CARTILAGE

What is cartilage

Cartilage is a specialized connective tisseu where ecm is the most abundant component so its rigid but flexibile

• cells located in lacunae;

• high water content;

• absence of blood vessels and nerves.

Why does cartilage have poor regenerative capacity?

Often damaged is repaired poorrly with fiborus tissue instead beacuse

• avascular;

• non-innervated;

• low in cellularity;

• dependent on diffusion for nutrients.

What is the composition of cartilage ECM

Grpund substance: gag proteoglicans ( aggregan)

Adehsive glycoproteins

Collagen type II

Why is cartilage highly hydrated?

Because proteoglycans contain negatively charged GAGs that attract water.

Aggrecan-hyaluronic acid aggregates bind large amounts of water, giving cartilage:

• resilience;

• resistance to compression;

• diffusion capacity for metabolites.

Are collagen fibers visibile in hylain

No beacuse proteoglycans covers them

Which is the most important proteoglycans

Aggrecan is the major cartilage proteoglycan.

It:

• contains many GAG chains;

• binds hyaluronic acid through linker proteins;

• attracts water;

• generates osmotic swelling pressure.

Explain the concept of tensegrity in cartilage.

Its the balance that allows cartilage to resist compression and being flexibile it is due to the tensile forse from collagenn II and the osmotic pressure swelling of aggregans

How does the ecm appears

In hyalin?

Territorial and intraterritorial?

In hyalin it has the typical gflassy appearance while in territorial is very dark ( around lacunae)

And less dark intrateritorialy

Do you have metachromasis

Yes gag neg

Which are the 3 cells of cartilage

1. Condrocytes

2. Condroblasts

3. Condroclast

Chondroblasts

Immature cartilage cells that secrete proteoglycans, gag and glycoproteins and are basophilic as they have ab. Rer and golgi as they are maturing they are trapped inhe lacuna and mature into condorcytes

What are chondrocytes

Chondrocytes are mature cartilage cells located in lacunae. Apparently with darker parts that is the ecm around lacunae

They:

• maintain the ECM;

• have lower synthetic activity than chondroblasts;

• may contain glycogen and lipid droplets.

What elemnts indicate interstitial growth

Isogenous groups that derive from the division of one single condorcytes

What are chondroclasts?

Chondroclasts are cartilage-resorbing cells similar to osteoclasts.

They:

• degrade cartilage ECM;

• express TRAP;

• participate in cartilage remodeling and ossification.

What has to be expressed for endocondrial ossfication

Trap

What surrounds cartilage, except for which kind?

PERICHONDRIUM exect from articular and for FIBROCARTIALGE

What is the territorial matrix?

• contains more GAGs;

• stains darker and more basophilic;

• surrounds chondrocytes. WHERE THERE ARE LACUNE

What is the interterritorial matrix?

The interterritorial matrix is the ECM between lacunae and isogenous groups.

It contains relatively more collagen and fewer GAGs.

LEWSS DARK

( TRA I CONFDORCYTE INTRA

MENTRE TERRITORIAL E ATTORNO AL CONDROCYTES

What is hyaline cartilage

matrix appears glassy, translucent, and homogeneous under light microscopy.

• a glassy homogeneous matrix;

• type II collagen;

• abundant proteoglycans;

• chondrocytes in lacunae.

Where do you find hyaline cartilage

• tracheal rings;

• costal cartilage;

• nasal septum;

• larynx;

• articular surfaces;

• fetal skeleton;

• epiphyseal plates.

How do you recognize hyaline cartilage histologically?

• glassy basophilic matrix;

• chondrocytes in lacunae;

• isogenous groups( INDICATING INTERSTITIAL GROWTH

• no visible collagen bundle covered by aggregan ( proteoglycan)

• perichondrium usually present.( execpt for the ARTICULAR)

Why is hylain important for embryo

Beacuse it allow sendochorndrial ossification

What is elastic cartilage?

Elastic cartilage is cartilage containing:

• type II collagen;

• abundant elastic fibers;

• proteoglycans.

It provides flexible support.

Elastic cartilage is found in?

