Bone pathology Flashcards
Bone pathology, bone disease
What is the bone matrix composed of?
- Organic component: osteoid (90% type 1 collagen, 10% water, non-collagenous proteins, lipids, proteoglycas)
- Inorganic component of mineralised tissue (hydroxyapatite = hydroxylated calcium phosphate)
What is the consequence of the loss of inorganic matrix of the bone?
Flexible bones
What is the consequence of the loss of organic matrix of the bone?
Brittle bone
Describe the appearance and role of osteoclasts
Multinucleate, remove calcium from bone
Describe the histological appearance of osteocytes
Sit in lacunae, surrounded by matrix
Compare the ossification of long and flat bones
- Long: endochondral ossification at the metaphyseal growth plates (physes)
- Flat: intramembranous ossification, bone formed directly from he periosteum
Briefly describe the histological appearance of the physes of long bones
- Growth starts at hyaline cartilage (dark purple)
- Moves down into medullary cavity
- Then mineralises and ossifies, becomes pink
- Medullar cavity and spongy bone
What is the most common response of injured periosteum?
Formation of new bone e.g. around a fracture site
What is meant by brachygnathia?
Abnormally short jaw
What is meant by prognathia?
Abnormal projection of jaw
What is meant by kyphosis?
Dorsal curvature of the spinal column
What is meant by lordosis?
Ventral curvature of the spinal column
What is meant by scoliosis?
Lateral deviation of the spinal column
What is amelia?
Absence of limbs
What is hemimelia?
Absence of distal limb part
What is polydactyly and which animals are predisposed?
Presence of supranumerary digits, most common in cats, esp. Hemignway cats
What is adactyly?
Absence of a digit
What is syndactyly?
Fusion of digits
What causes chondrodysplasias?
Hereditary disorder of bone growth as a result of primary lesions in the growth cartilage
Which bones are affected by chondrodysplasias and why?
Long bones only, as only endochondral ossification is affected
Describe the appearance of an animal with chondrodysplasia
- Short legs and normal sized heads (dogs)
- Sheep usually normal length of legs but abnormal appearance of these (aka spider lamb syndrome)
- Also seen in cattle (bulldog cattle)
What causes osteopetrosis?
Defect in bone resorption by osteoclasts - plenty of osteoclasts but are not functioning correctly
Describe the consequences of osteopetrosis
- Bone mineral density increased, but bones are more fragile
- Not enough collagen
Which species are most commonly affected by osteopetrosis?
Cattle, sometimes horses
Give examples of congenital bone disorders
- Chondrodysplasia
- Osteopetrosis
- Osteogenesis imperfecta
- Congenital hyperostosis
- Osteochondromatosis
Give the main metabolic bone diseases
- Osteoporosis
- Rickets/osteomalacia
- Fibrous osteodystrophy
What are common causes of metabolic bone diseases?
Nutritional, toxic or endocrine
Describe the structure of bone affected by osteoporosis
Reduced bone mass, normal bone quality, well mineralised
List the main causes of osteoporosis
- Malnutrition Physical inactivity - Dietary calcium deficiency - Advanced age - Glucocorticoid excess (e.g. long term steroid administration) - Oestrogen or androgen deficiency
What are the consequences of osteoporosis?
- Brittle bones
- Fractures
Explain the difference between rickets and osteomalacia
- Failure ofmineralisation in growing skeleton (rickets) and adults (osteomalacia)
List the main causes of rickets/osteomalacia
- Calcium/vit D deficiencies
- Phosphorous deficiency
- Chronic renal disease (calcium phosphorous imbalance)
What are the consequences of rickets/osteomalacia?
- Bone deformities
- Thickening of growth plates
- Fractures
Describe the appearance of rachitic rosaries
- Occurs with rickets/osteomalacia
- Increased cartilage and fibrous connective tissue at costrochondral junctions
What is fibrous osteodystrophy?
- Similar to rickets but more severe, osteoclasts destroy bone
- Increased widespread osteoclastic resorption of bone and replacement by fibrous tissue
- Aka rubber jaw in dogs, bran disease in horses
List the causes of fibrous osteodystrophy
- Primary hyperparathyroidism
- Secondary hyperparathyroidism (renal/nutritional)
- Pseudohyperparahthyroidism (certain neoplasia)
- Lack of UV in reptiles
- Can also be seen as part of rickets
What are the consequences of fibrous osteodystrophy?
- Lameness
- Fractures
- Deformities
Compare the bone mineralisation in rickets/osteomalacia, osteoporosis and fibrous osteodystrophy
- Rickets/osteomalacia: reduced bone mineralisation (increased connective tissue)
- Osteoporosis: normal mineralisation (loss of spicules of bone, diaphysis gone)
- Fibrous osteodystrophy: fibrous replacement
List toxicities and nutritional imbalances that affect bone
- Hypervitaminosis D
- Vitamin C deficiency
- Vitamine A deficiency or toxicity
- Lead toxicity
- Fluoride toxicity