Cartilage & Bone Flashcards
What are the contents of extracellular substance in cartilage?
Collagen fibers, aggregates of Proteoglycans rich in chondroitin sulphates, glycoproteins
What are chondrogenic cells?
Stem cells for cartilage, can transform into chondroblasts
What are chondroblasts?
Build bone by actively producing components of ECS during cartilage formation
What are chondrocytes?
Mature cartilage cells, which continue to produce smaller amounts of ECS in order to maintain and strengthen the cartilage
What are the common characteristic for all cartilage types?
A vascular, ground substance rich in chondroitin sulphates, chondrocytes in lacunae, chondral territories
What are Chandra’s territories?
Lacunae surrounded by condensed ground substance
What is the perichondrium?
A layer of dense CT covering the cartilage surface. It provides the cartilage with oxygen and nutrients as it contains blood vessels.
Which layer of the perichondrium contains chondrogenic cells?
The inner layer
What is growth by apposition?
When the chondrogenic cells differentiate into chondroblasts, which then deposit additional layers of ECS on the existing surface, leading to an increase in the tissue’s overall size or thickness. (MORE ECS)
What is interstitial growth?
Growth from within, when the chondrocytes divide in lacunae and produce ECS. (MORE CELLS)
What are the main features of hyaline cartilage?
Has chondral territories, collagen type II, ground substance rich in aggrecan
What are the mechanical properties of hyaline cartilage?
Resistance to compression resulting from properties of highly hydrated proteoglycans (aggrecan)
What are the key features of elastic cartilage?
Has chondral territories, collagen type II, network of elastic fibers, ground substance
What are the mechanic properties of elastic cartilage?
Elasticity
What are the key features of fibrocartilage?
Few chondral territories, collagen type I, small amount of ground substance, no perichondium —> cannot grow appositionally
What are the mechanical properties of fibrocartilage?
Resistance to stretch
What are the main components of ECS in bone?
HA crystals, collagen type I fibers, ground substance (osteoid) with proteoglycans and glycoproteins
What is the function of osteonectin?
Binds HA crystals to collagen
What is the function of osteocalcin?
Binds Ca, participates in mineralization
What is the function of osteopontin?
Binds cells with ground substance
What is the function of bone silo protein II?
Strongly promotes mineralization
What is the function of bone morphogenic proteins?
Promote differentiation of osteoblasts, induce formation of new bone
What type of junctions are the long processes of osteocytes connected by?
Gap junctions
How do osteocytes get oxygen and nutrients?
Oxygen and nutrients diffuse via canaliculi into lacunae, where osteocytes reside
What are the key features of quiescent (resting) osteocytes?
Most numerous, poorly developed organelles, produce small amounts of ECS
What are the key features of resorptive osteocytes?
Contain lysosomes which bread down the surrounding ECS by releasing proteinases, liberate Ca ions
How can the activity of osteocytes connected close to each other be coordinated?
By exchange of chemical signals through gap junctions
What are the key features of osteoclasts?
Bone marrow-derived, multinucleated, resorb bone, ruffled border
How do osteoclasts digest bone?
- They seal off the space beneath the ruffled border by integrity ring, 2. They release H+ ions (acidification & dissolution of HA crystals), 3. They realest lysosomal enzyme for extra cellular digestion, 4. The endocytose predigested bone fragments and digest them intracellulary
How do osteoblasts control the differentiation and recruitment of osteoclasts?
- Bone marrow stromatolites cells send out M-CS. 2. M-CS makes osteoprogenitor cells express RANK-receptors. 3. Osteoblasts express RANKL. 4. RANKL binds to RANK-receptors. 5. Osteoprogenitor cells transform into osteoclasts and digest old bone
What are bone lamellae?
The structural units of mature (lamellar) bone
What 2 types of bone are there?
Spongy (cancellous) and Compact
What is spongy bone built of?
Interconnected networks of bone trabeculae
What is compact bone made of?
A compact array of parallel osteoblasts formed around Haversian canals
What is the periosteum?
A layer of dense CT containing blood vessels, osteoprogenitor cells, and inactive osteoclasts
What is the endosteum?
A single layer of flat cells lining the inner surfaces of bone. It’s function is to support and protect the bone tissue
