?

Answer 118

ear/eardrum

Question 119

What develops in the 2nd membrane that separates the endoderm and ectoderm of the pharyngeal arches?

Answer 119

palatine tonsil

Question 120

What develops in the 3rd membrane that separates the endoderm and ectoderm of the pharyngeal arches?

Answer 120

thymus and inferior parathyroids - before migrating to the area they will eventually end up

Question 121

What develops in the 4th membrane that separates the endoderm and ectoderm of the pharyngeal arches?

Answer 121

superior parathyroids

Question 122

What pharyngeal arch does the maxillary prominence derive from?

Answer 122

first

Question 123

The … in the pharyngeal arches are there for support and will disappear later on, only there as a scaffold

Answer 123

cartilage rods

Question 124

What is the name of the cartilage in the second pharyngeal arch?

Answer 124

Reicherts cartilage

Question 125

What is the name of the second pharyngeal arch?

Answer 125

hyoid

Question 126

What structures does the 1st pharyngeal arch form?

Answer 126

jaws

middle ear bones

Question 127

What structures does the second pharyngeal arch form?

Answer 127

facial muscles
middle ear bones
hyoid bone
tongue

Question 128

What structures does the 3rd pharyngeal arch form?

Answer 128

hyoid bone

tongue

Question 129

What structures does the 4th pharyngeal arch form?

Answer 129

laryngeal cartilages

tongue

Question 130

What are the name of the two parts that the neurocranium can be divided into?

Answer 130

calvaria

chondrocranium

Question 131

What is connective tissue?

Answer 131

• A group of tissues in the body that maintains the form of the body and its organs

Question 132

All dental tissues (except enamel) come from which germ layer?

Answer 132

mesoderm

Question 133

What germ layer does enamel come from?

Answer 133

ectoderm

Question 134

What are the 3 components of connective tissue?

Answer 134

1. Cells
2. Extracellular matrix
3. Ground substance - gel-like substance

Question 135

A lot of the cells that came up connective tissue will produce a protein that will come out of the cell membrane called … that will form a structure

Answer 135

extracellular matrix

Question 136

What happens to the cells in connective tissue once they have formed a tissue?

Answer 136

some will sit in the connective tissue and some will retract and disappear

Question 137

What is the role of connective tissue?

Answer 137

• scaffolding and support
• mobility and stretching
• homeostasis

Question 138

What is the term used for maintenance or keeping balance in the tissues?

Answer 138

homeostasis

Question 139

What is homeostasis?

Answer 139

• harbours stem cells for wound healing
• reservoirs of nutrients
• holds water

Question 140

When thinking about cells in connective tissue.

What are the cells called that secrete collagen for wound healing and maintain structure?

Answer 140

fibroblasts

Question 141

When thinking about cells in connective tissue.

What are the cells called that produces muscle tissue and fibres?

Answer 141

myofibroblasts

Question 142

When thinking about the cells in connective tissue.

What are the cells called that are fat producing cells?

Answer 142

lipoblasts

Question 143

When thinking about cells in connective tissue.

What are the cells called that are the cartilage producing cells?

Answer 143

chondroblasts

Question 144

When thinking about the cells in connective tissue.

What are the cells called that produces bone matrix?

Answer 144

osteoblasts

Question 145

When thinking about cells in connective tissue.

What are the cells called that create stem cells for specific tissues?

Answer 145

tissue specific stem cells

Question 146

When thinking about cells in connective tissue.

What are the cells called that produce something, secretes extra-cellular matrix?

Answer 146

a blast cell

Question 147

When thinking about cells in connective tissue.

What are the cells called that when it has produced something, the cell will become dormant?

Answer 147

a cyte cell

Question 148

When thinking about cells in connective tissue.

What are the cells called that break down something?

Answer 148

a clast cell

Question 149

What is a monocyte cell?

Answer 149

a white blood cell

Question 150

What are the 3 components of the extra-cellular matrix?

Answer 150

• fibrous structural proteins
• cell-surface proteins
• glycoproteins

Question 151

What is type 1 collagen produced by and where is it found?

Answer 151

Produced by fibroblasts, osteoblasts or odontoblasts

Found in scar tissue, bone, teeth, tendons and ligaments

Question 152

What does type 2 collagen make up?

Answer 152

50% hyaline cartilage

Question 153

What is type 3 collagen produced by and where is it found?

