Histology of Bone, Cartilage, Joints and Synovium Flashcards
2 classifications of bone development
- Endochondral ossification
- Intramembranous ossification
What bones develop by intramembranous ossification?
Flat bones of the skull, mandible and clavicle
Formation of primary ossification centres in endochondral ossification
- Hyaline cartilage model formed
- Surrounding osteoprogenitor cells differentiate into bone-forming cells
- Bone deposited on cartilage surface
- Diaphysis later penetrated to form primary ossification centre
Where do secondary ossification centres develop?
Epiphyses
What is the epiphyseal growth plate?
- Layer of cartilage separating primary + secondary ossification centres
- Provides source of new cartilage in bone growth
Development of a long bone by endochondral ossification
- Cartilage model
- Periosteal bone collar forms around diaphysis
- Cartilaginous matrix in shaft begins to calcify
- Blood vessels + connective tissue erode + invade calcified tissue (creates primitive marrow) - remnant calcified cartilage spicules left at 2 ends of cavity
- Primary ossification centre develops, bone formed on spicules of calcified cartilage (bone at end of cavity constitutes metaphysis)
- Periosteal bone continues intramembranous ossification + blood vessels invade proximal epiphyseal cartilage
- Secondary ossification centre established in proximal epiphysis
- Similar formation of secondary centre at distal epiphysis
- Epiphyseal cartilage formed between each epiphysis + diaphysis (epiphyseal plate)
- As growth finishes, proximal epiphyseal cartilage disappears, metaphysis becomes continuous with epiphysis, epiphyseal plate become epiphyseal line
Zones of the epiphyseal growth plate (epiphyseal side to diaphyseal side)
- Reserve cartilage
- Proliferation
- Hypertrophy
- Calcified cartilage
- Resorption
How does a long bone grow in length but also retain its general shape?
- Resorption occurs in some places
- Deposition occurs in others
What structural component differs between immature and mature bone?
Collagen fibre arrangement
What is the Haversian system of osteons in mature bone?
- Concentric lamellar structures are organised around osteonal (Haversian) canals that contain the vascular + nerve supply of the osteon
- Perforating (Volkmann) canals perpendicularly connect osteonal canals to one another
What arteries supply the ends of bones?
Metaphyseal + epiphyseal arteries
How are bone marrow, spongy bone and deeper portion of compact bone supplied?
- Nutrient arteries pass obliquely through compact bone via nutrient foramina
- These divide into longitudinal branches in medullary cavity to proceed towards each end
What is most compact bone nourished by?
Branches from periosteal arteries
What allows pain to be felt in a bone fracture?
Sensory periosteal nerves in the periosteum that are especially sensitive to tearing or tension
Components of a bone-remodelling unit
- Cutting cone
- Closing cone
What form the cutting cone of a bone-remodelling unit and what do they do?
- Osteoclasts
- Bore/tunnel the resorption cavity through compact bone
What form the closing cone of a bone-remodelling unit and what do they do?
- Osteoblasts
- Deposit osteoid on walls of canal in successive lamellae
What happens during bone healing?
- Surrounding fibroblasts proliferate + secrete collagen to form a callus to hold bones together
- Callus calcification forms woven bone + callus hardens
- As woven bone is remodelled, lamellar bone is formed
2 main functional groups of joints
- Synovial
- Non-synovial
How are articular surfaces maintained in apposition in a synovial joint?
Fibrous joint capsule + ligaments
6 types of synovial joint
- Pivot
- Ball and socket
- Plane
- Hinge
- Saddle
- Condyloid
3 types of non-synovial joint
- Syndesmosis
- Primary cartilaginous/synchondrosis
- Secondary cartilaginous/symphysis
Structure of a syndesmosis
Dense fibrous tissue connects articulating surfaces
Structure of a primary cartilaginous joint/synchondrosis
Hyaline cartilage connects articulating surfaces
Structure of a secondary cartilaginous joint/symphysis
- Articulating surfaces covered with a layer hyaline cartilage
- Fibrocartilage plate directly connects articulating surfaces
Layers of articular cartilage (and their chondrocyte arrangement)
- Superficial zone (elongated + flattened chondrocytes)
- Intermediate zone (round chondrocytes)
- Deep zone (chondrocytes arranged in short columns)
- Calcified zone (small chondrocytes surrounded by calcified matrix)
Major constituents of synovial fluid
Hyaluronic acid + associated glycoproteins
What does the fluid component of synovial fluid allow?
O2, CO2 + metabolite transfer between blood
2 types of joints vertebrae articulate through
- Symphysial joints with intervertebral discs
- Facet synovial joints between with vertebral arch of other vertebrae
Components of an intervertebral disc
- Outer, compact region of dense fibrocollagenous tissue (AF)
- Thin layer of hyaline cartilage between AF + bone of vertebral body
- Central area of semi-fluid gelatinous matrix (NP)
How do tendons attach to bone?
- Collagen fibres of tendon + periosteum intermingle
- Fibres of tendon penetrate directly into bone (forms Sharpey fibres)
