Metabolic bone disease – histopathology Flashcards
what is the function of bone?
STRUCTURE – give structure and shape to the body • MECHANICAL – sites for muscle attachment • PROTECTIVE – vital organs and bone marrow • METABOLIC – reserve of calcium and other minerals
what are the components of bone?
INORGANIC - 65%
– calcium hydroxyapatite (Ca10(PO4)6(OH)2)
– is storehouse for 99% of Calcium in the body
– 85% of the Phosphorus, 65% Sodium, Magnesium
• ORGANIC - 35%
– bone cells and protein matrix
what are the different types of bone?
Anatomical bones – Flat, long, short/cuboid, irregular, sesamoid • Macroscopic structure – trabecular/cancellous/spongy – cortical/compact • Microscopic structure – Woven bone (immature) – Lamellar bone (mature)
what are the two types of macroscopic bone?
CORTICAL • long bones • 80% of skeleton • appendicular • 80-90% calcified • mainly structural, mechanical, and protective
CANCELLOUS • vertebrae & pelvis • 20% of skeleton • axial • 15-25% calcified • mainly metabolic • large surface area
what is an osteon?
cylindrical structures in bone that contain a mineral matrix and living osteocytes connected by canaliculi, which transport blood. They are aligned parallel to the long axis of the bone. Each osteon consists of lamellae, which are layers of compact matrix that surround a central canal called the Haversian canal.
what are the different types of bone cell?
osteoCLAST- multinuclear, RESORB/REMOVE bone
osteoBLAST- produce osteoid to BUILD new bone
osteoCYTES- mechanosensory network embedded in mature bone
when might you carry out a bone biopsy?
Confirm the diagnosis of a bone disorder
• Find the cause of or evaluate ongoing bone pain or
tenderness
• Investigate an abnormality seen on X-ray
• For bone tumour diagnosis (benign vs malignant)
• To determine the cause of an unexplained infection
• To evaluate therapy performance
what are the two types of bone biopsy?
closed- needle
open- for sclerotic/ inaccessible lesions
what is metabolic bone disease?
• A group of diseases that cause reduced bone mass and
reduced bone strength
• Due to imbalance of various chemicals in the body
(vitamins, hormones, minerals, etc)
• Cause altered bone cell activity, rate of mineralisation, or
changes in bone structure
give some common metabolic bone diseases
- Osteoporosis
- Osteomalacia/Rickets
- Primary hyperparathyroidism
- Renal osteodystrophy
- Paget’s disease
what are the causes of primary and secondary osteoporosis?
1- age, post-menopause
2- drugs, systemic disease
what is osteomalacia? and what are the two types?
Defective mineralisation of normally synthesized bone
matrix
• Rickets in children. widening of growth plates and bowing of bone
• Effectively 2 types
– Deficiency of vitamin D
– Deficiency of PO4
also common to get looser’s zone horizontal fracture where the bone isnt strong enough to withstand the pressure
what are the effects of hyperparathyroidism on bone?
excess PTH causes increased bone resorption to increase Ca and decrease phosphate in blood.
hypercalcaemia, hypophosphatemia.
bone density is reduced
what are the primary and secondary causes of hyperparathyroidism
1º -
– parathyroid adenoma (85-90%)
– chief cell hyperplasia
2º -
– chronic renal deficiency
– vit D deficiency
what is the mnemonic for hyperparathyroidism symptoms
- Stones (Ca oxalate renal stones)
- Bones (osteitis fibrosa cystica, bone resorption)
- Abdominal groans (acute pancreatitis)
- Psychic moans (psychosis & depression)