Answer 153

Produced by fibroblasts

Found in arteries and skin

Question 154

Where is type 4 collagen found?

Answer 154

basement membranes lining cavities and surfaces of organs

Question 155

What is the role of ground substance?

Answer 155

provide a route for communication and transport between tissues

Question 156

What are the names of the 2 mechanisms involved in bone differentiation and formation?

Answer 156

intramembranous ossification

endochondral ossification

Question 157

Most of the structures in the head are formed by … apart from the base of the skull

Answer 157

intramembranous ossification

Question 158

Most of the long bones in the body are formed by …

Answer 158

endochondral ossification

Question 159

What is the difference between intramembranous ossification and endochondral ossification?

Answer 159

intramembranous - doesn’t start with cartilage

endochondral - starts with hyaline cartilage

Question 160

… bone is the hard, outside of the bone

Answer 160

cortical

Question 161

… is the middle of a bone which is the spongy part

Answer 161

trabecular

Question 162

What is inside the inner most space of a bone?

Answer 162

stem cells

Question 163

How is bone formed?

Answer 163

• made from osteoblast cells that secrete osteoid matrix

- osteoid is mineralised to become bone, 60% organic

Question 164

What are the cellular components of bone and their roles in formation?

Answer 164

• osteoblasts - lay down the osteoid matrix
• osteocytes - osteoblasts in bone matrix lay dormant
• osteoclasts - break down some of the bone in order to keep it healthy

Question 165

How does alendronic acid work?

Answer 165

Stops the osteoclasts from breaking down bone, making the bones become denser and less likely to fracture in patients with brittle bones

Question 166

What are the risks of alendrotnic acid in dentistry?

Answer 166

Osteonecrosis of the jaw, after an XLA it can prevent the tissues from healing

Question 167

How is cartilage formed?

Answer 167

• Cartilage develops with chondroblast cells secreting cartilage matrix
• Once trapped within the matrix, chondroblasts differentiate into chondrocytes

Question 168

What are the two types of growth in which cartilage is formed and what are they?

Answer 168

• Appositional growth, layered growth

- Interstitial growth, deep in tissues

Question 169

What is perichondrium? And what does it provide for cartilage?

Answer 169

A membrane that lies outside of the bone

Cartilage relies on this as it is avascular

Question 170

What are the 3 main types of cartilage?

Answer 170

1. Hyaline cartilage
2. White fibrocartilage
3. Yellow elastic fibrocartilage

Question 171

What description of cartilage does this most describe? ‘most common, contains only collagen, weakest, all cartilage starts as this’

Answer 171

hyaline

Question 172

What description of cartilage does this most describe? ‘never found alone but with hyaline, TMJ, has no perichondrium, strong’

Answer 172

white fibrocartilage

Question 173

What description of cartilage does this most describe? ‘numerous elastic fibres as well as collagen, ear, larynx, epiglottis’

Answer 173

yellow elastic fibrocartilage

Question 174

All of the bones of the skull are formed from what process?

Answer 174

intramembranous ossification

Question 175

What part of the skull does the following description of the development best apply? ‘the bones are formed from growth centres from intramembranous ossification, condensation of the connective tissues then occurs, bone cells enter into these areas and start to lay down the bone matrix which then becomes calcified, this is then the centre where the bone expands towards the periphery, forming the joins of the suture as it matures’

Answer 175

the calvaria

Question 176

What are the following stages describing the cellular development of?

1. Mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification centre
2. Osteoblasts make an extracellular matrix ‘osteoid’
3. Osteoid matrix becomes mineralised, rudimentary bone tissue is formed

Answer 176

intramembranous ossification of the calvaria

Question 177

What is the periosteum?

Answer 177

fibrous membrane, providing protection and blood supply to bone

Question 178

When does the process of blood vessels being developed into the bone tissues begin?

Answer 178

when the bone matrix is being laid down

Question 179

What feature of the skull is being described? ‘contain actively dividing cells, allow the skull to grown to accommodate expanding brain, unique to the cranium’

Answer 179

sutures

Question 180

What part of the skull is the only part to be developed by endochondral ossification?

Answer 180

the base of the skull (chondrocranium)

Question 181

What week of foetal development do the endochondral ossification centres sit in order to make the structure for all the different foramina in the base of the skull?

