Bones Flashcards
What are the primary functions of bones?
- weight bearing/support
- protection
- mineral store
- blood formation (red bone marrow)
What are the different types of bones?
- flat bone (frontal)
- sutural bone
- short bone (carpal)
- irregular bone (vertebra)
- sesamoid bone (patella)
- long bone (femur)
What is the basic anatomy of bones?
- compact/cortical born or spongy/trabecular bone
- blood vessels
- medullary cavity
- bone marrow
- membranes
What are the two membranes present in bones?
Periosteum and endosteum
How is compact bone organised?
- circular structures (osteons/Haversian systems)
- central Haversian canals and horizontal perforating/Volkmann’s canals
- osteocytes and concentric rings of bone matrix (lamellae) around Haversian canal
What are the other names for spongy bone?
- cancellous
- trabecular
- diploe
What are the characteristics of spongy bone/structure?
- less dense than compact bone
- network of lamellated trabeculae filled with bone marrow
- no Haversian systems
- orientation of trabeculae reflect main directions of mechanical forces
What cells are included in bone composition?
- osteoclasts
- osteoblasts
- osteocytes
What is the composition of ECM in bones?
- roughly 45% hydroxyapatite crystals (complex form of calcium phosphate)
- roughly 35% collagen (type 1)
- roughly 20% water
What do minerals like hydroxyapatite do in bones?
- make bone stiff & able to support structures
- high strength under compression (like concrete)
What does collagen do in bones?
- gives bone some flexibility & reduces risk of fracture
- high strength under tension (like steel)
What are osteoclasts?
- large multinucleate cells derived from haematopoietic stem cells (like macrophages)
- have a “ruffled border” that releases acid to dissolve bone matrix
Where are osteoclasts found?
Bone surface
What is the function of osteoclasts?
Reabsorb bone matrix
What are osteoblasts?
- immature bone cells created from osteopregenitor cells in periosteum & endosteum
- become osteocytes once surrounded by matrix
What is the function of osteoblasts?
- produce bone matrix (unmineralised matrix = osteoid)
- initiate calcification
Where are osteocytes found?
Inside lacunae
What are osteocytes?
Mature bone cells
What is the function of osteocytes?
- not well understood
- may maintain bone matrix
- sense mechanical forces
What are canaliculi?
Connect lacunae to each other, which allows for communication between cells
What is osteoporosis?
Resorption > formation
What is Paget’s disease?
Increased resorption/formation
What is osteopetrosis?
Decreased resorption
What is bone mass controlled by?
Genes and environment
