Cartilage and Bone Flashcards
Cartilage consists of
cells (chondrocytes), ground substance, extracellular fibers
Histology of cartilage
pink background- matrix; dark pink and provides blood supply- perichondrium; gaps- lacunae housing the chondrocytes
Shock absorbing characterstic of hyalin cartilage
Due to water binding to negatively charged proteoglycans and is squeezed out of cartilage upon compression and comes back and binds to proteoglycan again when relaxed
Rigidity of hyalin cartilage
Due to interactions between type 2 collagen fibrils and GAGs
GAG
glycosaminoglycans: proteoglycans in cross linked matrix with hyaluronic acid
matrix components of cartilage
GAGs (chondroitin 4 sulfate, chondroitin 6 sulfate, keratan sulfate, and hyaluronic acid) and adhesive molecule (chondronectin)
synthesis of GAG
amino acids put together in the RER and sugars added in golgi apparatus
cartilage nutrition
cartilage lacks vasculature so nutrients must come in through diffusion; nutrients provided via perichondrium
3 types of bone cells
osteoblasts, osteoclasts, osteocytes
two types of long bones
compact, lamellar, or cortical bone; cancellous (trabecular) bone
compact bone
lamellar, cortical; dense area without cavities
cancellous bone
3-d lattice of branching bony spicules, forming tabeculae around narrow spaces
geography of long bone
epiphyses- two ends
diaphysis- shaft
metaphysis- growth plate between epiphyses and diaphysis
composition of bone matrix
35% organic matrix and 65% inorganic salts
organic matrix of bone
35% of bone; extracellular organic phase, composed of proteins (exogenously derived and trapped growth factors), glycoproteins, and proteoglycans synthesized by the osteogenic cell;
consists of type 1 collagen fibers (85-90%) embedded in an amorphous ground substance
inorganic content
65%; hydroxyapatite crystals [Ca10(OH2)(PO4)6]
osteoprogenitor cells
pluripotential, stem cells from mesenchyme; can differentiate into osteogenic cells-osteoblasts; found in periosteum and endosteum as bone lining cells and differentiate into osteoblasts following a fracture
osteblasts
synthesize and secrete the organic matrix of bone: type 1 collagen and non collagenous proteins and alkaline phosphatase
osteocytes
calcified osteoblasts; communicate via gap junctions
osteoclasts
multinucleated cells derived from monocytes; produce an acidic environment ideal for dissolution of bone matrix; plasmalemma of the osteoclast is thrown into folds and villous like processes constituting the ruffled border
origin of bone cells
mesenchyme–> osteoprogenitor –>osteoblasts (–> osteocytes) OR bone lining cells (stem cells);
bone marrow monocyte precursors–> monocytes–> osteoclasts
osteoblasts synthesize
osteoid, alkaline phosphatase, noncollagenous proteins
osteoid
type 1 collagen and proteoglycans
noncollagenous proteins synthesized by noncollagenous proteins
RANK-L- stimulated osteoclastogenesis Osteoprotegerin inhibiting factor- decoy receptor for RANK-L growth factors osteocalcin- mineralization osteopontin- forms sealing zones