Answer 181

5th and 8th week

Question 182

What are the 5 zones involved in the endochondral ossification formation of the chondrocranium?

Answer 182

1. Resting zone
2. Proliferating zone
3. Hypertrophic zone
4. Ossification or mineralisation zone
5. Primary spongiosa

Question 183

What is the name of the process described and what is being developed?

• All of the cells in the resting zone are cartilage cells, then something starts to happen in the tissues
• The cells then start to expand and become balloon-like in the hypertrophic zone
• Once this has occurred, the osteoblasts come into the tissues and the chondrocytes in the hypertrophic zone die off
• They are then replaced by the matrix that the osteoblasts laid down and this is how the bone formation/endochondral ossification takes place

Answer 183

endochondral ossification formation of the chondrocranium

Question 184

What part of the skull does this summary of development describe?

• plates of membranous bone
• separated by fontanelles and sutures
• formed by intramembranous ossification

Answer 184

calvaria

Question 185

What part of the skull does this summary of development describe?

• begins as small cartilage plates
• formed by endochondral ossification

Answer 185

chondrocranium

Question 186

What does the frontonasal process/prominence develop into?

Answer 186

forehead and front of the nose

Question 187

What does the lens placode later become?

Answer 187

future eye

Question 188

What does the nasal placode later become?

Answer 188

future nose

Question 189

What are being described? ‘On outer surface, sitting laterally on the face, specialised thickened ectoderm at location of special sense organs’

Answer 189

placodes

Question 190

Is the mandible formed by intramembranous or endochondral ossification?

Answer 190

intramembranous

Question 191

What is this the formation of? Fill in the blanks

• In the mandibular arch, there is Meckel’s cartilage, the cartilage sits there as a template to provide structure and rigidity to support the bone process of the …
• The bone tissues will form by intramembranous ossification for the majority of the …, so connective tissue cells are laid down which will become osteoblast cells and produce osteoid matrix.

Answer 191

mandible

Question 192

What is the following stages describing the end of development of?

1. When the bone is formed, you have growth of the bone towards the midline, this is where the chin is and where the growth finishes
2. Meckel’s cartilage disappears after bone formation

Answer 192

mandible

Question 193

Is the maxilla formed by intramembranous or endochondral ossification?

Answer 193

intramembranous

Question 194

When does foetal development of the maxilla begin?

Answer 194

4 weeks

Question 195

When does foetal development of the mandible begin?

Answer 195

4 weeks

Question 196

Stages of the … of development

• The maxilla grows towards the front, but also grows on the inside to form the palate in the oral cavity, at this stage there is no divide between the nasal and oral cavity.
• … moves forward towards the midline but doesn’t join up fully, they form a junction with the frontonasal process which goes down and fuses with the …

Answer 196

maxillary process (where the maxilla joins with the palate and the frontonasal process)

Question 197

What parts of the face come from the medial nasal process?

Answer 197

the midline and philtrum

Question 198

What part of the face comes from the lateral nasal process?

Answer 198

side of the nostril

Question 199

What part of the mouth comes from the frontonasal process?

Answer 199

where the maxillary incisors are

Question 200

Stages of the … of development

• Can be divided into different sections, where the nasal placodes, there is something called the medial nasal process and the lateral nasal process
• The lateral nasal process will join up to the maxillary process and also the medial nasal process and grow towards the midline and will become the tip of the nose

Answer 200

frontonasal process (where the frontonasal process joins up with the maxillary process)

Question 201

What is a consequence to the baby if there is failure of the fusion of the maxillary process with the medial nasal process?

Answer 201

unilateral or bilateral cleft lip

Question 202

What is the following a summary of the development of?

• follows Meckel’s cartilage
• formed mainly by intramembranous ossification
• woven bone turning to lamellar bone

Answer 202

mandible

Question 203

What is the following a summary of the development of?

• formed by intramembranous ossification
• midline palatine suture for lateral growth

Answer 203

maxilla

Question 204

What week of foetal development does palate formation begin?

Answer 204

5 weeks

Question 205

What week of foetal development is the palate fully completed?

Answer 205

12 weeks

Question 206

What are the 3 stages of palate formation?

