Cartilage Tissue Flashcards
What 4 types of tissue are focused on in histology?
Epithelium
Muscle
Connective
Nervous
What are the characteristics of cartilage in general?
Semirigid supporting tissue - strong but slightly flexible
Withstands compressive forces incurred by locomotion and weight bearing
Avascular - no lymphatics or blood vessels
Aneural
How many types of cartilage are there?
Three
What is the location of hyaline cartilage?
Nose, articular surfaces, costal cartilage, respiratory system
• translucent blue-white appearance in fresh samples
Fetal skeleton (to be replaced eventually by bone)
What is the matrix composition of hyaline cartilage?
Type II collagen
Chondroitan sulfate
What is type II collagen?
Organizes and anchors ground substance
Only found in cartilage and thinner than type I cartilage
What is chondroitan sulfate function?
Binds water and resists compression
Provides a shock absorbing quality to cartilage matrix
This matrix is non-fibrous in appearance with routine light microscopy
What are chondrocytes?
Relatively mature cells located throughout matrix
• relatively large round cells living in lacuna
What is the lacuna?
Spaces in the matrix
In what configurations can chondrocytes be located?
Maybe located individually or within isogenous groups (clusters)
What is the function of chondrocytes?
responsible for some growth and most maintenance of cartilage matrix
What are chondroblasts?
Relatively immature cells located at the periphery of the matrix
Relatively small ovoid cells at the edge of the cartilage matrix
What is the function of chondroblasts?
Contribute to the growth and repair of cartilage matrix
What is the perichondrium?
Transition tissue at the periphery of the cartilage
Contains the vasculature and provides for growth
What are the two components of perichondrium?
Chondrogenic perichondrium
Fibrous perichondrium
What does Chondrogenic perichondrium contain?
inner layer containing chondroblasts and type II collagen
What does Fibrous perichondrium contain?
outer layer containing fibroblasts and type I collagen
Is the perichondrium present in articular cartilage?
no it is absent
Where is elastic cartilage found?
external ear, auditory tube, epiglottis, parts of larynx
What is elastic cartilage made of?
Type II collagen, chondroitan sulfate
What is the function of elastic fibers in elastic cartilage?
Provide greater elasticity than hyaline cartilage exhibits
Appear as short, sinusoidal lines in matrix (usually densely packed)
Fresh samples are more yellowish than hyaline cartilage
Are chondrocytes, chondroblasts and a perichondrium present in elastic cartilage?
Yes the only difference is elastic fibers
Where is fibrocartilage located?
intervertebral disks, pubic symphisis, articular disks, menisci of knee
what is the function of fibrocartilage?
present where tough support or tensile strength is required
what type of collagen does fibrocartilage contain?
Contains both type I and type II collagen
This matrix has a uniformly fibrous appearance
What type of cartilage is the strongest?
Fibrocartilage due to the type I collagen present
Are condrocytes present in fibrocartilage?
Yes, Chondrocytes tend to be grouped and separated by bundles of collagen fibers
Is there a true perichondrium in fibrocartilage?
no true perichondrium is present
type I collagen blends with the type I collagen of bone
what are the two types of cartilage growth mechanisms?
Intersititial growth
Appositional growth
What is interstitional growth?
Growth from inside out
Process:
1) chondrocytes divide inside their lacunae
2) they separate by secreting matrix between themselves
3) this method of growth works well early on but slows as cartilage matures
4) isogenous groups are more prevalent as interstitial growth becomes less effective
What is appositional growth?
Depends on the presence of a functional perichondrium
the process:
1) perichondrial chondroblasts secrete new matrix on the existing cartilage
2) perichondrium pushes outward as a result
3) as chondroblasts lag behind the outward moving perichondrium they
become chondrocytes
Does growth mechanisms occur simultaneously?
yes both can occur simultaneously
Where does endochondral ossification occur?
in all bones except for flat bones and facial bones
What is endochondral ossification?
Hyaline cartilage replacement in the development of most long bones
What are mesenchymal cells?
Essentially stem cells that exist in the fetal areas where these bones will form.
