Bone and cartilage

Question 1

what are the two types of macroscopic bone?

Answer 1

• cortical, compact bone - dense outer plate
• cancellous, spongy bone - internal trabecular scaffolding

Question 2

describe the alveolar bone?

Answer 2

• cortical bone nutrient canals containing blood vessels
• cortical bone lining tooth sockets is penetrated by bundles of collagen fibresof PDL (Sharpey’s fibres)

Question 3

what is the composition of bone?

3

Answer 3

60% inorganic - hydroxyapatitie
15% water
25% organic - collagen, glycoproteins, proteoglycans

Question 4

what is the extracellular matrix of bones composed of?

2

Answer 4

• ground substance - semi-fluid gel, long polysaccharide molecules, glycos-amino-glycans (GAGs)
• fibres - collagen, elastin, other non-collagenous proteins

Question 5

what are the two types of microscopic bone? what are the differences?

Answer 5

woven bone
* rapidly laid down
* irregular deposition of collagen
* present in fetus
* contains may osteocytes
lamellar bone
* laid down more slowly
* collagen fibres laid down in parallel
* normal form in adults
* contains fewer osteocytes

Question 6

what is the structure of compact bone?

Answer 6

laid down in concentric lamellae
form longitudinal columns
organised in Haversian systems around central Haversian canal
contain lateral Volkman’s canals
canals contain blood vessels

Question 7

what is shown in this picture?

Answer 7

Volkman’s canal linking two Haversian canals

Question 8

what is shown in this picture?

Answer 8

Haversian systems and canals

Question 9

what is shown in this picture?

Answer 9

ground section of a Haversian system (osteon)
small lacunae with radiating canaliculi = small canals
*some canaliculi link adjacent Haversian systems

Question 10

describe the structure of cancellous bone

Answer 10

network of thin trabeculae which consist of lamellae
osteocytes present
no obvious Haversian systems
bone is thin and nutrients can diffuse in
bone marrow present in spaces between trabeculae

Question 11

what are osteoblasts? what are they derived from? where are they found?

Answer 11

synthesise and secrete collagen fibres forming a matrix which is mineralised by calcium salts
lie on surface of bone
derived from mesenchymal stem cells

Question 12

what are osteocytes? where are they found?

Answer 12

osteoblasts that become trapped in mineralised bone and lie within spaces - lacunae
contact other osteocytes via cytoplasmic processes that run in canalicuni

Question 13

what are osteoclasts? what are they derived and related to? where are they found?

Answer 13

large multinucleate cells that resorb bone (acid phosphatases)
derived from haemopoietic stem cells and related to macrophages
lie in concavities in bone - Howship’s lacunae

Question 14

what is bone modelling? what is it controleld by? how is it regulated?

Answer 14

removal and replacement of bone tissue, without change in overall shape - resorption balanced by deposition (apposition)
controlled by osteoblasts
regulated by hormones and paracrines

Question 15

what is shown in this picture?

Answer 15

reversal line
* scalloped edge where bone resorption changes to bone deposition

Question 15

when does tooth movement occur? what does it require?

Answer 15

• during eruption
• post-eruptive (e.g. mesial drift)
• orthodontic procedures
  requires remodelling of adjacent soft and hard tissues

Question 16

describe the structure of cartilage

Answer 16

semi-rigid, unmineralised connective tissue
similar matrix to bone - ground substance and fibres

Question 17

where is hyaline cartilage found?

Answer 17

larynx, nasal septum, trachea, ends of ribs, articular surfaces, embryonic skeleton (precursor to bone)

Question 18

where is fibrocartilage found?

Answer 18

intervertebral discs, pubic symphysis

Question 19

where is elastic cartilage found?

Answer 19

external ear, epiglottis, eustacian tube

Question 20

how are cartilage cells formed? what do they contain?

Answer 20

formed by chondroblasts which get trapped in the matrix and become chrondrocytes
chondrocytes contain stores of lipid and glycogen
avascular - nutrients diffuses in

Question 21

what is endochondral ossification? what kind of bone does it occur with?

Answer 21

process that replaces cartilage with bone in long bones
cartilage precursor > cartilage proliferation > cartilage to bone

Question 22

what is intramembranous ossification? what kind of bone does it occur with?

Answer 22

process that creates bone tissue from mesenchymal tissue, a fibrous connective tissue in flat bones
no cartilage precursor, formed de novo

Question 23

what is achondroplasia?

Answer 23

genetic defect of cartilage growth
* endochondral bone growth is impaired but intramembranous bone growth is not as no cartilage precursor

Question 24

what happens to the jaw when someone loses all their teeth?

Answer 24

edentulous jaw - alveolar process is resorbed