(1) Anatomy and Histology of the Periodontium - Alveolar bone

Question 1

What is the alveolar bone?

Answer 1

The part of the jaw that supports and protects the teeth.

forms the tooth socket

Question 2

Is bone calcified?

Answer 2

YES

Question 3

What is the composition of bone?

Answer 3

Bone is composed of 60% inorganic component,

25% organic component and

15% water by weight.

Question 4

What is the main inorganic component of bone?

Answer 4

Calcium hydroxyapatite Ca10(PO4)6(OH)2

Question 5

What is the main organic component of bone?

Answer 5

Collagen (mainly type I) forms 90% of the extracellular matrix

Question 6

What is the most abundant type of collagen found in bone?

Answer 6

type I

Question 7

What form does Calcium hydroxyapatite adopt in bone?

Answer 7

needle-like crystallites or thin plates.

Question 8

What forms 90% of the ECM of bone?

Answer 8

collagen type I

Question 9

What are other organic component of bone other than collagen?

Answer 9

serum proteins, acidic glycoproteins and small proteoglycans.

Question 10

What substance is thought to be involved in mineralisation?

Answer 10

Osteonectin can bind to calcium and thus is thought to be involved in mineralisation.

Question 11

What are examples of glycoproteins found in bone organic matrix?

Answer 11

osteonectin, osteopontin, thrombospondin,
osteocalcin and fibronectin are also present.

Question 12

What is the role of proteoglycans in bone organic matrix?

Answer 12

Proteoglycans may regulate collagen fibril diameters and may
have a role in mineralisation.

Question 13

What are examples of proteoglycans found in the bone organic matrix?

Answer 13

chondroitin sulphate and heparan sulphate glycosaminoglycans

Question 14

What is the main form of chondroitin sulphate and heparan sulphate glycosaminoglycans (proteoglycans) in the bone organic matrix?

Answer 14

decorin and biglycan

Question 15

Osteocalcin is only synthesised by what (organic matrix)?

Answer 15

osteoblasts and odontoblasts.

Question 16

What is the role of locked in cytokines and growth factors in bone?

Answer 16

Exogenous proteins that circulate the blood and become locked in bone such as cytokines and growth factors have an important role in the life cycle of bone cells.

Question 17

What does BMP stand for?

Answer 17

Bone morphogenetic proteins (BMP)s

Question 18

How many proteins are in the BMP family?

Answer 18

16

Question 19

What family are BMPs a part of?

Answer 19

They are part of the transforming growth factor beta (TGF-β) family.

Question 20

What is the role of BMPs?

Answer 20

BMP(s) induce bone formation by influencing the movement, cell
division, and differentiation of stem and osteoproginator cells.

Question 21

Name the 5 bone cells

Answer 21

osteoblasts
osteocytes
osteoclasts
bone lining cells
osteoprogenitor cells

Question 22

What is the role of an osteoblast?

Answer 22

Osteoblasts secrete the organic extracellular matrix of new bone Osteoid which rapidly undergoes mineralisation to form bone.

Question 23

What is an osteocyte?

Answer 23

Osteoblasts become trapped in bone in lacunae as osteocytes.

Question 24

What is an osteoclast?

Answer 24

Osteoclasts are multinuclear cells involved in bone remodelling.

Question 25

What are bone lining cells?

Answer 25

flat cells line bone during periods of inactivity.

Question 26

What are osteoprogenitor cells?

Answer 26

Stem cells beneath the osteoblast layer.

Question 27

What are the 2 main forms of bone?

Answer 27

woven bone lamellar bone

Question 28

Describe the woven form of bone

Answer 28

immature bone, with random organisation of its collagen.

Question 29

Describe the lamellar bone?

Answer 29

Lamellar bone is composed of successive layers (lamellae). It may be formed as a solid mass (compact bone), or in an open sponge-like manner (cancellous bone).

Question 30

What are the 2 types of lamellar bone?

Answer 30

compact cencellous

Question 31

What type of bone is shown?

Answer 31

compact bone

Question 32

What is the structure of compact bone?

Answer 32

Compact bone is made of parallel bone columns which are disposed parallel to the long axis of long bones (in line of stress exerted on the bone).

Question 33

What is a bone layer called?

Answer 33

lamellae

Question 34

What is the structure of bone column in compact bone?

Answer 34

Columns are made of concentric bony layers (lamellae) arranged around a central channel with blood vessels, lymphatics and nerves (Haversian canals).

Question 35

Name structures A-C

Answer 35

Columns are made of concentric bony layers (lamellae) arranged around a central channel with blood vessels, lymphatics and nerves (Haversian canals).

Question 36

What do haversian canals with their lamalla form?

Answer 36

haversian systems (osteon).

Question 37

What are Volkmann’s canals?

Answer 37

channels that assist with blood and nerve supply from the periosteum to the Haversian canal

Question 38

How do neurovascular bundles interact with one another?

Answer 38

Volkmann’s canals that pierce the columns at right angle or obliquely to haversian canals.

