Lecture 10: Bone and cartilage Flashcards
After M-CSF is released by osteoblasts, it binds ____ which causes
M-CSF receptor on monocyte, which now becomes a macrophage and expresses RANK
What does RANK do after being expressed on macrophage
Binds RANKL on osteoblast and the macrophage becomes a multinucleated immature osteoclast
Osteoclasts secrete
Cathepsin K
H+ Cl- ions
What happens when osteoblasts secretes osteoprotegerin
Osteoprotegerin binds RANKL with higher affinity than RANK
This inhibits maturation of osteoclasts
PTH blocks synthesis of osteoprotegerin
Woven bone
Occurs during bone development or repair
Produced rapidly
Haphazard collagen foundation
Less structural integrity
PTH stimulates
Differentiation of monocyte precursors to form osteoclasts
formation of ruffled borders on osteoclasts
Fibrocartilage characteristics
Increased collagen Reduced cellularity compared to hyaline No perichondrium Type I collagen Single sparse chondrocytes
Fibrocartilage location
Intervertebral discs
Pubic symphysis
Insertion of some tendons/ligaments
Closely associated with dense CT or hyaline cartilage
Sharpeys fibers
Collagen fibers derived from the outer layer of the periosteum, projecting into the outer circumferential lamellar system
Matrix of bone consists of
Organ component osteoid
Inorganic component hydroxyapatite (35-65% of matrix)
Components of cartilage matrix
Collagen type II (type I in fibrocartilage)
Hyaluronic acid
Chondroitin, keratin and heparin sulfate
Glycosaminoglycans
Osteocytes
Maintain bone matrix
Help control calcium/phosphate levels in matrix
Elastic cartilage chondrocytes
Chondrocytes are mostly located singly
Spongy bone
Trabecular/cancellous bone
3-D lattice of branching, bony spicules intertwined to form trabeculae surrounding bone marrow spaces in long/flat bones
Osteoblasts are derived from and give rise to
Osteoprogenitor cells
Osteocytes
What happens when PTH binds receptor on osteoblast
Osteoblast is stimulated to synthesize & express M-CSF and RANKL
(Monocyte-Colony stimulating factor)
Function of H+ and Cl-
Dissolve the inorganic matrix
Osteocalcin function
High binding affinity for hydroxyapatite
Calcitonin function
Reduces bone resorption
Vitamin D-3 function
Regulates expression of osteocalcin
Osteoblasts
Secrete bone matrix
Secrete collagen and catalyze mineralization
Osteoclasts are derived from
Monocyte lineage
Hyaline cartilage strength
Solid but flexible
Territorial matrix content
High glycosaminoglycan content, low collagen content
Hyaline cartilage found in
External auditory meatus Larynx Tracheal cartilages Bronchial cartilages Fetal long bones Articular ends of bones
Elastic cartilage found in
Auricle
Epiglottis
Function of Cathepsin K
Lysosomal protease involved in bone resorption and remodeling that can catabolize elastin, collagen and gelatin (organic matrix)
Major protein products of osteoblasts
Type I collagen Osteocalcin Osteonectin Osteopontin Osteoprotegrin RANKL
