Cartilage DLA

Question 1

What is cartilage?

Answer 1

Specialized type of connective tissue

• unique cells, fiber population and ground substance
• avascular

Question 2

What does cartilage consist of?

Answer 2

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

Question 3

What are the functions and locations of cartilage ?

Answer 3

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

Question 4

How much of the cartilage mass is due to cartilage cell?

Answer 4

Cells constitute only 3-5% of total cartilage mass

Question 5

What are chondroblasts? What are they used for?

Answer 5

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)

Question 6

Where are chondroblasts located?

Answer 6

Just below chondrogenic layer of perichondrium(P)

Question 7

What are Chondrocytes?

Answer 7

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)

Question 8

What are chondroclasts?

Answer 8

Oroginate from monocytes

Help to remodel the cartilage

Question 9

What is the purpose of Chondrocytes in cartilage?

Answer 9

As Chondrocytes in isogenous groups mature, they move apart by their own synthesis of ECM. This results in the internal growth of cartilage

Question 10

Describe Chondrocytes on electron micrograph

Answer 10

• irregular Chondrocytes surfaces
• extensive Golgi apparatus
• abundant rough ER
• euchromatic nucleus
• lipid droplets and glycogen deposits

Question 11

How much of cartilage volume is the result of ECM?

Answer 11

Constitutes more than 95% of cartilage volume

Question 12

What is in the ECM of cartilage?

Answer 12

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

Question 13

What is the capsular matrix?

Answer 13

Matrix adjacent to the Chondrocytes

-also called paracellular matrix

Question 14

What is the territorial matrix ?

Answer 14

Matrix found around isogenous groups

Question 15

What is the inter territorial matrix?

Answer 15

Matrix in between isogenous groups

Question 16

Highlight the composition of capsular matrix

Answer 16

• Highest concentration of sulfates proteoglycans, Hyaluronan, biglycans, and several multi adhesive glycoproteins
• Less collagen fibers
• Basophilic staining with H/E

Question 17

Highlight the composition of inter territorial matrix

Answer 17

Composition is a mixture between territorial matrix and capsular matrix

Question 18

Highlight the composition of territorial matrix

Answer 18

• 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

Question 19

Give the general composition of matrix

Answer 19

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

Question 20

What is the perichondrium?

Answer 20

Connective tissue covering entire cartilage (except Articular and epiphyseal hyaline cartilage and fibrocartilage)

Question 21

What are the 2 layers of the perichondrium?

Answer 21

1. Outer fibrous layer contains fibroblasts: synthesize collagen type I and matrix
2. Inner circular layer/chomdrogenic layer: chondrogenic cells

Question 22

Contrast the composition in layers of perichondrium

Answer 22

Outer fibrous layer-

• contains fibroblasts
• type 1 collagen
• blood vessels

Inner cellular layer
-source of chondroblasts

Question 23

How does cartilage get nutrients?

Answer 23

Cartilage is avascular

Nutrients are supplied by vessels from perichondrium by diffusion, or from the synovial fluid at the Articular surfaces