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Year 2 - Muscoloskeletal > MBD - Histopathology > Flashcards

MBD - Histopathology Flashcards

1
Q

Function of bone?

A

STRUCTURE
• gives structure & shape to body

MECHANICAL
• support & muscles attachment

PROTECTIVE
• vital organs & marrow

METABOLIC
• Ca2+ reserve (and other minerals)

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2
Q

Composition of bone?

A

INORGANIC - 75%
• calcium hydroxyapatite
• storehouse of 99% of body Ca2+
• 85% phosphorous, 65% Na, Mg

ORGANIC - 35%
• bone cells & protein matrix

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3
Q

Bone geography?

A

Epiphysis
• articular cartilage
• subchondral bone
• epiphyseal line

Metaphysis

Diaphysis (shaft)
• medulla
• cortex
• periosteum

ONENOTE FOR IMAGE!!

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4
Q

How are the different bone types classified?

A

ANATOMICAL BONES
• flat, long, short/cuboid, irregular, sesamoid

MACROSCOPIC STRUCTURE
• trabecular/cancellous/spongy
• cortical/compact

MICROSCOPIC STRUCTURE
• woven bone (immature)
• lamellar bone (mature)

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5
Q

Bone type classification - Macroscopic structure?

A 
CORTICAL
 • long bones
 • 80% of skeleton
 • appendicular
 • 80-90% calcified
 • mainly structural/mechanical/protective
CANCELLOUS
 • vertebrae/pelvis
 • 20% of skeleton
 • axial
 • 15-25% calcified
 • mainly metabolic
 • large SA
 • TRABECULAR bone is avascular
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6
Q

Cortical bone microanatomy?

A

Haversian canals = vertical in diagram

Volkmann’s canals = horizontal in diagram

Lacunae left by osteoclasts are called ‘Howship’s lacunae’

ONENOTE for diagram

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7
Q

What are the indications to carry out a bone biopsy?

A 
Evaluate bone pain
Investigate x-ray abnormalities e.g. brown lesions
Bone tumour diagnosis
Cause of unexplained infection
Evaluate medical therapy
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8
Q

Type of bone biopsies?

A

CLOSED
• Jamshidi needle, core biopsies - taken from ASIC (anterior superior iliac crest)

OPEN
• for sclerotic or inaccessible lesions

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9
Q

3 types of bone cells?

A

OSTEOBLASTS
• build bone & lay down osteoid
• surface osteoblasts go on to form osteoclasts

OSTEOCLASTS
• multinucleate
• resorb/remove bone

OSTEOCYTES
• mechansensory network embedded in mature bone
• osteoblast-like cells which sit in lacunae

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10
Q

What is RANK?

A

Receptor Activator for Nuclear factor Kappa B

  • found on osteoclast precursors in response to stimulation via. M-CSF
  • deals with osteoclast activation & differentiation
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11
Q

What is OPG?

A

Osteoprotegerin
• inhibits RANK/RANKL binding
SO
• inhibits osteoclastogenesis

It is a competitive inhibitor of RANK

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12
Q

Anatomical classification for bone types?

A

Long, flat, cuboid

  • Intramembranous ossification for flat bones
  • Endochondral ossification for long bones (NOT clavicle)
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13
Q

Functional classification for bone types?

A

TRABECULAR bone
• cancellous bone

OR

COMPACT bone
• cortical bone

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14
Q

Architectural classification for bone types?

A

WOVEN bone
• immature
• only physiological in fracture healing & at bast of teeth

LAMELLAR bone
• mature
• Trabecular lamellar bone can show ‘reversal lines
which indicate previous formation lines

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15
Q

Define MBD

A

Disorder of bone turnover due to imbalances of chemicals in the body

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16
Q

What is MBD?

A

Group of diseases that cause REDUCED bone mass & bone strength
• due to imbalance of various chemicals in the body (vits, hormones, minerals etc.)

Causes
 • altered bone cell activity
 • rate of mineralisation
OR
 • changes in bone structure
17
Q

What is reduced bone mass called?

A

Osteopenia

18
Q

Common MBDs?

