Exam 1: Cartilage Flashcards
Cartilage characterisitcs
A type of connective tissue
Embryonic origin - mesenchyme
Avascular tissue
Slow at healing
Cartilage functions (4)
Tensile and compressive strength
flexible and resilient to deformations
Structural support for soft tissues
Distribution and dissipation of stresses
Extracellular matrix components
Type II collagen
Elastin fibers
Ground substance
Why isn’t collagen type I seen in histological sections
Reflexive index similar to that of ground substance
Ground substance
Sulfated glycosaminoglycans (GAG)
Hyaluronic acid
Water
ECM characteristics
Inhomogeneous distribution of GAG
When stained, it is separable into pale and darkly areas
Interterritorial matrix
Pale part of EMC
Low GAG
Territorial matrix
Darkly part of ECM
High GAG
Cells of cartialge
Chondroblasts - reside in perichondrium and produce ECM
Chondroblasts trapped in EMC (in lacunae) mature into chondrocytes
Perichondrium
Peripheral layer of vascularized, dense, irregular connective tissue that surrounds hyaline and elastic cartilage
Layers of perichondrium
Outer fibrous layer - Type I collagen fibers, fibroblasts, blood vessels, nerves
Inner chondrogenic layer - undifferentiated mesenchymal cells –> differentiate into chondroblasts that secrete external cartilage matrix
What types of cartilage lack a perichondrium
Articular hyaline cartilage
Fibrocartilage
Hyaline cartilage
Most common type
Forms most of developing skeleton (endochondral ossification)
Contains fine type II and type III (reticular) collagen fibers
Firm but flexible structural support
May calcify with age
Isogenous groups
In hyaline cartilage
2-4 chondrocytes in small clusters within same lacunae due to cell division
Where is hyaline cartilage found
Embryonic bone templates Growth plate Articular cartilage Larynx Tracheal rings Bronchi Costal cartilage Nose
Zones of articular hyaline cartilage
- Superficial zone - elongated and inactive chondrocytes, collagen parallel to joint surface
- Middle/transitional zone - spherical chondrocytes, collagen aligned randomly
- Deep/radial zone - chondrocytes in columns, collagen vertical (perpendicular?) to joint surface
- Tidemark - interface between calcified and non calcified cartilage layers
- Calcified cartilage zone - collagen insert into calcified cartilage, transition to bone
Hyaline cartilage - growth plate
Responsible for interstitial growth
Zones of growth plate
- Reserve cartilage zone
- Cell proliferation zone -
- Cell hypertrophy/maturation zone
- Calcification zone
- Bone deposition zone
Growth plate - Reserve cartilage zone
Resting chondrocytes
Type II collagen randomly oriented
Closest to epiphyseal end and high oxygen tension (near epiphyseal blood supply)
Growth plate - Cell proliferation zone
Chondrocytes divide, creating columns of flattened lacunae
Collagen form longitudinal septa (walls) in between lacunae
Growth plate - Cell hypertrophy / maturation zone
Low oxygen tension - chondrocytes stop dividing and start hypertrophying
Cartilage walls between lacunae are thinning
Growth plate - Calcification zone
Mineral deposited in collagen matrix between chondrocytes columns
Cartilage calcified (only temporary support)
Growth plate - Bone deposition zone
Chondrocytes die and horizontal walls between lacunae breakdown
Osteoblasts arrive and start to deposit osteoid on calcified cartilage, creating primary spongiosa
Closest to metaphyseal end
Growth plate - metaphysis
Osteoblasts deposit concentric lamellae which will create secondary spongiosa (trabeculae)
Concurrently, chondroclasts remove the temporary mineralized cartilage
Groove of Ranvier
Contributes chondrocytes to growth plate for growth in diameter (appositional growth)
Prone to damage
Ring of LaCroix
Provides mechanical support for weak bone-cartilage interface of the growth plate
Protects Groove of Ranvier from damage
Growth plate - formation of cortex
Similar to what happens in intramembranous ossification
Spongiosa close to perimeter of bone continues to ossify and becomes cortex
Growth plate fusion
Cycle of chondrocyte divisions and hypertrophy pushes reserve cartilage toward epiphysis and so the bone elongates
When reserve cartilage depleted, bone stops elongating and growth plate is closed –> fused
In what animal does the growth plate never fuse
Rodents - grow throughout life
Elastic cartilage characteristics
Similar structure to hyaline cartilage, plus branching elastic fibers
Very flexible
Continues growing throughout life
Affected by gravity
Where is elastin cartilage found
Areas of high movement
Epiglottis
Larynx
Ear pinna
Auditory tube
Fibrocartilage characteristics
Alternating layers of hyaline cartilage matrix (collagen type II) and dense connective tissue (collagen type I)
Collagen fibers oriented in direction of stress
Provide tensile and compressive strength
Resist deformation
Lacks perichondrium
