Sesh 7: Cartilage And Bone Flashcards
What is periosteum?
Dense, irregular connective tissue that covers the surface of bones.
What type of cartilage is ossified during endochondral ossification, to form most types of bone?
Hyaline cartilage.
Endochondral ossification increases bone ________.
Length.
What type of bone contains trabeculae?
Spongy/cancellous/trabecular bone.
What is intramembranous ossification?
Bone development directly from mesenchymal tissue, giving rise to mostly flat bones.
What is osteoid composed of?
Extracellular matrix + type I collagen
What are the spaces between trabeculae of spongy bone filled with?
Bone marrow
What runs through the centre of an osteon?
Haversian canal containing blood vessels, lymph and nerves.
What are Volkmann’s canals?
Run longitudinally along bone, not surrounded by concentric lamellae. Interconnect Haversian canals, so contain blood and lymph vessels, and nerves.
What are cannaliculi and what are their function?
Cytoplasmic processes of osteocytes that extend to other osteocytes via gap junctions to communicate and pass nutrients, and also connect with the Haversian canal.
How is the structure of spongy bone different to compact bone?
- No volkmann’s or haversian canals (get nutrients from bone marrow)
- Irregular lamellae
What is a cutting cone?
A bone remodelling unit that runs parallel to the orientation of osteons.
Why does bone density decrease with age?
Reduced osteoblast activity…less bone formed, but still being resorbed….imbalance in bone remodelling.
What % of bone is made of calcium hydroxyapatite crystals?
65%
What type of collagen makes up 23% of bone?
Type I
What are the 4 main stages of fracture repair?
- Haematoma formation
- Fibrocartilaginous callus formation
- Bony callus formation
- Bone remodelling
What is osteoporosis?
A metabolic bone disease in which bone resorption exceeds formation, leading to a reduction in bone mass and increased risk of fracture.
How does osteoporosis present?
Is mainly asymptomatic…may only present following a fall.
What’s the difference between type 1 and type 2 osteoporosis?
Type 1= post-menopausal women-reduced oestrogen so increased osteoclast
Type 2= elderly males+females, due to reduced osteoblast activity with age.
What effect does bedrest/bone immobilisation have on bone density?
Reduces bone density, as the reduced workload is sensed by osteocytes–> differentiate less into osteoblasts–>more bone resorption than formation.
What is osteoarthritis?
Disease due to wear and tear of joints causing bone-bone contact, and cartilage to wear away, leading to pain and reduced range of movement.
What is rheumatoid arthritis?
An autoimmune disease characterised by inflammation of synovial fluid, wearing away of cartilage and a reduced joint space/stretched joint capsule.
What type of cartilage are epiphyseal growth plates made of?
Hyaline.
Outline the steps in endochondral ossification.
- Collar of periosteal bone forms
- Nutrient artery penetrates, forming a primary ossification centre, and central cartilage calcifies
- Medulla becomes spongy bone and cartilage forms epiphyseal growth plates
- Secondary ossification centres from at epiphyses, and epiphyses ossify into spongy bone
- Columns on calcified cartilage extend from the growth plate
- In adult, epiphyseal growth plates replaced by bone
Calcified cartilage forms ________ onto which bone is laid down.
Spicules
Intramembranous contributes to ____________ growth of long bones.
Appositional (thickening)
Outline the stages of intramembranous ossification.
- MSCs form a small cluster-nidus- within the vascularised mesenchyme
- MSCs in nidus differentiate into osteoprogenitor cells
- Then differentiate into osteoblasts- lay down osteoid
- Osteoid mineralises to form immature bony spicules
- Spicules join to form trabeculae, which then merge to form woven bone
- Then replaced by lamellae of mature compact bone
What type of bone makes up 80% of the body’s skeletal mass?
Compact/periosteal/cortical bone
How can the lamellae of spongy bone be described?
Irregular
What is the name given to the area of the cutting cone in which osteoclasts release H+ and lysosymes?
The sealed zone.
