Bone Pathology Flashcards
What is Osteoporosis
Osteoporosis is a health condition that weakens bones, making them fragile and more likely to break. It develops slowly over several years and is often only diagnosed when a fall or sudden impact causes a bone to break (fracture).
- DIminisehd bone mass
- Disruption of microarchitecture
- Loss of trabeculae
- diminished bone strength
- Increased suscpetibility to insufficiency fractures
Embryonology of the parts of the bones
- Bone -develops from mesoderm (mesenchyme)
- Axial skeleton - from somites
- Appendicular skeleton from lateral mesoderm
- Cranial skeleton - directly from
- Mesenchyma - membranous bones
- Rest - throigj intermediate hyalien cartilage
What is osteogenesis and ossification
- Osteogenesis = whole process of development of an bone from mesenchyme
- Ossification = selective process of hardenign or radiological/histiological evidence of bone formation from membrane or crtilage
- Membranous ossification, Endochondral ossification, Osteogensis imperfecta.
What are the Classifications of bones:
- Anatomical - long, flat
- Structural:
- Macroscopic - cortical/comapct and cancellous/spongy
- Hisitiological - lamellar and woven
Bone histology:
Decsribe Woven Bone
- Not an orderly paralll array
- Intersecting, crisscross and woven arrangement
- Iregular thick and thin bundles
- Seen in foetus
- Recapitulated in fracture healing
Describe the Parts of a long bone
- Diaphysis - shaft (primary centre of ossification)
- Metaphysis - below the growht plate
- Epiphysis - upon/above the growht plate (secondary centre of ossification)
- Physis - growth (plate)
- Nutrient artery = through nutrient foramen - directed away from growing end- ‘to elbow i go, from the knee i flee- Milekrs position)
*
Where does provisional calcification start in the growth plate?
- Upper and lower hypertrophic zone
- Provisional calcification starts in latter which is storngest layer of growth plate compared to upper hyp zone which is the weakest and usually involved in growth plate injuries
- Zone of endochondral ossification - intense calcification and in continuity with metaphysis 4
What are the ones labelled G,H,O,R
G = Growth zone
H= hypertorphic zone
0 = ossification zone
R= Remodelling zone
What are labelled
Osteoid and osteoclasts
What is the sequence of longitudinal growth in long bone
- By provisional calcification of cartilage - endochondral ossification:
- Proliferation - increase in number by mitoses/cell division
- Hypertrophy - increase in size
- Maturation
- Degeneration
- Calcification
Describe Diametric Growth in long bones
- Miantained by periphysis
- Ring of La Croix- Surroundig epiphysis
- Zone of Ranvier - surroundign metaphysis.
What factors affect bone growth?
- Mechanical/Local - s-ace - epiphysiodesis and epiphyseal distarction
- Distractio osteosynthesis - Ilizarov
- Systemic- Endocrine, Paracrine, autocrine
- PTH-rP (parathyroid hormone related protein)
- Indian hedgehog Ihh proetin
Membranous ossification - Describe the main steps
- (Omit cartilage step)
- Primtiive emsenchyme -> osteoprogenitor cells 0> osteoblasts
- Lay down specialised collageb - osteoid
- Calcify
- Intramembranous ossification is the direct deposition of bone on thin layers ofconnective tissue and is characteristic of the bones on the top of the skull.
How do osteoclasts work with osteoblasts in th ebone remodelling cycle
- Osteoclasts - form cutting cone reusltign in resorption bays destroying bone
- Osteoblasts follow as closign cone laying new bone
- Junction visible as a purple blue cement line
- Constant renewal allows tensile strength to be retained
Pleuripotent mesenchymal stem cells: What can they differentiate into?
Cement lines in bone
The cement line, which is the interface between the ‘fibers’ (osteons) and extraosteonal bone matrix, may impart important mechanical properties to compact bone.
What are the 3 stages of fracture healing
- Inflammation (to) - haematoma + traumatic inflammation
- Repair (Within 2 weeks) - fibrous bridging if unopposed -> surfaces soft/provisional calludosteoid -> hard/definitive callus/spongy bone by mineralisation
- Remodelling - woven -> lamellated bone continues long after clinical healing
What does this image show
Provisional fracture callus, note zonation.
Arche sof bone - periosteal reaction form inner cambium layer - benign
