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Body Logistics > Lecture 18: Bone Function And Repair > Flashcards

Lecture 18: Bone Function And Repair Flashcards

1
Q

What are the three main types of bone function?

A

Mechanical
Synthetic
Metabolic

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2
Q

What are the 3 mechanical functions of bone?

A

Protect tissues and organs
Provide framework for overall shape of body
Form basis of levers involved in movement

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3
Q

What is the synthetic function of bone?

A

Haemopoiesis - holds and protect bone marrow

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4
Q

What are the 3 metabolic functions of bone?

A

Mineral storage
Fat storage
Acid-base homeostasis

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5
Q

What are the 2 types of ossification?

A

Endochondral and intra-membranous ossification

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6
Q

What is endochondral ossification?

A

Formation of long bones from cartilage template

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7
Q

What is intra-membranous ossification?

A

Formation of bone from clusters of mesenchymal stem cells in the centre of bone

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8
Q

What is the key difference between endochondral and intra membranous ossification?

A

Endochondral needs cartilage template, intra-membranous ossification develops directly from mesenchymal tissue

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9
Q

What are the 6 stages of intramembranous ossification?

A
  1. Mesenchymal stem cells form tight cluster
  2. MSCs differentiate into osteoprogenitor cells and then into osteoblasts
  3. Osteoblasts lay down a osteoid
  4. Osteoid mineralized to form bone tissue spicules
  5. Spicules join to form trabeculae, which merge to form woven bone
  6. Traneculae replaced by the lamellae of mature compact bone
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10
Q

What are the 5 stages of cancellous bone conversion to cortical bone?

A
  1. MSC convert into osteoblast that line recently formed trabeculae
  2. Lay down mineralized osteoid
  3. Osteoblasts that are trapped become osteocytes
  4. Repeat steps 1 to 3 till done
  5. Central MSC converts into blood vessels, lymph vessels and nerve
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11
Q

What is immature bone?

A

Osteocytes in random arrangement

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12
Q

What is mature bone?

A

Osteocytes arranged in concentric lamellae of osteons

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13
Q

What is cancellous bone?

A

Network of fine body columns or plates to combine strength with lightness

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14
Q

What is compact bone?

A

Forms external surfaces of bones and comprises 80% of body’s skeletal mass

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15
Q

Why is bone so strong and able to resists fractures?

A

It has great tensile and compressive strength, a small degree of flexibility. Main force lines are through the cortical bone lamellae are thought to be able to slip, relative to each other to resist fracture

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16
Q

What are the 4 factors affecting bone stability?

A

Activity of osteocytes
Activity of osteoblasts
Activity of osteoclasts
Nutrition

17
Q

What are the 2 ways that the activity of osteocytes affect bone stability?

A

Osteocytes can act like osteoblasts and lay down scavenged osteoid into their lacunae (monitored by oestrogen or thyroid hormone)

Osteocytes can act like osteoclasts and degrade bone - osteocytic osteolysis (monitored by PTH)

18
Q

How does the activity of osteoblasts affect bone stability?

A

Bone deposition - stimulated by calcitonin, GH, oestrogen and testosterone, thyroid hormone, vitamin A

19
Q

How does activity of osteoclasts affect bone stability?

A

Bone resorption - releases calcium ions into the blood

Increased by PTH, decreased by calcitonin which blocks PTH receptor

20
Q

What are the 4 ways that nutrition affect bone stability?

A

D3 - produces calcitriol which enables calcium absorption
C - synthesis of collagen
K and B12 synthesis of bone proteins

21
Q

What are the 4 stages of fracture repair?

A
  1. Hematoma formation
  2. Fibrocartilaginous callus formation
  3. Bony callus formation
  4. Bone remodeling
22
Q

What are the 4 events that happen during haematoma formation?

A

Blood clot forms
bone cells at fracture edge die due to no blood supply
swelling and inflammation occurs as granulocytes enter
phagocytic cells and osteoclasts removes dead and damaged tissue

23
Q

What are the 3 events that happen during fibrocartilaginous callus formation?

A
  1. New blood vessels infiltrate the fracture hematoma
  2. Fibroblasts produce collagen fibres and differentiate into chondroblasts which puts down hyaline cartilage = fibrocartilaginous callus
  3. Osteoblasts from nearby periosteum invade the fracture site and begin bone reconstruction by forming spongy bone
24
Q

What are the 2 events during bony callus formation?

A

Endochondral ossification replaces all cartilage with cancellous bone

Intramembranous ossification produces new cancellous bone in any gaps

25
Q

What are the 2 events that happen during bone remodeling?

A

Hard callus is resorbed by osteoclasts and lamellar bone is deposited by osteoblasts

26
Q

What are 4 bone diseases?

A

Osteogenesis imperfecta
Rickets and osteomalacia
Osteoporosis
Achondroplasia

27
Q

What causes osteogenesis imperfecta?

A

Mutation in COL1A gene leads to incorrect production of collagen 1 fibers

28
Q

What are the 3 symptoms of osteogenesis imperfecta?

A
  1. Weak bones
  2. Short stature
  3. Blue sclera
29
Q

What causes rickets?

A

Vitamin D deficiency - poor calcium mobilization - ineffective mineralization leads to weakened bone development

30
Q

What are 4 symptoms of rickets?

A

Soft bones
Shortened height and stature
Painful to walk
Bowed legs

31
Q

What is the cause of osteomalacia?

A

Vitamin D deficiency - decreased mineralization = too much osteoid

32
Q

What are 4 causes of vitamin D deficiency?

A
  1. Kidney diseases
  2. No sunlight
  3. Surgery
  4. Drugs like phenytoin prevents vit D absorption
33
Q

What is type 1 primary osteoporosis?

A

Oestrogen normally regulates osteoclast numbers but after menopause there is loss of oestrogen so there’s an increase in osteoclast number = bone keeps being broken down

Affects post menopausal women

34
Q

What is type 2 primary osteoporosis?

A

Loss of osteoblast function due to loss of both oestrogen and androgen, bone not being deposited

Occurs in older men and women

35
Q

What are the 3 causes of secondary osteoporosis?

A

Result of drug therapy
Processes affecting bone remodeling
Metabolic bone diseases

36
Q

What are 3 modifiable risk factors of osteoporosis?

A
  1. Insufficient calcium intake: recommended 700mg/day for post menopausal women
  2. Exercise - immobilization leads to accelerated bone loss, physical activity is needed to maintain bone mass
  3. Cigarette smoking - in women, smoking correlated with incidence of osteoporosis
37
Q

What causes achondroplasia?

A

Inherited mutation in the FGF3 receptor gene which affects collagen formation from cartilage, affecting endochondral ossification but not intra-membranous ossification

38
Q

What are 3 symptoms of achondroplasia?

A

Short stature, but normal sized head and torso as it only affects long bones

Body Logistics (21 decks)

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