These are multipotential cells capable of becoming a variety of cell types
what do some fetal mesenchymal cells initially differentiate into to start the endochrondal ossification process?
Chondrogenic cells
What do chondrogenic cells divide into?
chondroblasts
what do chondroblasts initially produce ?
a hyaline cartilage model of bone
Chondroblasts have a peripheral perichondrium (both chondroblasts and mesenchymal cells)
will grow in size by both intersitial and appositional growth
where do blood vessels start developing?
In the surrounding mesenchyme at the same time as hyaline cartilage
what changes do the developing vasculature cause to the periphery of the cartilage model?
Cartilage cells start dying and are replaced by bone cells
Results in a conversion of the peripheral cartilage matrix into bone matrix
do blood vessels eventually grow through the perichondrium? if yes, where?
yes, they grow through the perichondrium at about the mid-diaphysis
What creates the primary ossification center in the diaphysis?
when blood vessels grow through the perichondrium at about mid-diaphysis
What does the blood vessel that succeeds in the diaphysis of the bone eventually turn into?
The nutrient artery for the bone
What cells are brought into the primary ossification center to start developing bone cells?
mesenchymal cells
in the vascular environment, what do mesenchymal cells differentiate into?
Osteogenic cells
What do osteogenic cells divide to produce?
Osteoblasts
What do osteoblasts do in endochondral ossification?”
begin secreting new bone matrix on the old cartilage matrix
what does the vasculated primary ossfication center lead to?
leads to cartilage cells dying off and in their absence the remaining cartilage matrix begins to calcify
What do the osteoblasts secrete in the primary ossification center?
secreting osteoid on the remnants of the calcified cartilage matrix
what is osteoid?
the initial, unmineralized version of bone matrix
What causes the osteoid to eventually become mineralized?
hydroxyapatite
What does the ossification process eventually create?
The bone eventually thickens peripherally into compact bone
The cancellous bone in the central region is subsequently resorbed, leaving a marrow cavity which later is populated by hemopoietic tissue (blood forming cells)
When and where does the secondary ossification center develop?
Develops in each epiphysis and most develop postnatally when a blood vessel grows into the epiphysis. The process of cartilage replacement mimics what is seen in the primary ossification center
How does hyaline cartilage end up on articular surfaces?
Hayline cartilage is actually what is leftover after the rest of the cartilage has calcifies into bone
What are epiphyseal plates?
Transverse disk of cartilage between diaphysis and epiphysis.
Required for postnatal lengthening of bone (Growth Plate)
What are the zones in early epiphyses and epiphyseal plates?
zone of resting cartilage Zone of proliferating cartilage Zone of hypertrophied cartilage Zone of calcifying cartilage Zone of ossification
What are the characteristics of the zone of resting cartilage?
Primitive hyaline cartilage
Cartilage cells are evenly distributed throughout zone
Uniformly small cells and not actively dividing
Not producing much matrix
What are the characteristics of the zone of proliferating cartilage?
Cartilage cells here are rapidly dividing
Very active interstitial growth
Many isogenous groups visible
Large areas of newly produced matrix
What are the characteristics of the zone of hypertrophied cartilage?
Also called “maturing cartilage”
Large swollen cartilage cells (still located within isogenous groups)
These cells are dying
What are the characteristics of the zone of calcifying cartilage?
Cartilage cells have died and washed away
In their absence, matrix starts to change
Calcium accumulates in cartilage matrix
Matrix changes color from pink to blue
Perfect environment for bone to grow
What are the characteristics of the zone of ossification?
Osteoblasts land on calcified cartilage
Convert it to bone
Bone stains a distinctive red
Where does the majority of interstitial ossification occur?
In the proliferating zone
How do bones widen?
Through appositional growth originating in the endosteum and periosteum
What causes bones to lengthen?
Continued interstitial growth in epiphyseal plate cartilage
Balanced by loss of cartilage (calcification) on diaphyseal side of plate
Eventually cartilage replacement exceeds cartilage production leading to ossification
no further lengthening is possible after this happens
What do osteoblasts make?
