Clinically relevant bone biology

Question 1

Name the components of bone

Answer 1

• Connective tissue
• Cells
• Matrix

Question 2

Which 3 cells make up bone?

Answer 2

Osteoblasts
Osteocytes
Osteoclasts

Question 3

Which structures make up the bone matrix?

Answer 3

• Collagen

- Hydroxyapatite crystals: calcium and phosphorus

Question 4

What are the functions of bone?

Answer 4

• Skeletal support: strong, flexible, movement
• Protection
• Haematopoiesis (bone marrow)
• Regulation of mineral homeostasis
• Fat storage

Question 5

How do the cells making up bone develop?

Answer 5

• Osteogenic cell develops into an osteoblast

- Osteoblasts develop into osteoclasts

Question 6

What is the function of an:

• Osteoblast
• Osteocyte

Answer 6

• Osteoblast forms the bone matrix

- Osteocyte maintains bone tissues

Question 7

What are the 3 parts of the general bone structure?

Answer 7

Epiphysis
Metaphysis
Diaphysis

Question 8

Where is trabecular (cancellous) and woven bone found?

Answer 8

• Metaphysis
• Flat bones
• Cuboidal bones

Question 9

Describe the structure and functions of cortical bone

Answer 9

• Dense bone of diaphysis

- Supports weight, protects organs, provides levers for movement

Question 10

What is the function of trabecular (cancellous) and woven bone?

Answer 10

Dissipation of load

Question 11

Intramembranous ossification bone development is seen in which bones?

Answer 11

Flat bones e.g. skull, scapula

Question 12

Describe the process of Intramembranous ossification bone development

Answer 12

• Undifferentiated mesenchymal cells into osteoblasts
• Direct production of bone by osteoblasts
• Most do not have a marrow cavity

Question 13

Endochondral ossification bone development is seen in which bones?

Answer 13

Long bones

Question 14

Describe the main features of endochondral ossification

Answer 14

• Formation and replacement of a cartilage template by bone
• Increase bone length
• Physis (Growth plates): key structure required for longitudinal bone growth, made of 5 different zones

Question 15

What are the 3 stimulators of bone growth?

Answer 15

• Genetic template
• Hormones
• Load

Question 16

Describe and explain the process of bone modelling

Answer 16

• Ability of bone to change based on the strain put on it in the developing animal
• Osteoblasts form bone where there was none before
• Osteoclasts remove bone to alter the shape of the bone
• Work together

Question 17

What is bone remodelling?

Answer 17

Replacement of damaged bone

Question 18

Describe the features of bone remodelling

Answer 18

• Occurs within existing bone
• Occurs throughout life
• Rarely affects size and shape
• Seen in fracture repair
• Prevents accumulation of fatigue damage

Question 19

Which law is the primary regulator of bone remodelling?

Answer 19

Wolff’s law

Question 20

Describe Wolff’s law

Answer 20

Tension and compression cycles create a small electrical potential that stimulates bone deposition and increased density at points of stress

Question 21

What is the term given to decreased size and density of bone?

Answer 21

Osteoporosis

Question 22

What are the mechanical properties of bone dependant on?

Answer 22

• Size and shape of bone + mineralisation
• Magnitude of load
• Direction of load
• Rate of loading

Question 23

Name 5 forces that act on a bone

Answer 23

• Compression
• Tension
• Bending
• Torsion
• Shearing

Question 24

What are the 3 types of bone deformation caused by load?

Answer 24

• Elastic deformation

- Plastic deformation

Question 25

Describe elastic deformation

Answer 25

- With loading and unloading, the bone deforms but then returns to the original shape - Stimulates modelling

Question 26

Describe plastic deformation

Answer 26

With loading and unloading, the bone deforms but does not return to its original shape Stimulates remodelling

Question 27

What are 3 examples of plastic deformation

Answer 27

* Microcracks * Cyclic fatigue * Incomplete fractures

Question 28

What are the steps leading to complete failure of bone?

Answer 28

Elastic deformation -> as stress increases -> plastic deformation -> further stress -> failure = fracture

Question 29

What are the 2 causes of stress fratures?

Answer 29

Plastic deformation and repetitive loading

Question 30

How is the matrix affected by weakening of the normal bone structure?

Answer 30

- Metabolic effects | - Neoplastic effects

Question 31

What are the 2 causes of failure of normal bone?

Answer 31

- Single supra-physiological load e.g. External trauma i.e. Kick wound, Hit by car - Internal trauma e.g. foot planted and body twists

Question 32

Fracture of a weakened bone = ?

Answer 32

A stress fracture

Question 33

In which spp are stress fractures most commonly seen?

Answer 33

Race horses | Greyhounds

Question 34

Describe stress remodelling

Answer 34

- This is repetitive application of non-supra physiological load - When bone remodelling cannot keep up with bone damage

Question 35

Name some neoplasia's of bone

Answer 35

Osteosarcoma, Haemangiosarcoma, Multiple Myeloma, Chondrosarcoma

Question 36

Metabolic bone disease is caused by?

Answer 36

- Parathyroid hormone abnormality | - Vitamin D deficiency

Question 37

What is the function of vitamin D?

Answer 37

Amount of sunlight = Increases Ca from GIT

Question 38

What is the function of parathyroid hormone?

Answer 38

Removal of Ca from bone, decreases excretion from kidneys and increased Vit D formation

Question 39

What is the function of Calcitonin?

Answer 39

Removal of calcium from blood

Question 40

How does an increase in calcitonin lead to a decrease in Blood Ca levels?

Answer 40

- Increases calcium ion deposition in bones - Decreases Ca ion uptake in the GIT - Decreases Ca ion reabsorption from urine