Answer 206

• primary formation
• secondary formation
• final completion

Question 207

What part of the palate is meant by the following statement? ‘anterior segment that comes from the frontonasal process, grows down and joins up to the maxilla’

Answer 207

primary palate

Question 208

What part of the palate is meant by the following statement? ‘the back of the palate, the junction of the plates at the back’

Answer 208

secondary palate

Question 209

What part of the palate is meant by the following statement? ‘where the bone is fully developed, but also all the structures that sit behind the palate like the muscles, uvula etc.’

Answer 209

final palate

Question 210

What structure is being developed in this process?

- inter maxillary segment formation from fusion of the two medial nasal processes.

Answer 210

primary palate

Question 211

What structure is being developed in this process?
- maxillary processes form two separate palatal ‘shelves’, they fuse together and join in the midline at the front first to form the … and this is where you have the closing of the oral cavity from the nasal cavity’

Answer 211

secondary palate

Question 212

What 2 things have to happen during palate formation in order to have fusion at the midline?

Answer 212

1. tongue has to move down posteriorly of the oral cavity

2. two palatal process have to change direction and start growing towards midline

Question 213

Is the palate developed by endochondral ossification or intramembranous ossification?

Answer 213

intramembranous

Question 214

What part of the palate is not developed by intramembranous ossification?

Answer 214

posterior of the secondary palate (soft palate and uvula)

Question 215

Fill in the blanks
There is a condensation, almost like a horseshoe shape arch in the maxilla and the mandible ad this is called the …, from this you have dental buds where the stage of tooth development is initiated and this determines where the tooth is going to go which is genetically pre-programmed

Answer 215

dental lamina

Question 216

What stage of foetal development does the initiation stage of tooth development happen?

Answer 216

Week 6

Question 217

What is the term used to define the following?

‘cell changes, change function, change into different types of cells’

Answer 217

proliferation

Question 218

What is the term used to define the following? ‘describes the form of how the tooth is shaped’

Answer 218

morphogenesis

Question 219

What is the term used to describe the following? ‘tissues being laid down’

Answer 219

apposition

Question 220

What is the term used to describe the following? ‘fully mineralises and becomes functional tooth’

Answer 220

maturation

Question 221

What does the vestibular lamina become?

Answer 221

future sulcus

Question 222

What stage of tooth development is being described?

• 6th week in utero
• Ectodermal epithelium develops horseshoe shape thickening, which will becomes the dental lamina, next to deeper ectomesenchyme
• Neural tube marginal cells called neural crest cells migrate into the mesenchyme beneath the dental lamina, to form ectomesenchyme
• Ectoderm informs ectomesenchyme that a tooth will form, but the ectomesenchyme dictates which tooth and where

Answer 222

initiation stage

Question 223

Complex interaction between epithelial and mesenchymal tissues in tooth development.
Finish the sentence..
Between the formation of the enamel and dentine, growth factors and transcription factors signalling between the tissues, have to have … there first before the …

Answer 223

DENTINE there first before the ENAMEL

Question 224

What stage of tooth development is being described?

• 8th week in utero
• proliferation
• down growth of the dental lamina with 10 buds per arch for deciduous arch and lingually placed for permanent buds starting anteriorly of the mandible
• ectomesenchyme responds by proliferating
• leads to early enamel organ surrounding mesenchyme

Answer 224

bud stage

Question 225

What stage of foetal development does the bud stage of tooth development happen?

Answer 225

8th week

Question 226

What stage of foetal development does the cap stage of tooth development happen?

Answer 226

Week 9-10

Question 227

What stage of tooth development is being described?

• 9th to 10th week in utero
• further proliferation of epithelium, dictates shape of crown morphogenesis
• epithelium differentiates to form the enamel organ
• enamel organ forms a cap shape that surrounds the ectomesenchyme which is now called the dental papilla
• a surrounding mass of ectomesenchyme is named dental sac

Answer 227

cap stage

Question 228

What does the dental papilla develop into?

Answer 228

the pulp and dentine

Question 229

What does the dental sac develop into?

Answer 229

the cementum and periodontal ligament

Question 230

What is meant by the description?

- the cells that will produce the crown of the tooth

Answer 230

enamel organ

Question 231

In the cap stage of tooth development, what are the 3 elements that the tooth germ comprises of?

