Bone and Cartilage (1-3)

cartilage

-both appositional growth (from perichondrium) and interstitial growth (from within)

-no vasculature

-compression function

-permeable matrix

-articular cartilage has no perichondrium

cartilage characteristics

-tough and flexible- GAGs, PGs, collagen, and elastin

-high water content due to sulfates on GAGs of matrix- shock absorber!

-chondrocytes in lacunae (spaces)

types of cartilage

-hyaline cartilage: articular, rib ends

-fibrocartilage: intervertebral discs

-elastic cartilage: ear, epiglottis

cartilage- cellular level

hyaline cartilage

chondrogenesis

-tracheal ring- hyaline cartilage

-hyaline cartilage

-elastic fibers in cartilage matrix

bone

-endochondral: long bones

-intramembranous: parietal bones (skull), clavicle

bone components

-reservoir for calcium, phosphate, and ions

-calcified matrix

-contains vessels and nerves

-Harversian system- structure

-type I collagen, proteoglycans, and glycoproteins

haversian system (osteons)

-haversian canal surrounded by concentric lamellae (layers) of bone

-lacunae lie between lamellae and contain osteocytes

-lacunae are connected by canaliculi

-Volkmann’s canals are perpendicular to Harvesian canals

-dried bone

-one haversian system (osteon)

-circumferential lamellae of bone at the periosteal and endosteal surfaces

osteoclast

osteoclast electron micrograph

intramembranous bone formation

-most flat bones and mandible and maxilla

-parietal bone skull here

-NO cartilage model as base- condensations (membranes) of embryonic mesenchymal tissue

-direct synthesis of bone matrix

intramembranous bone formation

endochondral bone formation

-hyaline cartilage model

-bone collar forms

-vessels enter (VEGF)

-primary center of ossification

-secondary center of ossification after birth

-growth plate grows cartilage toward ends of bone

endochondral ossification four major zones

endochondral ossification

-cartilage growth plate

what are the mechanisms of cartilage growth?

-appositional and interstitial growth

what is the distribution of blood vessels in cartilage, and how does this relate to the nutrition of cartilage?

-blood vessels found only in perichondrium

-nutrition by diffusion through ground substance

the cementing lines that delimit the Haversian systems may appear refractile or slightly basophilic- what accounts for this basophilia?

-proteoglycans

what structures are found within Haversian canals?

-capillaries and nerves

is the osseous lamella adjacent to Haversian canal the youngest or the oldest lamella of a particular osteon?

-the youngest

what structure in mature bone is created by the zone of resportion?

-the marrow canal

what are the differences between intramembranous ossification and endochondral ossification?

-intramembranous ossification: does not use a cartilage framework, bone develops directly on or within mesenchyme; bone growth is appositional; found in irregular bones

-endochondral ossification: replaces a preexisting cartilage framework; bone lengthens through interstitial growth and changes diameter through appositional growth; found in long bones