Cartilage/Bone Flashcards
Function of cartilage?
- shock absorber (ex. articular cartilage between two bones)
- protects ends of bones from friction
- changes shape and returns back
Chondroblast?
- young undifferentiated cartilage cell
- produces matrix
Chondrocyte?
- once chondroblast has completely surrounded itself with matrix
- mature cartilage cell
Lacunae?
- space that cells live in
- territorial matrix around cells is different from matrix surrounding
Isogenous Groups?
- all cells from mitotic division of same cell
- specific to cartilage
- matrix is soft and has lot of water to absorb shock
- gives chondrocyte space to move
- multiple cells in one lacuna until they create enough matrix to form their own lacuna
What is Perichondrium?
- layers surrounding cartilage
- outer fibrous layer
- inner chondrogenic layer (chondroblasts)
- dense irregular CT
Chondroprogenitor cells?
cells that have the ability to become chondrocytes with the correct signals to differentiate
Type of collagen in ECM of cartilage?
- Type 2 collagen specific to cartilage
- Special Fibrillar collagen (Fibrils) to link it to ground substance: (collagen type 2, type 1, and elastin)
- connectors: collagen IX, X, XI help link to ECM
Ground substance in collagen?
- Hyaluronic Acid: simple unsulfated GAG
- GAGs (chondroitan sulfate, keratan sulfate, dermatan sulfate, heparin sulfate)
- Proteoglycans (GAG side chains)
- Glycoproteins (structure-chondronectin)
- 70% is water to absorb shock
Function of Perichondrium?
- vascular supply (nutrition) for cartilage via diffusion (except articular cartilage gets nutrients from synovial membrane)
- supply of chondroprogenitor cells
- forms interface between cartilage and tissue supported
Outer layer of perichondrium?
- fibrous layer
- dense irregular CT
- contains fibroblasts and blood vessels
- bigger layer
Inner layer of perichondrium?
- chondrogenic layer
- contains chondroblasts and chondroprogenitor cells
Types of growth cartilage is capable of?
- Appositional
- Interstitial (only in cartilage)
Appositional growth of cartilage?
- differentiation of perichondral cells
- chondrogenic layer cells divide and mature and surround with ECM
- becomes wider
Interstitial growth in cartilage?
- mitotic division of pre-existing chondrocytes
- isogenous groups start dividing
- increase in length of cartilage
What is cartilage derived from?
mesenchyme
Where is Hyaline cartilage found?
- Fetal skeleton
- articular surface of moveable joints (no perichondrium b/c have synovial membrane)
- sternal ends of ribs
- trachea
- larynx
- nose
- epiphyseal plate (includes collagen types IX, X, XI)
What is elastic cartilage?
- Fibrils: collagen type 2 and elastin (elastic fibers)
- Ground substance: similar to Hyaline Cartilage
Where is elastic cartilage found?
- external ear
- external auditory meatus
- auditory tubes
- epiglottis
What is fibrocartilage?
- Collagen type 1 fibers (no type 2, exception to rule)
- very strong to handle stress and be able to change shape
- Ground substance: similar to hyaline cartilage
- no perichondrium
Where is fibrocartilage found?
- IV discs (annulus fibrosus, nucleus pulposus-hyaline)
- Insertions of tendons and ligaments into bone
- Symphysis Pubis
- Bone to bone
How are cartilage and bone the same?
- firm tissue that resists mechanical stress
- cells lie in lacunae
- mainly ECM
How is bone different from cartilage?
- bony salts in matrix (hydroxyapatite-bone)
- nutrients cannot diffuse through salt
- presence of vasculature
- lacunae linked by canaliculi
- collagen fibrils organized into lamellae (layers)
- bone cannot grow in length without cartilage
- appositional growth only (periosteal later to osteoblasts)
Osteoblasts?
- immature bone cell
- secrete matrix
- type 1 collagen, proteoglycans, and glycoproteins
Osteocyte?
- mature bone cell
- surrounded by matrix
- reside in lacunae
- canaliculi- cytoplasmic processes
Osteoclasts?
- bone marrow derivative
- reabsorb matrix with enzymes (controlled by endocrine system)
- mulitnucleated giant cells that remodel bone
- Howsips lacunae- eroded grooves from reabsorption
Bone ECM inorganic?