Answer 231

• enamel organ
• dental papilla
• dental sac

Question 232

What week of foetal development does the following happen?
- At this stage, there is a big change inside the mouth, at this point there is another dental lamina being laid down or there is another bud coming along and this is attached to some of the tooth germs in there and this is where the permanent teeth come from

Answer 232

Week 10 (cap stage)

Question 233

What stage of tooth development is being described?

• 11th-12th week in utero
• no mineralised tissues at this point
• enamel organ now comprised of: outer enamel epithelium, stellate reticulum, stratum intermedium, inner enamel epithelium

Dental papilla differentiates into:

• outer cells (future odontoblasts)
• central cells (future pulp)

Answer 233

bell stage

Question 234

What week of foetal development does the bell stage occur?

Answer 234

Week 11 and 12

Question 235

During the bell stage of foetal development, what 4 elements does the tooth germ become comprised of?

Answer 235

• outer enamel epithelium
• stellate reticulum
• stratum intermedium
• inner enamel epithelium

Question 236

In the appositional/secretory stage of tooth development, what do you need to have the presence of for the formation of enamel and dentine?

Answer 236

enamel organ and dentine matrix

Question 237

What stage of tooth development is being described?

• enamel, dentine and cementum laid down as a matrix
• preameloblasts and preodontoblasts formed
• preodontoblasts lay down predentine, basement membrane disintegrates forming EDJ and then become ameloblasts and secrete enamel matrix from Tomes process

Answer 237

appositional stage

Question 238

What are the key elements in the enamel matrix (organic)?

Answer 238

• amelogenin

- enamelin

Question 239

The tooth root, made of root dentin and root canals (where dental pulp lives), forms from a combination of three structures: …, … and another important group of cells known as …

Answer 239

1. dental papilla
2. dental sac
3. hertwigs epithelial root sheath

Question 240

What is the name given for the following?
They are discrete clusters of residual cells from Hertwig’s epithelial root sheath (HERS) that didn’t completely disappear

Answer 240

epithelial rests of Malssez

Question 241

Cementum provides attachment for the periodontal ligament via …

Answer 241

sharpey’s fibres

Question 242

What condition is shown on the image?

What teeth does it commonly affect?

Answer 242

microdontia (abnormally small teeth)

permanent maxillary lateral incisors (peg laterals) and third molars with partial microdontia (peg molar)

Question 243

What condition is shown on the image?

Answer 243

macrodontia (abnormally large teeth)

Question 244

What condition is shown on the image?

What teeth does it usually affect?

Answer 244

dens in dente

permanent upper lateral incisors

Question 245

What condition is shown on the image?

Answer 245

gemination/fusion

Question 246

What condition is shown on the image?

Answer 246

tubercle

Question 247

What condition is shown on the image?

Answer 247

concrescence

Question 248

What condition is shown on the image?

Answer 248

enamel dysplasia

Question 249

What condition is shown on the image?

Answer 249

amelogenesis imperfecta

Question 250

What condition is shown on the image?

Answer 250

dentinogenesis imperfecta

Question 251

What condition is shown on the image?

Answer 251

enamel pearl

Question 252

What dental tissue is being described?

• hard, non vascular and no sensation
• 96% mineralised, hydroxyapatite crystals, surrounded by amelogenin protein, enamelin and water
• cannot replace itself, but very hard to destroy
• rods are 5 microns diameter, getting wider nearer the surface

Answer 252

enamel

Question 253

What process is being described?
A histologic landmark identified on an ameloblast, cells involved in the production of tooth enamel. During the synthesis of enamel, the ameloblast moves away from the enamel, forming a projection surrounded by the developing enamel.

Answer 253

Tomes process

Question 254

The production of what dental tissue is being described?

• ameloblasts secrete enamel protein matrix, which mineralises due to addition of calcium phosphate crystals
• ameloblasts secrete through Tomes process
• crystals laid down in 2 different orientations (rod and interod)
• ameloblasts travels away from the EDJ, rods intertwine increasing the strength (hunter-schreger bands)

Answer 254

enamel production

Question 255

What dental tissue is being described?
- incompletely mineralised ribbon-like structures that run longitudinally to the tooth axis and extend from the dentinoenamel junction (DEJ)

Answer 255

enamel tufts

Question 256

… are fissure-like defects that extend along the longitudinal axis of the tooth down to the dentin layer (also get their name when enamel tufts are at full thickness)

Answer 256

enamel lamellae

Question 257

What element of enamel structure is being described?

