Cartilage and Bone Flashcards
cartilage and bone are…
specialized connective tissue
properties of cartilage
- avascular –> doesn’t regenerate of heal well
2. lacks sensation b/c there is no dedicated nerve supply
functions of cartilage
- support: adapted to bear weight
- movement
- framework for growth of long bones
composition of cartilage
- cells (chondrocytes: cartilage cells) 3%
- multi-adhesive glycoproteins 5%
- proteoglycans 9%
- collagens: primarily type 2 15%
- water 60-80%
perichondrium
dense connective tissue that surrounds cartilage
2 layer of the perichondrium and their functions
- inner cellular layer: gives rise to new cartilage cells
2. outer fibrous layer: connective tissue layer (has blood vessels)
perichondrium is not seen in (2)
- articular cartilage
2. fibro cartilage
chondrocytes
specific cell of cartilage
chondroblasts
immature chondrocytes
extracellular matrix produced by chondrocytes contains (3)
- collagen type 2 fibers
- proteoglycans
- multi-adhesive glycoproteins
cartilage is capable of 2 kinds of growth
- appositional
2. interstitial
appositional cartilage growth
new cartilage forms on the surface of existing cartilage
-new cells derived from inner layer of perichondrium
interstitial cartilage growth
new cell forms within an existing cartilage by mitotic division
isogenous groups
clusters of chondrocytes that have recently divided (in interstitial cartilage growth)
types of cartilage (3)
- elastic
- hyaline
- fibro-catilage
elastic cartilage
- extra cellular matrix: type 2 collagen and elastic fibers
- chondrocyte arrangement: isogenous gorups
- surrounded by perichondrium
- located in the epiglottis, larynx, pinna or ear, and auditory tube
- function: shape and elasticity
hyaline cartilage
- extra cellular matrix: type 2 collagen
- chondrocyte arrangement: isogenous groups
- surrounded by perichondrium except articular cartilage
- locations: trachea, bronchi, end of ribs, epiphyseal plates (growth plate)
- function: shape and flexibility, fetal skeleton, movement in joints
fibro-cartilage
- extra cellular matrix: type 2 with type 1 added
- chondrocyte arrangement: parallel rows
- not surrounded by perichondrium
- locations: articular discs, intervertebral discs, pubic symphysis, tendon insertion
- function: resistant to compression, cushioning tensile strength
osteoarthritis
- degenerative joint disease
- pathogenesis usually unknown
- related to aging and trauma
- type 2 collagen production is inhibited
- superficial layer is affected first but can extend to the bone
- affects hyaline cartilage most
- no treatment because cartilage is not regenerative
degeneration of the intervertebral disc
- 4th disc is composed of nucleus pulpous (gelatinous material) and anulus fibrous (fibrocartilage)
- nucleus pulpous herniates though weakened though weakened anulus fibrosis
properties of bone (6)
- well vascularized and highly innervated
- mineralized: results in hard tissue that supports and protects
- protects and serves as a supporting framework
- allows movement
- site of blood cell formation
- serves as calcium and phosphorus reserves for the body
periosteum
2 layered sheath with an outer fibers layer of dense connective tissue and an inner cellular layer that covers the OUTER surface of bone
endosteum
1 layer sheath of that contains osteoprogenitor cells that covers the INNER surface of bones
macroscopic classification of bone (2)
- compact/ dense/ cortical
2. spongy/ cancellous
compact bone
- dense layer surrounding the outside bone
- well organized “osteon” system
spongy bone
-forms a layer of trabeculae (thin spicules of bone tissue) in the interior of bone
microscopic classifications of bone (2)
- primary/ immature
2. secondary/ mature/ lamellar
primary bone
- initially formed in skeleton of developing embryo and during bone repair
- irregular organization
- low mineral content
secondary bone
- organized structure replaces primary bone
- composed of concentric lamellae
- more calcified and stronger than primary bone
osteon
-structural units that make up mature bone
concentric lamella
formed by bone matrix that surround a central cavity that form osteons
haversian canal
the cavity that contains the blood and nerve supply for osteons
interstitial lamellae
remnants of previous concentric lamella between osteons
outer circumferential lamellae
outer surface of the shaft of a long bone
inner circumferential lamellae
inner circumference of the shaft of a long bone
volkmann’s canals
- channels through which blood vessels and nerves travel from the periosteal and endosteal surfaces to reach the osteons
- connect one osteon to another and run at right angles to the long axis of the osteon
composition of bone
- inorganic components- 65% of weight of bone (mineralized calcium phosphate in the form of hydroxyapetite crystals)
- collagen type 1 (majority of organic components)
- multi-adhesive glycoproteins, proteoglycans, bone specific proteins
- cells (small %)
cells of bone (5)
- osteoprogenitor cells
- osteoblasts
- osteocytes
- bone lining cells
- osteoclasts
osteoprogenitor cells characteristics
- derived from embryonic mesenchymal stem cells
- retain ability to undergo mitotic division
- function: responsive to stimuli then differentiate into bone , forming cells called osteoblasts
- location: inner periosteum layer or growing bone and endosteum lining the bone cavity
- structure: squamous shaped cells
osteoblast cells characteristics
- function: secrete type 1 collagen and bone matrix proteins which form unmineralized bone/osteoid
- capable of cell division
- location: areas where bone is being actively laid down
- structure: cuboidal shaped cell in single file along surface of bone (basophilic cytoplasm)
- communicate by gap junctions with each other and with osteocytes
- once they secrete product required for bone formation they are surrounded by bone matrix and become osteocytes
osteocyte cells characteristics
- function: maintain matrix of bone
- location: surrounded by matrix that it previously secreted as osteoblast
- respond to mechanical stimuli and can make new matrix as needed
- also have a small role in the breakdown of the matrix
- structure: flattened nucleus, overall conforms the shape of the lacunae
- occupies a lacunae and extends cytoplasmic processes through canaliculi (small canals) to contact processes of other osteocytes and bone lining
bone lining cells characteristics
- derived from osteoblast that are not actively producing bone
- function: support cells for osteocytes, and regulate calcium flow in and out of bone
- location: external and internal surfaces of bone
- structure: flat cells that cover the surface of bone
- incapable of mitotic division but capable of differentiating into osteoid secreting cells
osteoclast cells characteristics
- precursors derived in bone marrow, travel to bone and fuse to form large muti-nucleated osteoclast
- function: bone resorption, must be activated to become a resorbing cell
- structure: large, multi-nucleated cell found where bone is being formed
- location: surface of bone and occupy spaces called howship’s lacunae
mechanisms of bone formation (2)
- intramembranous ossification
2. endochondral ossification
intramembranous ossification general
bone formed by direct differentiation of mesenchymal cells into osteoblasts (clavicle, mandible, flat bone of the skull and face)
endochondral ossification general
cartilage model is the template fro bone formation (limb bones and weight bearing portion of the axial skeleton)
