Cartilage

Question 1

What are the functions of cartilage tissue?

Answer 1

Physical support - resist compression and/or absorbs shock

Resist tensile or shear forces, have elasticity, or contribute to growth and development of long bones

Question 2

What are the three types of cartilage?

Answer 2

Hyaline

Elastic

Fiberocartilage

Question 3

What are characteristics of cartilage tissue?

Answer 3

ECM (cartilage matrix)&raquo_space; cells

Ground substance mostly proteoglycans, GAGs, and multi-adhesive glycoproteins

Some collagen II fibers are present in all cartilage tissue. Elastic or collagen I may be present

No true basement membranes

Avascular - takes long time to heal

Surrounded by perichondrium - transition between cartilage and surrounding CT proper to anchor cartilage

Question 4

What are the functions and locations of hyaline cartilage?

Answer 4

Forms articular cartilages - reduces friction and provides shock absorption

Forms initial template of most of skeleton during embryonic and fetal life

Forms the growth plates in growing long bones - allows them to elongate

Connects distal (ventral) ends of ribs to sternum - semi-flexible connections help the ribcage expand and contract when breathing

Provides structural support in walls of large airways - keeps lumens patent

Question 5

What is perichondrium? What are its layers?

Answer 5

Dense collagenous CT surrounding most hyaline cartilage and all elastic cartilages.

Has outer fibrous layer - protection, support, and allows connections to other tissues. Always visible

Inner cellular (chondrogenic) layer - formation of new chondroblasts that function in cartilage formation and growth. Distinct in cartilages that are growing

Question 6

Where is perichondrium not present?

Answer 6

None around hyaline cartilage forming articular cartilages and growth plates

Question 7

What layers of perichondrium are present in actively growing cartilages?

Answer 7

Outer fibrous - dense collagenous CT, collagen I fibers, vascularized, main cells = fibroblasts

Inner cellular layer - fewer collagen I fibers, chondrogenic cells, and sometimes few chondroblasts

Question 8

What are the hyaline cartilage cells?

Answer 8

In perichondrium - fibroblasts and chondrogenic cells

2 resident cell types - chondroblasts and chondrocytes

Question 9

What are chondroblasts?

Answer 9

On outer surface of cartilage under the perichondrium.

Synthesize and secrete hyaline cartilage matrix components (make collagen II fibers and ground substance) and stem cells that divide to generate new chondroblasts.

Becomes chonrocytes when they stock synthesizing/dividing

Question 10

What are chondrocytes?

Answer 10

In center of cartilage matrix.

Monitor and maintain surrounding matrix

Can revert to chondroblasts if new matrix/cells are needed

Question 11

Where do cartilage cells live?

Answer 11

In lacunae! Fluid filled chamber. Can live alone and in isogenous group

Question 12

Describe the hyaline cartilage matrix.

Answer 12

Fibers are collagen II fibers and collagen IV fibers (not many of IV)

Most of it is water

Question 13

What is the function of collagen II and IV fibers in the hyaline cartilage matrix?

Answer 13

Collagen II - Help the cartilage resist compression and also tensile forces

Collagen IV fibrils - form a structure very similar to lamina densa layer of epithelial basal lamina

Question 14

What is in the ground substance of hyaline cartilage matrix?

Answer 14

Aggrecan - proteoglycan

300+ aggrecan monomers attach to one long hyaluronan (hyaluronic acid) to form aggregates - has negative charge so attracts osmotically active cations and water into the matrix

Proteoglycans like decorin, biglycan, and fribromodulin helps stambilize the matric

Multi-adhesive glycoproteins - hold matrix together

Question 15

What are the regions of the hyaline cartilage matrix?

Answer 15

Capsular matrix = pericellular capsule. Anchors cell to surrounding matrix and may also protect cells from mechanical stress.

Territorial matrix

Interterritorial matrix

Question 16

Histogenesis

Answer 16

Initial formation of a tissue from/within embryological tissues

Question 17

Chondrogenesis

Answer 17

Formation of cartilage tissue

Question 18

What are the steps of histogenesis of hyaline cartilage?

Answer 18

1. Mesenchymal cells in embryonic CT condense in chondrification center
2. Mesenchymal cells divide and differentiate into chondroblasts
3. Chondroblasts synthesize and surround themselves with new matrix
4. Mitosis - formation of isogenous groups

Question 19

What hormones promote and inhibit chondrogenesis?

Answer 19

Promote - T4, testosterone, and somatotropin

Inhibit - estrogen, cortisone, and hydrocortisone

Question 20

What ways can hyaline cartilage grow?

Answer 20

Appositional growth - new cells and matrix added to outer surface of cartilage (under periochondrium). Most growth for cartilages that have a perichondrium

Interstitial growth - new cells and matrix added to inside of the cartilage, in most cartilages, this growth only occurs during early stages of cartilage formation, and occurs in hyaline cartilages that lack a perichondrium

Question 21

What are the functions and properties of elastic cartilage?

Answer 21

Has properties of hyaline cartilage plus elasticity and additional flexibility.

Located in pinna of ear, epiglottis, auditory tubes - rarest type of cartilage in body

Function is flexible support for larger structures that are subjected to being bent or pulled and need to return to their original shape and position afterwards

Question 22

What are the components of the perichondrium and cartilage of elastic cartilage?

Answer 22

Perichondrium- Fibers are collagen I and elastic. Cells are fibroblasts in the outer layer and chondorgenic cells in inner layer.

Cartilage - Fibers are collagen II fibers and elastic fibers. Cells are chondroblasts and chondrocytes.

Question 23

What are the functions and properties of fibrocartilage?

Answer 23

Lots of collagen I fibers.

Compression resistance and semi-pliability of cartilage, but with additional toughness from collagen I fibers.

Located where tough support is needed for shock absorption, or to resist large compressive, tensile, or shear forces such as IV discs, pubic syphysis, and menisci of knee

No perichondrium and very little ground substance

Question 24

What are the fibers and cells of fibrocartilage?

Answer 24

Fibers are large collagen I fiber bundles and some collagen II fibers

Cells are fibroblasts that secrete fibers and ground substance during earliest stages of cartilage formation then differentiate into fibrocartilage cells (fibrochondrocytes)