Bones Flashcards
What is the structure and function of the skeletal system?
It includes bones joints cartilage ligaments and other connective tissues
Function- supports against gravity, leverage for muscles action, protection, storage, blood cell production
What are the classifications of bones?
Flat e.g. cranium with an internal and external table with a diploe between for protection
Long e.g. femur, movement
Short e.g. carpal bones for small movements
Irregular e.g. vertebrae
Sutural e.g. between the skull bones
Sesamoid e.g. develop in tendons
What is the structure of a long bone?
Shaft - diaphysis- compact dense bone surrounds the medullary cavity
Ends - epiphyses- compact layers but trabecular (spongy) bone - transfer forces in multiple directions
Articular cartilage - smooth cover of a bone to form a joint
What is the structure of bone tissue?
Ground substance- 2/3 of bone matrix, minerals - crystals of hydroxyapatite (hard but brittle)
Protein - 1/3 of bone matrix - type 1 collagen fibres - more resilient so can withstand impacts
Bone cells- 2% of mass- mesenchymal stem cells - form osteoblasts, osteocytes and osteoclasts
What is an osteoblast?
On the surface, produce protein which is mineralised to form new bone
What is an osteocyte?
Sit inside the bone - these are mature bone cells - have canaliculi which allow communication throughout the bone
What is an osteoclasts?
Multinucleated cell that secretes acids and enzymes to dissolve bone
What is the microscopic structure of compact bone?
osteons- basic functional unit of compact bone - strong in the long axis
Central canal - tunnel for blood vessels
Lamallae - concentric layers of matrix
Lacunae- contains cells- osteocytes
How is the structure of an osteon important?
Collagen fibres in opposite directions to increase strength
What is the structure of spongy bones?
No osteons
Trabeculae- arches, rods, strong in many directions, lined according to habitual loading patterns
Red marrow - between trabeculae, form red blood cells, nutrients to osteocytes
Yellow bone marrow - medullary cavity, stores fat
What is the periosteum?
Membrane outside bone
Outer fibrous layer with collagen
Inner layer - cells
Contains lymphatic vessels and nerves
What is the endosteum?
Membrane layer of cells lining bone medullary cavity, central canals and trabecular
What are the methods of bone formation and growth?
Intramembraneous ossification
Endochondral ossification
Appositional bone growth
What is intramembraneous ossification?
Formation of flat bones inside
Mesenchymal stem cells differentiated into osteoblasts, ossification forms spicules of bone
Trabecular bone formed
Remodeled into compact bone
What is endochondral ossification?
Bones form in cartilage
1. Chondrocytes within calcifying matrix enlarge then die
2. Osteoblasts cover the shaft in a thin layer of bone
3. Blood vessels and osteoblasts penetrate to form a primary ossification centre in the diaphysis
4. Centre enlarges
5. Secondary ossification centre form at epiphyses