A 
Osteoporosis
Osteromalacia/rickets
1o hyperparathyrpidism
Renal osteodystrohpy
Paget's disease
19
Q

3 main categories of MBD?

A

Endocrine abnormalities
e.g. VitD, PTH

Non-endocrine
• e.g. age-related osteoporosis

Disuse osteopenia
• e.g. astronauts in space

20
Q

Osteoporosis definition?

A

Defined as a BMD T-score of

21
Q

Osteomalacia definition?

A

Defective bone mineralisation of normally synthesised bone matrix
• rickets in children

Effectively 2 types:
• Deficiency of VitD
OR
• Deficiency of PO4

22
Q

Role of Vit D in osteomalacia?

A

VitD plays an imp. role in PTH secretion

• VitD deficiency stimulates release of PTH
AND
• subsequent bone resorption

23
Q

Most common cause of hypocalcaemia?

A

VitD deficiency

24
Q

How can low blood Ca2+ manifest?

A

Muscle spasms
Twitches
Tingling
Numbness

25
Q

Features of osteomalacia?

A

• Sequelae (condition which is the consequence of a previous disease or injury)

  • bone pain/tenderness
  • fractures e.g. horizontal fractures in Looser’s zone
  • Proximal myopathy
  • Bone deformity e.g. bowing in rickets
26
Q

Define hyperparathyroidism?

A

Excess PTH

27
Q

Features of hyperparathyroidism?

A
  • Increased Ca2+ & PO4 excretion in urine
  • Hypercalcaemia
  • Hypophosphatemia

• OSTEITIS FIBROSA CYSTICA (skeletal changes including brown tumours & kidney stones)

28
Q

Organs involved in hyperparathyroidism?

A 
Directly/indirectly affected by PTH & between them control Ca2+ metabolism
 • parathyroid glands
 • bones
 • kidneys
 • proximal SI
29
Q

1o & 2o hyperparathyroidism?

A

1o = parathyroid adenoma
• 85-90%
• results in chief cell hyperplasia

2o = chronic renal deficiency
• resulting in vitD deficiency

30
Q

Mnemonic to remember features of hyperparathyroidism?

A

SBAP

Stones
• Ca oxalate renal stones

Bones
• osteitis fibrosa cystica
• bone resorption

Abdominal groans
• acute pancreatitis

Psychic moans
• psychosis & depression

31
Q

Define renal osteodystrophy?

A

Comprises ALL the skeletal changes resulting from CHRONIC RENAL DISEASE

32
Q

What are the skeletal changes resulting from CRD as shown by renal osteodystrophy?

A
  • Increased bone resorption (osteitis fibrosa cystica)
  • Osteomalacia
  • Osteosclerosis
  • Growth retardation
  • Osteoporosis
33
Q

Features of renal osteodystrophy?

A

• PO4 retention/hyperpohsphataemia

• Hypocalcaemia
- because of low VitD

• 2o hyperparathyroidism
- low Ca2+ due to low VitD so reflex hyperparathyroidism

  • Metabolic acidosis
  • Aluminium deposition
34
Q

Define Paget’s disease?

A

Disorder of bone turnover

The formation breakdown leads to a mosaic effect in the bone

35
Q

How is Paget’s disease divided?

A

Divided into 3 stages:

  1. Osteolytic
  2. Osteolytic - osteosclerotic (bone formation)
  3. Quiescent osteosclerotic (quiescent stage)
36
Q

Who does Paget’s disease normally effect?

A
  • Onset >40year
  • Affects more males than females
  • Rare in asians & africans
  • Only affects one bone in 15% - mono-ostotic (most are poly-ostotic)
37
Q

Aetiology of Paget’s Disease?

A

Mainly unknown

Familial cases - autosomal mutation in SQSTM1 or RANK

Parvomyxovirus found in Pagetic bone

Overuse of previous bone injury

38
Q

Clinical symptoms of Paget’s Disease?

A

o Pain
o Micro fractures and bowing of tibia
o Nerve compression
o Skull changes may put the medulla at risk
o Deafness
o Haemodynamic changes and possible cardiac failure
o Hypercalcaemia
o Development of sarcoma (in area of involvement)

Year 2 - Muscoloskeletal (10 decks)

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