Metabolic Bone Disease – Histopathology Flashcards Preview

Y2 LCRS 2 - Musculoskeletal - Laz > Metabolic Bone Disease – Histopathology > Flashcards

Flashcards in Metabolic Bone Disease – Histopathology Deck (40)
Loading flashcards...
1

What are the three main functions of bones?

Mechanical – support and site for muscle attachment
Protective
Metabolic – reserve of calcium

2

What are the two main components of bone and what are their relative proportions?

Inorganic (65%) – calcium hydroxyapatite (store of 99% of the body’s calcium, 85% of the phosphorous and 65% of Na and Mg)
Organic (35%) – bone cells and protein matrix

3

Describe the classification of bone as cortical and cancellous.

Cortical
 Long bones
 80% of skeleton
 Appendicular skeleton
80-90% calcified
 Mainly mechanical and protective role
Cancellous
 Vertebrae and pelvis
 20% of skeleton
 Axial
15-25% calcified
 Mainly metabolic
 Large surface

4

What are the indications for bone biopsy?

Evaluate bone pain or tenderness
Investigate abnormality seen on X-ray
For bone tumour diagnosis
To determine the cause of unexplained infection
To evaluate therapy

5

What are the two types of bone biopsy?

Closed – needle – core biopsy with Jamshidi needle
Open – for sclerotic or inaccessible lesions

6

What are the three types of bone cell?

Osteoblast – build bone by laying down osteoid
Osteoclast – multinucleate cells of the macrophage family that resorb bone
Osteocyte – osteoblast like cells

7

Where are osteocytes found?

Lacunae

8

What cytokine is important for stimulating the differentiation of osteoclast precursors into pre-osteoclasts?

M-CSF (this is produced by osteoblasts)

9

Which cells produce RANKL and what is its effect?

Pre-osteoblasts
It stimulates the maturation of osteoclasts

10

What do mature osteoblasts produce that blocks the RANK/RANKL binding?

Osteoprotegrin

11

How are bones classified anatomically?

Flat
Long
Cuboid

12

What type of ossification leads to the formation of:
a. Long Bones
b. Flat Bones

a. Long bones
Endochondral ossification
b. Flat bones
Intramembranous ossification

13

How else can bone be classified?

Trabecular (cancellous) or compact (cortical)
Woven (immature) or lamellar (mature)

14

What is metabolic bone disease?

Disordered bone turnover due to imbalance of various chemicals in the body (vitamins, hormones, minerals etc.)
Overall effect is reduced bone mass (osteopaenia) often resulting in fractures from little or no trauma

15

What are the three main categories of metabolic bone disease?

Related to endocrine abnormality (e.g. Vit D and PTH)
Non-endocrine (e.g. age-related osteoporosis)
Disuse osteopaenia

16

Describe the staining of calcified and uncalcified bone.

Calcified – green
Uncalcified – orange

17

What are the primary causes of osteoporosis?

Age
Post-menopause

18

What are the secondary causes of osteoporosis?

Drugs
Systemic disease

19

Describe the histology of osteoporotic bone.

Weak trabecular bridging
Holes and cysts

20

What is osteomalacia and what can it be caused by?

Condition of defective bone mineralisation that can be caused by:
Vitamin D deficiency
Phosphate deficiency (usually related to chronic renal disease)

21

What are the metabolic and endocrine consequences of vitamin D deficiency?

Secondary hyperparathyroidism --> increased bone resorption
Hypocalcaemia – neuronal excitability causing muscle twitching, spasms, tingling and numbness

22

Describe the histology of osteomalacia.

No calcification of bone
More uncalcified osteoid
Bones are very bendy and cannot carry musculature very easily

23

What are the clinical consequences of osteomalacia?

Bone pain/tenderness
Fracture (horizontal fractures at Looser’s zone at the neck of the femur are commonly seen)
Proximal weakness
Bone deformity

24

What is used to investigate mineralisation?

Fluorescent tetracycline labelling

25

What are the consequences of hyperparathyroidism?

Hypercalcaemia (increased Ca2+ reabsorption)
Hypophosphataemia (increased phosphate excretion in the urine)
Osteitis fibrosa cystica (due to increased osteoclast activity)

26

List the four organs that are directly or indirectly affected by parathyroid hormone to control calcium metabolism.

Parathyroid glands
Bones
Kidneys
Proximal small intestine

27

State some causes of primary hyperparathyroidism.

Parathyroid adenoma
Chief cell hyperplasia

28

State some causes of secondary hyperparathyroidism.

Chronic renal insufficiency
Vitamin D deficiency

29

What are the symptoms of hyperparathyroidism?

Stones, Bones, Abdominal Groans and Psychic Moans
Stones – calcium oxalate renal stones
Bones – osteitis fibrosa cystica
Abdominal Groans – acute pancreatitis
Psychic Moans – psychosis and depression

30

What is the most important investigation for hyperparathyroidism and what will it show in someone with hyperparathyroidism?

X-ray of the hand
Subperiosteal bone erosions
Brown cell tumours – small areas of resorption in the long bones of the fingers that are filled with osteoclasts