Cartilage Flashcards
What are the functions of cartilage tissue?
Physical support - resist compression and/or absorbs shock
Resist tensile or shear forces, have elasticity, or contribute to growth and development of long bones
What are the three types of cartilage?
Hyaline
Elastic
Fiberocartilage
What are characteristics of cartilage tissue?
ECM (cartilage matrix)»_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
What are the functions and locations of hyaline cartilage?
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
What is perichondrium? What are its layers?
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
Where is perichondrium not present?
None around hyaline cartilage forming articular cartilages and growth plates
What layers of perichondrium are present in actively growing cartilages?
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
What are the hyaline cartilage cells?
In perichondrium - fibroblasts and chondrogenic cells
2 resident cell types - chondroblasts and chondrocytes
What are chondroblasts?
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
What are chondrocytes?
In center of cartilage matrix.
Monitor and maintain surrounding matrix
Can revert to chondroblasts if new matrix/cells are needed
Where do cartilage cells live?
In lacunae! Fluid filled chamber. Can live alone and in isogenous group
Describe the hyaline cartilage matrix.
Fibers are collagen II fibers and collagen IV fibers (not many of IV)
Most of it is water
What is the function of collagen II and IV fibers in the hyaline cartilage matrix?
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
What is in the ground substance of hyaline cartilage matrix?
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
What are the regions of the hyaline cartilage matrix?
Capsular matrix = pericellular capsule. Anchors cell to surrounding matrix and may also protect cells from mechanical stress.
Territorial matrix
Interterritorial matrix
Histogenesis
Initial formation of a tissue from/within embryological tissues
Chondrogenesis
Formation of cartilage tissue
What are the steps of histogenesis of hyaline cartilage?
- Mesenchymal cells in embryonic CT condense in chondrification center
- Mesenchymal cells divide and differentiate into chondroblasts
- Chondroblasts synthesize and surround themselves with new matrix
- Mitosis - formation of isogenous groups
What hormones promote and inhibit chondrogenesis?
Promote - T4, testosterone, and somatotropin
Inhibit - estrogen, cortisone, and hydrocortisone
What ways can hyaline cartilage grow?
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
What are the functions and properties of elastic cartilage?
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
What are the components of the perichondrium and cartilage of elastic cartilage?
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.
What are the functions and properties of fibrocartilage?
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
What are the fibers and cells of fibrocartilage?
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)
