Bones and cartilage
What are some functions of cartilage
Smooth articular surfacd at bony ends, shock absorber, structural support and new bone formation
What are the 2 types of lamellar bone
Spongy and compact bone
What cells secrete osteoid
osteoblasts
What can be found in the matrix?
Proteoglycans, sulphated glycosaminoglycans—keratin sulphate, chondrotin sulphate. Hyaluronic acid
Describe the process of mineralization of osteoid
1. After osteoblasts produce new matrix, they secrete glycoproteins (osteocalcin) invites calcium and phosphate ions and osteocalcin binds to them 2. Alkaline phosphatase raises calcium and phosphate ions concentrations 3. Osteoblasts secrete vesicles to create space to deposit mineral ions 4. Final product is hydroxyapatite salts
Describe endochondral ossification
1. From hyaline cartilage, mitosis occurs and cartilage calsifies. 2. Periosteal bone collar forms around diaphysis. 3. Blood vessels are invited to vasularize the developing bone and primary ossification center forms in diaphysis where osteoblasts start multiplying 4. Secondary ossification centers from in epiphyses 5. Bone replaces cartilage, except the articular cartilage and epiphyseal plates. Ends are now covered by articular cartilage while diaphysis covered by periosteum. 6. Epiphyseal plates ossify and form epiphyseal lines.
Stages of fracture healing
1. Hematoma (mass of clotted blood) forms 2. This process invites stem cells from periosteum to form cartilage cells, forming callus. 3. The endochondrial bone form process occurs, forming a bony callus (spongy bone). 4. Bone remodeling occurs where spongy is removed by hard callus, forming compact bone.
Describe intramembranous ossification
1. Ossification centers appear in the fibrous connective tissue membrane. Selected mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center. 2. Osteoid is secreted within the fibrous membrane and calsifies. Trapped osteoblasts become osteocytes. 3. Accumulating osteoid is laid down between embryonic blood vessels in a random manner, forming network of trabeculae of woven bone. Vascularized mesenchyme condenses on the external face of woven bone and becomes the periosteum. 4. Trabeculae just deep to the periosteum thicken and replaced by mature lamellar bone, forming compact bone plates. Spongy bone persists internally and it's vascular tissue becomes red marrow.
Where can you find hyaline cartilage
Articular ends of bones, costal cartilage, trachea, epiphyseal growth plate
What are the exceptions to which hyaline cartilage does not have perichondrium
Articular ends of joints, epiphyseal plate, nasal and costal cartilage
Why is cartilage repair poor
Avascular, immobility of chondrocytes, limited ability of adult chondrocytes to divide
How does cartilage receive its nourishment
Avascular, so it needs diffusion through the water in ground substance
Osteoporosis
Bone mineral density decreases, more prone to fractures (esp old ppl and postmenopausal women)
What are the inorganic components of bone
Calcium phosphate, hydroxyapatite crystals
Harvesian canals are also known as...their function
Central canal, for artery, nerve and vein to reach the bones and lined by stem cells
Where is elastic cartilage found
Ear, epiglottis
What is howship's lacuna
Empty space created after acid phosphatase dissolved matrix after being released through ruffled border
What is the inner layer that lines the bone called
Endosteum
What is appositional growth
Growth in diameter within the periosteum
What is interstitial growth in bones
Growth in length in epiphyseal plate as chondrocytes undergo mitosis
What is canaliculi
Hairlike canals that connect lacunae to each other, helps in communication between osteocytes
Another name for osteon
Haversian system
What is Goldman's canal
Horizontal blood vessels across osteons
What is woven bone
Immature mechanically weak bone, irregularly arranged collagen fibres
Chondrocytes are present in empty spaces called
Lacunae
Where are osteocytes found
Lacunae in osteoid
Types of bones formed by endochondral osteogenesis
Long, irregular and short bones
What are the functions of bones
Mechanical support, locomotion, protection, metabolic reservoir of mineral salts
What is the area between epiphysis and shaft (diaphysis) called
Metaphysis
Type of bones formed by intramembranous ossification
Mostly flat bones like clavicle, scapula, cranial bones
Does fibrocartilage have perichondrium
No
When you wear out cartilage in knees what happens
Osteoarthritis
What are bone destructing cells and their properties
Osteoclasts, multi-nucleated, contains lots of lysosomal enzymes
What is another name for bone matrix and what does it contain
Osteoid. collagen, glycosaminoglycans, inorganic mineral salts, the 3 cells, proteoglycans, matricelluar glycoproteins (osteonectin and osteocalcin)
What is periosteum made up of
Outer fibrous layer and inner cellular layers with cells that can convert into bone producing cells
What is the outer layer that covers the bone called
Periosteum
Why does bone have very good regeneration capacity
Periosteum and endosteum. Very good blood supply
What is the role of perichondrium
Surround hyaline cartilage, outer layer give support and protection, inner layer is chondrogenic
What is the most important chemical for demineralising bone in osteoclasts
Tartrate-resistant acid phosphatase
Define bone remodeling
The continual deposition of new bone tissue and the removal (resorption) of old bone tissue occurs throughout life at both periosteal and endosteal surfaces
What type of collagen fibres in bones
Type 1
Type of collagen between fibrocartilage
Type 1 and type 2 to some extent
Chondrocytes secrete the matrix and which type of collagen
Type 2
Do you have perichondrium in elastic cartilage
Yes! It's ground substance only has proteoglycans
What cells form cartilage
chondroblasts
Function of sharpey's fibres
connect periosteum to bone and attach tendon to bone
Where is fibrocartilage found
intervertebral discs, articular discs of acromial end of sternoclavicular joint, glenoid labrum, symphysis pubis
Why does bone have excellent repair ability
it contains osteoprogenitor cells in the periosteum,endosteumand marrow and it is highly vascularised
Another name for spongy bone
trabecular bone