Bone matrix (osteoid, primitive bone)
What is intramembranous ossification used to form?
flat bones and facial bones
What causes mesenchymal cells to differentiate into osteogenic cells?
early vascularization
what are osteogenic cells and what do they divide into?
stem cells that divide to produce osteoblasts
What are the steps that osteoids take to reach bone?
osteids -> mineralized osteoid -> bone
how does trabecular bone form?
Through remodeling
What develops blood vessels and contributes to hemopoietic bone marrow?
intervening residual mesenchyme
how does the complete plates of bone form in flat and facial bones?
Increased bone formation on the inner and outer surfaces
what happens when bone is treated by an acidic solution?
the inorganic matrix is removed
what happens when bone is treated by an extreme heat?
organic material is removed
What is compact bone also known as?
Cortical bone
what is compact bone?
hard outer shell seen particularly well in diaphysis of long bones
what is the function of compact bone?
functions to “carry the load”
what is the periosteum?
transitional tissue on the outer surface of compact bone
what is osteogenic periosteum?
Adjacent to compact bone with osteoblasts
- provides for outward appositional growth
what is Fibrous periosteum?
peripheral layer with fibroblasts
What is the endosteum?
inner cellular layer (no fibrous layer) lining the marrow cavity
- provides for inward appositional growth
what is spongy bone also known as?
Travecular or cancellous bone
what is spongy bone?
Anastomosing lattice of bony spicules in the epiphysis and marrow cavity
What is the function of spongy bone?
functions to “distribute the load”
Where is lamellar bone found?
Found in both compact and spongy bone
What is the alignment of the collagen of lamellar bone?
Regular parallel alignment of collagen in sheets
what is woven bone?
Fetal form of bone and also seen during wound repair
What is the alignment of the collagen of woven bone?
collagen is layed down in a very irregular fashion
temporary condition which will later be remodeled into lamellar bone
What is the proferred condition of bone?
lamellar bone because the organization results in strength
what zones are there in synovial joint?
Superficial zone intermediate zone deep zone tidemark calcified zone
what is the superficial zone in synovial joint?
flattened chondrocytes adjacent to the synovial fluid
- collagen bundles oriented parallel to articular surface create smooth surface
what is the intermediate zone in synovial joint?
Round, evenly distributed chondrocytes
- disorganized collagen bundles permit deformation in response to load
- fluid readily moves in/out of this zone in response to load
- fluid exchange provides a vehicle for metabolic exchange for chondrocytes
what is the deep zone in synovial joint?
clustered chondrocytes near the epiphyseal bone
- responsible for interstitial growth to maintain articular cartilage
what is the tidemark in synovial joint?
transition line between deep zone and calcified zone
what is the calcified zone in synovial joint?
Layer of calcified cartilage matrix adjacent to epiphyseal bone
- Results from very slow but perpetual endochondral ossification
- collagen fibers oriented perpendicular to surface anchor cartilage to bone
What is the process of articular cartilage calcification?
1) Begins with small deposits ofcalcium salts
2) These coalesce as they increase in size
3) Interferes with adequate diffusion to/from chondrocytes
4) Chondrocytes die and cartilage matrix is slowly resorbed with eventual erosion to the subchondral bone
What is the stratum fibrosum?
outer portion of joint capsule comprised of dense irregular CT
Joint capsules vary in thickness which correlates with the amount of stability or mobility it provides?
True
Where does the stratum fibrosum transition to fibrocarilage?
At insertion points on bones
The stratum fibrosum is richly vascularized but poorly innervaed, true or false?
False, it is poorly vascularized but richly innervated with proprioceptive nerve endings
What is the stratum synovium?
inner lining layer of capsule
What is the intima in the stratum synovium?
1-3 layers of specialized fibroblasts
What are the specialized fibroblasts in the intima of the stratum synovium known as?
Synoviocytes
What are synoviocytes function?
responsible for producing and recycling synovial fluid and removing debris
What is the subsynovial layer of the Stratum Synovium?
the highly vascular supporting Connective Tissue layer for the intima
What is synovial fluid?
thin fluid film that coats articular surfaces and the stratum synovium
What is the function of synovial fluid?
Lubricates internal joint surfaces to reduce friction
Provides a medium for metabolic transport to/from articular cartilage chondrocytes
