Bone and cartilage biology Flashcards
What makes up the extracellular matrix?
Organic (40%) = collagen, proteoglycans, non-collagenous proteins
Inorganic = calcium hydroxyapatite cyrstals
Collagen in bones
Mainly type 1
Diseases affecting the collagen = scurvy (vit c deficiency) and Osteogenesis imperfecta (DNA mutation in coding for type 1)
Proteoglycans in bone are?
Small and non-aggregating
What is the function of non-collagenous proteins in bone?
Control bone growth
What does calcium hydroxyapatite cyrstals do?
Gives mechanical strength and hardness to bones.
Osteoid stage of bone matrix development.
Stage 1 of matrix development
Collagen meshwork without mineralisation
Organic compounds only are secreted by the osteoblasts
Rickets and Oestomalacia causes the bone to stay at this osteoid stage
Woven bone stage of bone matrix development
Bone produced in a hurry
Randomly organised collagen fibres
crystals lie outside of the collagen fibres
secreted by osteoblasts in a hurry e.g. new bone formation (children) and repair
Mechanically weak and replaced by lamellae bone over time
Lamellar bone stage of bone matrix development
End stage, well organised and strong
Crystals lie within the fibres
Collagen is organised into lamellae, concentric circular layers in Haversian system
Osteoprogenitor cells
Precursor cells that replicate and differentiate into osteoblasts then osteocytes
Osteoblast cells
Production of bone
Deposit osteoid and control mineralisation
Osteocytes
Differentiated osteoblasts
Encased in the bone, produce cell bodies that lie in the lacunae
The cell processes project through the canaliculi and communicate with others via gap junctions
Osteoclasts
Reabsorb bone in remodelling
develop from monocytes, then migrate to bone surfaces, similar to phagocytes e.g. produce lysozyme to dissolve the bone
Large and multi-nucleated
Live on the bone’s surface in Howship’s Lacunae = hollows formed by own bone dissolving action
Compact bone
= cortical bone
Solid, hard, dense - forms the outer layer of most bone and has a protective function
Spongey bone
= trabecular / cancellous bone
Network of thin trabeculae/plates, seperated by marrow space.
Light and adaptable, can remodel via osteoblasts/clasts on surface (response to stress and for mineral homeostais)
Osteoperosis = brittle bones due to too little trabeculae (inc reabsorption, dec production)
Haversian canals of the Haversian system?
Central canal of each osteoid
Contains blood vessels
Lamellae of the Haversian system?
Bone laid down in concentric lamellae (layers) around the canal
Osteocytes of the Haversian system?
Housed in lacunae between lamellae
Canaliculi of the Haversian system?
Form a network between osteocytes, allows communication and nutrient access via tissue fluid within them.
Types of Cartilage
Hyaline
Elastic
Fibrocartilage
Hyaline cartilage
articular cartilage, epiphyseal plates, costo-clavicular cartilage
Elastic cartilage
Similar to hyaline with increased elastic fibres, external ear and epiglottis
Fibrocartilage
Between hyaline and tendons/ligaments
Menisci, intervertebral discs, tendon/ligament attachment points.