Elastic Ear

1. External ear

2. Auditory tube

3. Epiglottis

How do you recognize elastic cartilage histologically?

• chondrocytes in lacunae;

• numerous elastic fibers;

• high cell density;

• perichondrium.

What is fibrocartilage?

Strongest type it has both dense connective tissue and cartilage parts with COLLAGE I so it resiste compression

Which collagens are found in fibrocartilage?

Collagen II for cratuoage and caolol. 1 fromthe dnese ct

What are the characteristics of fibrocartilage?

Low cell density ( elastic has high!)

Chondrocytes in row

NO PERICHONDIRUM

Thick collagen bundles

Acidophilic ECM

Where is fibrocartilage found?

• intervertebral discs;

• menisci;

• pubic symphysis;

• tendon insertions.

How do you recognize fibrocartilage histologically?

• thick eosinophilic collagen bundles;

• chondrocytes in lacunae;

• cells arranged in rows;

• absence of perichondrium.

What are the components of the intervertebral disc?

Anulus fibrosus and nucleus polposus

Anulus: outer fibrocartilaginous ring rich in type I collagen.

Nuclus: is the inner gelatinous core derived from the NOTOCHROD!

What is disc herniation?

Disc herniation occurs when the nucleus pulposus protrudes through a weak annulus fibrosus and compresses nearby nerves.

Describe the main steps of chondrogenesis.

1. Mesemnchyme condensation

2. Progenitor cells aggregate into NODULES that are in s spherical shape

3. 3. Expressing COLLAGEN II PROTOGLYCAN

4. The devolpement of the ecm allows them to be trapped into lacune and mature into condrocytes

5. The remain mesenchymal cell differentiate around into perichondrium

Whihc i s thekey factor for collagen II expression and condrocytes differentiation

SOX 9

What forms the perichondrium during chondrogenesis?

surrounding mesenchymal cells differentiate into dense connective tissue forming the perichondrium.

What interstial gorwt

Interstitial growth is growth from within cartilage through chondrocyte division and matrix deposition.

It forms isogenous groups.

As we can see in hyaline

Appositional growth

The new chrondocytes derive from the chondroblasts of INNER LAYER of the perichondrium that get the nutrients from the dense connective tissue of the perichondrium

INCREASES IN THICKNESS-

What is the perichondrium?

The perichondrium is dense connective tissue surrounding most cartilage.

It:

• nourishes cartilage;

• provides progenitor cells;

• supports appositional growth.

What is the role of cartilage in fetal skeletal development?

Hyaline cartilage forms a temporary template for many developing bones before endochondral ossification.in which bone replaces a preexisting hyaline cartilage model.

Why is cartilage important for the growth of long bones?

Cartilage remian in the EPIPHYSEAL GROWTH PLATE (is a region of hyaline cartilage responsible for longitudinal growth of long bones.)

allowing the longitudinal growth of long bones

articular cartilage? Which are the caracteristics

is specialized hyaline cartilage covering joint surfaces in synovial joints.

1. The articular cartoilage covers the synovial joints it appears SMOOTH it is nourshed by SYNOVIAL FLUID and it lacks perichondrium

Articular cartilage presents what kind of condformation? How does articular cartilage reduces friction in synovial joints

In articular cartilage we have different ZONES

1. Superficial smooth zone

2. Transitional zone with collagen fibers in different diretiins

3. Deep calcified zone near the bone!!!!

Ecm produces a lot of hyaluronic acid allowing shock absorption and lubrification

What is a synovial joint?

Synovial cavity with synovial fluid rich to absorb the sock and pressure and synovial memebrane

Articular cartilage with a deep calcified zone near the bone and a smooth superificial zone

Fibrous capsule: has a outer layer od dense connetcive tissue anf a inner synovial layer.

osteoarthritis

Is a degenerative disease of articular cartilage

• proteoglycan loss;

• cartilage erosion;

• pain;

• stiffness;

• reduced mobility.

What causes reduced mechanical resistance in osteoarthritis?

Loss of proteoglycans as aggregan reducing water retention and making cartilage not so able to resist

What usually replaces damaged cartilage?

• dense connective tissue;

• fibrocartilage;

• calcified tissue;

• bone.