• incremental growth lines, oblique from EDJ to surface, also in cross sections seen as rings
• possibly due to Tomes process restriction at end of secretory phase
• prominent … line is called neonatal line, but other variations may reflect illness, fever and may cause hypoplasia
• on surface they are represented as shallow waves called perikymata

Answer 257

striae of Retzius

Question 258

What dental tissue is being described?

• produced by odontoblasts
• by weight 70% inorganic (hydroxyapatite)
• softer than enamel but harder than bone
• 20% organic and 10% water
• elastic and flexible, underpins enamel and prevents it from fracturing, yellow giving teeth colour depending on enamel thickness

Answer 258

dentine

Question 259

The production of what dental tissue is being described?

• Formed by odontoblasts and composed of tubules with odontoblast process within
• Odontoblast end up within and form outermost layer
• Vital like bone and very sensitive
• Vascular connective tissue providing nourishment

Answer 259

pulp

Question 260

What microscopic dental structure is being described?

• dentinal tubules
• 2.5 micrometers wide at pulpal surface
• occlusally directed S shaped curves, as odontoblasts get crowded as they retreat towards pulp space, finer secondary curves

Answer 260

dentine structure

Question 261

What are the 4 types of dentine?

Answer 261

1. mantle
2. primary
3. secondary
4. tertiary

Question 262

What type of dentine is being described?
- First formed 30-150 micrometers of the primary dentine, first formed, less mineralised, loose collagen and trapped odontoblast terminal branches

Answer 262

mantle dentine

Question 263

What type of dentine is being described?

- Most of the tooth

Answer 263

primary dentine

Question 264

What type of dentine is being described?

- After root formation is completed, throughout life at pulpal edge, reducing pulp size

Answer 264

secondary dentine

Question 265

What type of dentine is being described?

• Induced by stimuli
• (reparative), responsive to events e.g. caries, fracture, cavity prep, irregular tubules, less permeable and protects the pulp, osteodentin (fast formed), type I and III collagen

Answer 265

tertiary dentine

Question 266

What are the 3 types of microscopic dentine?

Answer 266

1. peri/intratubular
2. intertubular
3. interglobular

Question 267

… contains dentinal tubules that have become completely obliterated by the deposition of peritubular dentin. This reaction by irritated odontoblasts forms a protective wall between themselves and noxious stimuli

Answer 267

sclerotic dentine

Question 268

What component of dentine is being described?
- an area of empty dentinal tubules beneath a carious lesion where the odontoblasts have died and not laid down sclerotic dentin

Answer 268

dead track

Question 269

What are the incremental growth lines of dentine called?

Answer 269

lines of Von Ebner

Question 270

Metabolic disturbances (birth, fever, infections) accentuate Von Ebner lines called…

Answer 270

contour line of Owen

Question 271

What tooth structure is being described?

• attached to the root dentine
• provides anchorage for collagen fibres of the PDL (sharpeys fibres)

Answer 271

cementum

Question 272

What are the two types of cementum?

Answer 272

• acellular: first formed over root dentine, covered by cellular cementum
• cellular: contains cementum forming cells

Question 273

What is being described?

- epithelial remnants of the Hertwig’s epithelial root sheath (HERS) that are involved in the formation of tooth roots

Answer 273

epithelial rests of Malassez

Question 274

What are the 4 functions of the periodontal ligament?

Answer 274

1. support
2. sensory
3. nutritive via blood supply
4. homeostasis

Question 275

What are the 3 elements of the periodontal ligament?

Answer 275

1. cells
2. fibres
3. ground substance

Question 276

What are the 5 elements of the pulp?

Answer 276

1. collagen
2. ground substance
3. blood vessels
4. rudimentary lymphatics
5. nerves

Question 277

What 2 types of nerves are in the pulp?

Answer 277

1. myelinated nerves - sensory, in dentinal tubules

2. unmyelinated nerves - are associated with the blood vessels

Question 278

What dental structure is being described?

• supports and protects the maxillary and mandibular teeth
• made up of both compact lamina dura and woven or spongy bone

Answer 278

alveolar bone

Question 279

What is being described?
thin membrane of the reduced enamel epithelium that covers the tooth once it has erupted (reminence of the compressed enamel organ)

Answer 279

nasmyths membrane