cartilage structure and function Flashcards
what are the 3 components of cartilage?
- cells (chondrocytes)
- matrix (fibres and AGS)
- perichondrium
is cartilage vascular or avascular
avascular
what type of tissue is cartilage
CT
what are the cells in cartilage and what is their function
- cells = chondrocytes
- chondrocytes differentiate from mesenchymal stem cells
- they synthesise and secrete extracellular matrix
- form isogenous groups when devided in lacunae.
- there is single or multiple chondrocytes in one lacunae.
- chondrocytes undergo cell division
- have spherical nuclei
what is the matrix of cartilage
- fibres and ground substance
- mainly collagen type II in hydrated gel of preoteoglycans and structural proteins which provide strength
- AGS provides the firmness of the matrix
- matrix is resistant to compression, strong - almost rigid, acts as a medium for diffusion of nutrients to chondrocytes.
- avascular
what is the structure of a proteoglycan
- core protein with GAGs attached
- contain many associated water molecules.
- regulates size of molecule movement
what is a GAGs
- glycosaminoglycans
- hyaluronic acids
- negatively charged and therefore attact water
perichondrium structure and function
- fibrous layer –> outer sheath of dense CT
- surrounds cartilage (except for articular chartilage and joints of fibrocartilage)
- provides protection and attachement to adjacent structures
- contains capillaries –> source of nutrients –> needed for growth and maintanance.
what are the 3 types of cartilage
- hyaline cartilage
- elastic cartilage
- fibrocartilage
function of hyaline cartilage
- shock absorption
structure of hyaline cartilage
- perichondrium
- outer fibrous layer = structural supprt
- inner cellular layer = gives rise to chondrocytes - Matrix
- AGS, protroglycans, glycoproteins
- type II collagen fibres - Chondrocytes
- located within lacunae
- can divide
- in isogenous groups
location of hyaline cartilage
- epipheseal plate = end of long bones –> increases bone length, plate disappears when individual has fully grown.
- in ribs, nose, and trachea
- at growth of bones
- endochondral ossification = bones first appear in fetus as hyaline cartilage
- articular cartilage = between joints and points of articulation; no perichondrium
function of elastic cartilage
- flexible support
- resistant to deformation due to firm structure –> maintians shape of structure
structure of elastic cartilage
- perichondrium present
- matrix of hyaline cartilage (chondrocytes, matrix, and perichondrium) + elastic fibres.
- matrix contains type II collagen fibres
location of elastic cartilage
- does not contain epiphyseal plate.
- external ear
- epiglottis
- larynx
function of fibrocartilage
- resistance to compressive forces and stress
- the strongest out of the 3 cartilage types - immoveable
structure of fibrocartilage
- combination of dense regular CT and hyaline cartilage (alternating layers)
- collagen type I and II
- no perichondrium
location of fibrocartilage
- joint capsules
- intervertebral discs
- ligaments
what is interstitial growth
- growth of bone in length
- expands within ECM via division of chondrocytes –> production of matrix
what is appositional growth
- bones grow in width - bone thickening
- addition of new cartilage at surface
why does cartilage have limited repair ability if damaged
- chondrocytes are bound to lanuae :. cannot bigrate to damaged areas
- cartilage does not have a blood supply therefore, deposition of new matrix is a slow process.
what are the 3 types of joints
- diarthroses = freely moveable
- synovial joints (shoulder joints, TMJ) - amphiarthroses = slightly moveable
- cartilaginouse (pubis) - synarthroses = immoveable
- fibrous (sutures of the skull)
what cartilage is in the synovial joints
articular cartilage (type of hyaline cartilage)
what is gomphosis and what type of joint is it
- dentoalveolar joint
- type of synarthrosis joint
what is the compostion of bone
organic and inorganic
- organic composition - OSTEOIDS - cells, collagen fibres (30%)
- type I collagen fibres organsied in a lamellae (ring-like)
- resists tensile strength, bending and torsional forces - iorganic composition - HYDROXYAPATITE minerals (60%)
- calcium and phosphorus crystals arranged in a protein matrix
- resists compressive forces
what are the 3 components of bone
**1. periosteum **
- on the periphery
- outer CT covering of the bone (except for on the articular cartilage)
- outer periosteum = site of muscle, tendon and ligament attachement.
- inner cellular layer = contains capillaries and source of osteoprogenitor cells –> gives rise to osteoblasts
**2. endosteum **
- “endo” = within
- lines the internal cavities of the bone
- Covers trabeculae in spongy bones
3. bone marrow
- in all internal spaces of the bone.
- yellow bone marrow (in dyaphysis) = fat cells, capillaries, only in adult bone.
- red bone marrow (in epiphysis) = myeloid tissue (blood cells, some fat cells and large capillaries), within cavities of spingy bone.
what are osteoprogenitor cells
- precursors to osteoblasts and differentiate into thm under the influence of growth factors.
osteoblasts
- synthesise bone matrix – osteoid (collagen type I, proteins and hydroxyapatite) –> makes osteoid
- mature into osteocytes
- derived from mesenchymal cells
- cuboidal cells and uninucleated
osteocytes
- structure = stellate shaped, single nuclei, in lacunae, cytoplasmic processes in canaliculi and joined by gap juntions.
- present within lacunae within bone
- contain cellular processes that reach out to other osteocytes for communication
- maintanence of bone matrix
- responds to mechanical stress - regular bone remodelling
osteoclasts
- derived from monocytes
- responsible for bone resorption
- Howships lacunae via brekadown of bone.
what is the haversian system
- AKA osteon
- ## structural unit of compact bone
fucntion of bone
- support = vertebbral colmn supports weight if body and distributes weight
- protection = protect the brain, organs, spinal cord,
- calcium and phosphorus storage
- blood formation = via red bone marrow
- triglyceride storage = via yellow bone marrow
fucntion of bone
- support = vertebbral colmn supports weight if body and distributes weight
- protection = protect the brain, organs, spinal cord,
- calcium and phosphorus storage
- blood formation = via red bone marrow
- triglyceride storage = via yellow bone marrow
- compact bone resists torsioanl stresses
- spongy bone resists compression
how do compact bone communicate
- osteocytes send out cellular processes within canaliculi to other osteocytes –> movement of nutrients via haversian canals through osteoblasts –> communication via gap junctions.
structure of compact/cortical bone
- closely packed osteons/haversian systems
- concentric lamellae
- osteocytes in lacunae
- haversian (central) canals –> contains nerve and blood supply, lined by endosteum, in the middle of the osteon
- volksman’s canals –> channels that connect the haversian canals
- collage (type I) fibres run parallel with the lamella and perpendicular to adjacent lamellae
function of compact bone
- mechanical strength
- storage/release of calcium
- lipid storage
- 80% skeletal mass
structure of spongy bone
- network of connecting plates arranged in trabeculae
- trabeculae is lined by endosteum
- spaces between trabeculae filled with red bone marrow.
function of spogy/trabecular bone
- produces red blood cells
- 20% skeletal mass
