Cartilage DLA Flashcards
What is cartilage?
Specialized type of connective tissue
- unique cells, fiber population and ground substance
- avascular
What does cartilage consist of?
95% of cartilage is extra cellular matrix(ECM)
- Solid and firm but pliable-accounts for its reliance
- allows diffusion of substances
5% cells- Chondrocytes and chondroblasts; chondroclasts
What are the functions and locations of cartilage ?
Major component of the ground substance is the glycosaminoglycans (GAGs)
-eg., chrondroitin-4-sulphate, chondroitin-6-sulphat, proteoglycans(aggrecan)
Predominant fiber type is determined by the cartilage type (hyaline, elastic, or fibrocartilage)
Functions:
- confers shape, flexibility & elasticity
- shock absorber (resistance to compression)
- tensile strength
- model for long bones formation
How much of the cartilage mass is due to cartilage cell?
Cells constitute only 3-5% of total cartilage mass
What are chondroblasts? What are they used for?
Chomdrogenic cells give rise to chondroblasts
Chondroblasts are ovoid and positioned so that their longitudinal axis lie parallel to the cartilage surface
The space occupied by a chondroblasts is called a lacuna
They synthesize cartilage matrix
Responsible for external growth of cartilage(appositional growth)
Where are chondroblasts located?
Just below chondrogenic layer of perichondrium(P)
What are Chondrocytes?
Are matured chondroblasts located in the lucanae and surrounded matrix
-Located deeper to the chondroblasts and are more spherical
- Divide by mitosis to form groups of 4-8 Chondrocytes, refferred to as isogenous groups or cell nest (CN)
- suggestive of internal growth (interstitial growth)
What are chondroclasts?
Oroginate from monocytes
Help to remodel the cartilage
What is the purpose of Chondrocytes in cartilage?
As Chondrocytes in isogenous groups mature, they move apart by their own synthesis of ECM. This results in the internal growth of cartilage
Describe Chondrocytes on electron micrograph
- irregular Chondrocytes surfaces
- extensive Golgi apparatus
- abundant rough ER
- euchromatic nucleus
- lipid droplets and glycogen deposits
How much of cartilage volume is the result of ECM?
Constitutes more than 95% of cartilage volume
What is in the ECM of cartilage?
Composed of amorphous ground substance and collagen fibers
Collagen constitutes about 15% of the total mass with Type II being the most abundant
It is not readily discernible in histological sections because some of the fibrils (type II collagen) are very fine and have the same refractive index as the ground substance.
-This gives hyaline cartilage a “glassy” appearance
What is the capsular matrix?
Matrix adjacent to the Chondrocytes
-also called paracellular matrix
What is the territorial matrix ?
Matrix found around isogenous groups
What is the inter territorial matrix?
Matrix in between isogenous groups
Highlight the composition of capsular matrix
- Highest concentration of sulfates proteoglycans, Hyaluronan, biglycans, and several multi adhesive glycoproteins
- Less collagen fibers
- Basophilic staining with H/E
Highlight the composition of inter territorial matrix
Composition is a mixture between territorial matrix and capsular matrix
Highlight the composition of territorial matrix
- Randomly arranged network of type II collagen fibrils with smaller quantities of type IX collagen
- Lower concentration of sulfates proteoglycans
- Less basophilic than the capsular matrix
Give the general composition of matrix
Sulphated groups present in GAGs, make it hydrophilic, enabling easy diffusion of nutrition to the cells
-Also provides resilience
Presence of proteoglycans provide immense strength to the matrix so that cartilage can function as a model for bone formation
What is the perichondrium?
Connective tissue covering entire cartilage (except Articular and epiphyseal hyaline cartilage and fibrocartilage)
What are the 2 layers of the perichondrium?
- Outer fibrous layer contains fibroblasts: synthesize collagen type I and matrix
- Inner circular layer/chomdrogenic layer: chondrogenic cells
Contrast the composition in layers of perichondrium
Outer fibrous layer-
- contains fibroblasts
- type 1 collagen
- blood vessels
Inner cellular layer
-source of chondroblasts
How does cartilage get nutrients?
Cartilage is avascular
Nutrients are supplied by vessels from perichondrium by diffusion, or from the synovial fluid at the Articular surfaces
