Histology of Bone, Cartilage, Joints and Synovium

Question 1

2 classifications of bone development

Answer 1

• Endochondral ossification
• Intramembranous ossification

Question 2

What bones develop by intramembranous ossification?

Answer 2

Flat bones of the skull, mandible and clavicle

Question 3

Formation of primary ossification centres in endochondral ossification

Answer 3

• 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

Question 4

Where do secondary ossification centres develop?

Answer 4

Epiphyses

Question 5

What is the epiphyseal growth plate?

Answer 5

• Layer of cartilage separating primary + secondary ossification centres
• Provides source of new cartilage in bone growth

Question 6

Development of a long bone by endochondral ossification

Answer 6

• 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

Question 7

Zones of the epiphyseal growth plate (epiphyseal side to diaphyseal side)

Answer 7

• Reserve cartilage
• Proliferation
• Hypertrophy
• Calcified cartilage
• Resorption

Question 8

How does a long bone grow in length but also retain its general shape?

Answer 8

• Resorption occurs in some places
• Deposition occurs in others

Question 9

What structural component differs between immature and mature bone?

Answer 9

Collagen fibre arrangement

Question 10

What is the Haversian system of osteons in mature bone?

Answer 10

• 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

Question 11

What arteries supply the ends of bones?

Answer 11

Metaphyseal + epiphyseal arteries

Question 12

How are bone marrow, spongy bone and deeper portion of compact bone supplied?

Answer 12

• Nutrient arteries pass obliquely through compact bone via nutrient foramina
• These divide into longitudinal branches in medullary cavity to proceed towards each end

Question 13

What is most compact bone nourished by?

Answer 13

Branches from periosteal arteries

Question 14

What allows pain to be felt in a bone fracture?

Answer 14

Sensory periosteal nerves in the periosteum that are especially sensitive to tearing or tension

Question 15

Components of a bone-remodelling unit

Answer 15

• Cutting cone
• Closing cone

Question 16

What form the cutting cone of a bone-remodelling unit and what do they do?

Answer 16

• Osteoclasts
• Bore/tunnel the resorption cavity through compact bone

Question 17

What form the closing cone of a bone-remodelling unit and what do they do?

Answer 17

• Osteoblasts
• Deposit osteoid on walls of canal in successive lamellae

Question 18

What happens during bone healing?

Answer 18

• 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

Question 19

2 main functional groups of joints

Answer 19

• Synovial
• Non-synovial

Question 20

How are articular surfaces maintained in apposition in a synovial joint?

Answer 20

Fibrous joint capsule + ligaments

Question 21

6 types of synovial joint

Answer 21

• Pivot
• Ball and socket
• Plane
• Hinge
• Saddle
• Condyloid

Question 22

3 types of non-synovial joint

Answer 22

• Syndesmosis
• Primary cartilaginous/synchondrosis
• Secondary cartilaginous/symphysis

Question 23

Structure of a syndesmosis

Answer 23

Dense fibrous tissue connects articulating surfaces

Question 24

Structure of a primary cartilaginous joint/synchondrosis

Answer 24

Hyaline cartilage connects articulating surfaces

Question 25

Structure of a secondary cartilaginous joint/symphysis

Answer 25

• Articulating surfaces covered with a layer hyaline cartilage
• Fibrocartilage plate directly connects articulating surfaces

Question 26

Layers of articular cartilage (and their chondrocyte arrangement)

Answer 26

• Superficial zone (elongated + flattened chondrocytes)
• Intermediate zone (round chondrocytes)
• Deep zone (chondrocytes arranged in short columns)
• Calcified zone (small chondrocytes surrounded by calcified matrix)

Question 27

Major constituents of synovial fluid

Answer 27

Hyaluronic acid + associated glycoproteins

Question 28

What does the fluid component of synovial fluid allow?

Answer 28

O2, CO2 + metabolite transfer between blood

Question 29

2 types of joints vertebrae articulate through

Answer 29

• Symphysial joints with intervertebral discs
• Facet synovial joints between with vertebral arch of other vertebrae

Question 30

Components of an intervertebral disc

Answer 30

• 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)

Question 31

How do tendons attach to bone?

Answer 31

• Collagen fibres of tendon + periosteum intermingle
• Fibres of tendon penetrate directly into bone (forms Sharpey fibres)