Cartilage and bone Flashcards
Cartilage
Modified connective tissue that provides support
Condrocytes
located in lacunae
Cartilage location in the body
Nose intervertebral discs associated with ribs articular surface of bones trachea/epiglottis/larynx/bronchi pinna of ear pubic symphysis
Major functions of cartilage
supports soft tissue
forms articular surfaces of bones
growth in length of long bones
Proteoglycans
composed of glycosaminoglycans (GAGs)
-linear polymers of repeating disaccharide units
Principle GAGs in cartilage
Chrondroitin 4 and 6
Keratan sulfate
Type II collagen
Forms a fibrillar scaffold
-determines tissue shape and produces tensile strength
Perichondrium
formed from mesenchyme surrounding center of chodrification
Two layers of perichondrium
Outer fibrous layer- type I collagen and Fibroblasts
Inner (chondrogenic) layer- chondroblasts
Chondrocytes
produce and secrete ECM
end up in lacunae
Cartilage is avascular
Receives nutrition from blood vessels of perichondrium
Consequences of lack of blood vessels in cartilage
Size limitation
low metabolic rate
poor repair potential of tissue
systemic treatment with drugs difficult
Hyaline cartilage
Most common form of cartilage location- ventral ends of ribs tracheal rings larynx/bronchi/trachea articular surfaces of joints epiphyseal plate nose
Elastic cartilage
Where flexible support is need external ear epiglottis several laryngeal cartilages eustachian tube
ECM- contains numerous elastic fibers
-stains with orcein dyes
Fibrocartilage
Location
- annulus fibrosus
- pubic symphysis
- a few tendons
- menisci of knee joint
ECM- increased amount of collagen causing eosinophilic appearance
No perichondrium associated with fibrocartilage
Calcification of matrix
Hyaline cartilage is most susceptible
commonly occurs during aging
Osteoarthritis
Gradual loss or change in physical properties of articular cartilage
commonly occurs during aging
Chondroma
Benign tumors of cartilage
Chondrosarcoma
Slow growing malignant tumors of cartilage
Bone function
support fleshy structures protects vital organs harbors bone barrow reservoir of Ca & phosphate involved in body movement
Periosteum
Specialized connective tissue surrounding bone
Endosteum
specialized connective tissue with osteogenic potential
-lines inner surfaces of bone
Does bone have blood vessels and nerves?
YES
Spongy bone
3D lattice of branching trabecular
-form a system of interconnected spaces filled with bone marrow
Compact bone
Composed mostly of ECM
-Lamella
Lacunae
small cavities containing an osteocyte
Canaliculi
small tubular channels
- communicate with canaliculi of adjacent lacunae
- essential for nutrition of osteocytes
- gap junctions allow ions and small molecules to pass from cell to cell
Haversian canals
Contain small blood vessels, loose connective tissue, small nerves
run parallel to long axis of bone
Volkman’s canals
Run at oblique angles to long axis of bone
-connect Haversian canals to one another and to free surface of bone
ECM Osteoid
Type I collagen
GAGs and proteoglycans
responsible for toughness and resilience of bone
Inorganic salts
thin plates or crystals of Ca phosphates
-responsible for hardness of bone
Periosteum- 2 layers
Outer (fibrous) layer
Deeper (cellular) layer
outer fibrous layer of bone
consists of dense irregular connective tissue
blood vessels which enter Volkmans canals
some collagen fibers anchor periosteum to bone
Deeper cellular layer of bone
Osteogenic potential
Osteoprogenitor cells present in adults
-not actively making bone but can be reactivated
endosteum
lines surfaces of vascular channels
covers the trabecular of spongy bone
remodeling of bone
involves activity of osteoblast and osteoclasts
Spongy (trabecular) bone is more responsive to changes in load than compact (cortical) bone
In compact bone aversion systems are formed, resorbed and replaced throughout life
Interstitial lamellae in compact bone
are persisting fragments of previous Haversian systems
Osteoclasts morphology
Small pits on surface of bone
- Large cells
- Multinucleated
- eosinophilic cytoplasm
- ruffled border
- rich in mito and lysosomes
- attached to bone by podosomes which form tight seals
Osteoclasts function
Break down of organic matrix by means of lysosomal hydrolytic enzymes
- dissolution of bone mineral by creating an acid environment
- –proton pump in membrane of ruffled border
Osteoclast origin
fusion of monocytes
osteoporosis
Estrogen levels fall @ menopause
-osteoclast activity enhanced
–bone resorption exceeds bone formation
results in skeletal fragility and increased susceptibility to fractures
Osteopetrosis
Dense, heavy bones
bone formation exceeds bone resorption
-defective osteoclasts
Osteogenesis imperfecta
Bone fragility
Osteoblasts produce insufficient type I collagen
Rickets
softening of bones
Bone matrix does not calcify normally
-due to insufficient dietart Ca or failure to produce Vit D in children