Inorganic components:
- Calcium and Phosphorous (largest reservoir in body)
- Hydroxyapatite crystals
- non crystalline hydroxyapatite
- magnesium
- bicarbonate
- citrate
- sodium
- potassium
What is osteoporosis related to?
- hormones
- estrogen decreases with age after menopause
- calcium starts to be removed from bone storage
Bone ECM organic components?
- type 1 collagen
- GAGs (chondroitin sulfate, keratan sulfate)
- proteoglycans
- glycoproteins (promote calcification of matrix)
Periosteum?
- outer layer = collagen fibers and fibroblasts
- inner layer = osteoprogenitor cells
Endosteum?
- single layer osteoprogenitor cells
- lines all internal cavities of bone
- bone marrow in middle
Long bone components?
- Epiphysis
- end of bone
- articular cartilage
- growth plate - Diaphysis:
- length of bone
- bone marrow - Metaphysis:
- where bone widens
- in between two above
Primary bone tissue?
- random deposition of collagen fibers
- lower mineral content
Secondary bone tissue?
- lamellar (circular) collagen fiber arrangement around central blood vessel
- Haversian system (osteon)
Bone Lamellar pattern?
- Haversian system
- Haversian canal for blood vessel
- Volkman’s canal to communicate with other systems, perpendicular - Outer circumferential lamellae
- Inner circumferential lamellae
- Interstitial lamellae
- older systems - Canaliculi
- sends nutrition to outer osteocytes, gap junctions
Intramembranous Ossification?
- Primary center of ossification: mesenchymal cells into osteoblasts
- direct mineralization of matrix secreted by osteoblasts
- flat bones (face)
Intramembranous ossification abnormalities?
Craniostenosis
- Crouzon syndrome
- Apert syndrome
Crouzon Syndrome?
- craniostenosis, exophthalmos, short upper lip
- mutation of Fibroblast Growth Factor Receptor 2
- just face
Apert Syndrome?
- skull and mid facial abnormalities
- Syndactyly- fingers stay together
- Mutation in Fibroblast Growth Factor Receptor 2
- face and fingers
Endochondral ossification?
- long bones grow longer this way
- cartilage makes length of bone through interstitial growth and then its replaced with bone
- blood vessels enter middle of diaphysis to allow for bone growth
- epiphyseal growth plate
Growth plate zones?
- Resting zone of cartilage- hyaline, mostly ground substance with cells
- Proliferative zone- rapid mitotic division, like stacks of pancakes
- Hypertrophic zone- chondrocytes grow in size, producing lot of collagen and GAGs, preparing for calcification
- Calcification zone- starting to produce bony salts, cartilage is calcified
- Ossification zone- invading blood, osteoblasts line up, trabecular bone forming, remodeling by osteoclasts and new bony matrix formed
Endochondral ossification abnormalities?
- Osteopetrosis
- Osteogenesis Imperfecta
Osteopetrosis?
- increased bone mass
- bone appears thickened in radiographs
- abnormal osteoclast not remodeling trabeculae
Osteogenesis Imperfecta?
- Brittle bone disease
- abnormality in type 1 collagen
- generalized osteopenia in radiographs
- abundance of disorganized bone in histology
Synostosis joint?
- bone united by bone tissue
- ex. adult skull, cranial vault intermembranous bone formation
Synchondroses joint?
- primary cartilaginous joint
- bones joined by hyaline cartilage
- ex. epiphyseal plate
- ex. first rib attached to sternum
Symphysis joint?
- secondary cartilaginous joint
- bones joined by fibrocartilage
- ex. IV disc, pubic symphysis
Syndesmosis joint?
- bones connected by interosseous ligament or fibrous membrane
- permits some mobility
- ex. interosseous membrane between radius and ulna
Diarthroses joint?
- ligaments and a capsule of connective tissue maintain contact at ends of bones
- permits great mobility
- connective tissue capsule encloses a sealed articular cartilage cavity
- ex. articular joints
TGF-beta type 2 receptor mutation?
- resembles osteoarthritis
- alterations in growth plate architecture
- alterations in ECM composition
What does the MMP-13/9 knockout experiment teach us about our genes?
- there is redundancy in the system
- system slowed down but fixed itself over the course of 5 months
- bones were shorter
Knockout Cbfa-1 gene?
-complete lack of ossification
Cleidocranial dysplasia?
- box shaped skull with open sutures
- hypoplastic clavicles
- ability to oppose shoulders
