Lecture 18: Bones

hyalin carilage invaded and replaced by synovial CT

• 20nm
• 50-200nm

adhesion protein (as opposed to fibronectin)

• -Major carilage proteoglycan (with chrondroitin sulfate, kereatan sulfate) bind hyaluronic acid (backbone)
• -100 million Da, size of bacterium

hyaline cartilage

• -DCT- type I
• -Outer: tpe I, fibroblasts, bv
• -Inner: chondrogenic, chondroblastsd

• New carilage added to surface of preexisting,
• differntiationS
• switch collegen types

• New carilage ass WITHIN preesisting matrix
• Division of chondrocytes--> isogenous groups
• Cells separated by secrete matrix

Calcium phosphate (HYDROXYAPITITE): crystals within matrix

• Type II
• Elastic, flexible
• Auditory canal, epiglittis, larynx, vocal cords
• DOESN'T caclify

• Both types (I & II)- DCT & cart
• intervertebral discs
• NO perichondrium

• Tension increases bone formation;
• Pressure increases bone resorption

• Organic- osteoid (80-90% type I)
• Inorganic- calcium phosphate (hydroxyapitite): 50% dry weight

• collegen- tenisile strength, elasticity (difficult to deform)
• Hydroxyapitite- stiffness

Collegen + hydrogyapitite = rigitity (= resist in all directions)

prevents calcium absorption

• child- rickets
• adult- osteomalacia- decrease stiffness, deformed bones

sCurvy- insuff Collegen, thin, fragile shaft

• maintain bone
• Regression of secretory phenotype,
• less rER, Golgi, non-dividing
• Gap junctions

• Woven, primary
• Collegen fibril interlaced, no organization, not lamellar, low mineralization

secondary--> compact, spongy

• single variable layer of: osteogenic, osteoclast, osteoblast
• Lines 3 inner surfaces: Haversion canals, bone trabeculae, compact bone

• Shaft- compact bone (dense)
• predominates
• Ends- spongy bone (cancellous) predom

• 200 nm
• Canals- surrounded by concentric lamellae of bone (ouside-->in)
• Outer boundary of H system- cement lines

spaces between H systems, remnants of older ones

H canals interconnected by these

• Cuboidal cells, secrete osteoid- eosinophilic cuz protein>>proteoglycan
• Eestablish canaliculi
• Regulate osteoclast by osteoclast-differentiation factors
• Release matriz vesicles- CA4P2--> crystallized for
• Osteocalcin

bind Calcium, ABUNDANT non-collenagenous glycoprotein, serum marker for bone turn over

• Differntaite from monocytes, multinucleate, fusion of many cells
• Attachment region-- ruffled border
• Secretory vesicles (reg by Homrones)->
• a. carbon/citrate, inc pH, dissolve CaP
• b. lysosmal hydrolases degrade matrix
• Parathyroid- inc osteoclast, promote osteoblasts secretion of osteoclast-differention factors
• Calcitonin- red osteoclasts, inhib ruffle border

• CT-->directly to Bone
• (flat bones, skull, face)

CT-->cartilage-->bone

Inhibits osteoblasts activation of osteoclast differntiation, promotes osteoclast apoptosis