Question 39

What do osteocytes in their lacunae interact with?

Answer 39

Osteocytes in their lacunae interact with each other and with the central canal via cytoplasmic extensions in canals called canaliculi.

Question 40

How do osteocytes interact with the central channel?

Answer 40

cytoplasmic extensions in canals called canaliculi.

Question 41

What is the outermost layer of compact bone called?

Answer 41

dense cortical bone.

Question 42

What does compact bone act as? What is the role of compact bone?

Answer 42

weight bearing pillars Compact bone is able to withstand high levels of mechanical stress.

Question 43

What is the innermost aspect of compact bone?

Answer 43

lamellae

Question 44

What does lamellae merge with ?

Answer 44

lamellae merge with trabeculae of cancellous (spongy bone).

Question 45

What is cancellous bone?

Answer 45

spongey bone

Question 46

Name structures 1 and 2 of spongy bone

Answer 46

Cancellous (spongy) bone is made of a network of bone trabeculae (2) separated by interconnected spaces containing bone marrow (1).

Question 47

What are the 2 components of spongy bone?

Answer 47

network of bone trabeculae separated by interconnected spaces containing bone marrow

Question 48

What is trabiculae?

Answer 48

Trabiculae are thin and composed of irregular bone lamellae.

Question 49

Does cancellous bone have haversian canals?

Answer 49

NO

Question 50

Where do osteocytes get their nutrition?

Answer 50

via canaliculi connecting them to blood sinusoids in the marrow.

Question 51

What is the role of spongy bone?

Answer 51

Spongy bone gives bone its flexibility due to the presence of marrow spaces.

Question 52

Where is trabeculae found?

Answer 52

Trabiculae are aligned along lines of stress so as to withstand forces applied to the bone while adding minimally to the mass.

Question 53

What separates sockets of alveolar bone?

Answer 53

interdental septa.

Question 54

What separates roots of alveolar bone?

Answer 54

interradicular septa.

Question 55

What is the fundus?

Answer 55

socket floor

Question 56

What are examples of exogenous proteins?

Answer 56

cytokines + growth factors

Question 57

What is a single unit of bone?

Answer 57

osteon

Question 58

What are the 2 forms of electron microscopy?

Answer 58

transmission scanning - surface (3D image of the surface)

Question 59

What do the small holes show in this image?

Answer 59

Where sharpeys's fibres into the bone inserted at right angles not fully mineralised bone

Question 60

What do the large holes in this image show?

Answer 60

lacunae where osteocytes can get trapped

Question 61

What is the difference between the above and below image?

Answer 61

above = fully anorganic electron microscopy (scanning) below = partially anorganic electron microscopy

Question 62

What does the bottom image show?

Answer 62

collagen fibrils parallel to the bone surface

Question 63

How would you describe Sharpey's collagen fibres?

Answer 63

extrinsic collagen fibres coming at right angles whereas intrinsic run parallel to the surface of bone

Question 64

What do A and B show in this electron microscopy image?

Answer 64

A = bone resorption ; howships lacunae B = longer snail track resorption lacunae

Question 65

What is bone called when there is no bone formation or resorption?

Answer 65

resting bone

Question 66

Name structures A-E

Answer 66

A = Alveolar bone B = Labial cortical plate C = body mandible D = lingual cortical plate E = cribriform plate the base of the tooth is the fundus

Question 67

In childhood, what is more predominant bone deposition or resorption?

Answer 67

deposition

Question 68

What is bone remodelling like in adult life?

Answer 68

equilibrium between bone deposition and resorption

Question 69

In old age, what is the bone remodelling like?

Answer 69

bone resorption exceeds deposition

Question 70

What does the bone on the right show?

Answer 70

osteoporosis bone mass is lost

Question 71

How are osteoblasts involved in bine remodelling?

Answer 71

Osteoblasts could stimulate the production of osteoclasts by the release of cytokines and growth factors, activate osteoclasts Osteoblasts could produce enzymes that degrade osteoid thus exposing bone for osteoclasts to work on.

Question 72

What is a reversal line?

Answer 72

Reversal lines (arrowed) marks the change in bone activity. between the newly formed bone and the old bone, represents the change in activity form bone resorption to bone formation.

Question 73

What do the black arrows show?

Answer 73

reversal lines could be evidence of a fracture

Question 74

Are bones constantly remodelled?

Answer 74

YES to adapt to pressure

Question 75

How often does spongy bone and compact bone remodel?

Answer 75

Spongy bone remodels 25% of its mass every year. Compact bone remodels 3% of its mass per year

Question 76

What is the bone called between 2 roots?

Answer 76

interseptal bone

Question 77

What are trans-septal sharpey's fibres? (or transseptal alveolar fibres)

Answer 77

enter the interseptal bone and exit through the other side and are continuous with the periodontal ligament on the other side of the interseptal bone

Question 78

Name A-C

Answer 78

Transalveolar fibres (A). B Periodontal Ligament C Dentine decalcified section