cartilage

• specialized connective tissue with cells, fibers, and ecm - AVASCULAR, no nerve fibers

cartilage forming cells that produce glycosaminoglycans, proteoglycans and proteins. when they get embedded in the matrix that they produce, they care called chondrocytes

embedded chondroblasts (got stuck in the matrix they made)- proteoglycans, glycosaminoglycans, proteins

by diffusions thru surrounding tissues

• based on the primary fiber type it contains • hyaline-thin collagen fibrils that are invisible with routine staining • Elastic- thin collagen fibers plus elastic fibers • fibrocartilage- prominent parallel collagen bundles that give cartilage it’s tensile strength

• thin collagen filaments • where: places they maintain lumen/space structure and prevent it from collapsing (trachea and nostrils) OR at articular surface of bone like the ventral surface of ribs articulating with the sternum (that creates a semi-flexible union) OR movable joints like the elbow or knee to reduce friction and serve as shock absorber OR at epiphyseal (growth) plates of growing bones

• mesenchymal cells- starshaped cells that condense into a ball and turn into chondrification centers • they differentiate into chondroblasts that form cartilage (ECM) and their surroundings. • chondroblasts get trapped in LACUNAE which are bubbles in the matrix • think swiss cheese- ECM is the cheese, bubbles are the lacunae and olives in bubbles are chondrocytes

• chondrocytes that later divide via mitosis • genetically uniform because they derive from a single cell • synthesize ECM and become isolated from each other by newly synthesized matrix

-fibroblasts- cells that form fibers that form collagenous connective tissue and the fibrous outer layer of perichondrium

• connective tissue CAPSULE that covers ONLY hyaline and elastic cartilage (ie not fibrocartilage) • made by mesenchymal that turn into fibroblasts

• inner cellular • outer fibrous • perichondrium is meant to be protective and supportive. it permits cartilage growth and maintenance

-inner cellular layer-chondrogenic cells that divide, differentiate into chondroblasts and form ECM therefore, cartilage grows on the SURFACE of an existing cartilage- called appositional growth (placed side to side) and the cellular layer is the layer that allows growth

-outer fibrous layer- blood vessels that supply nutrients to the cartilage, fibroblasts, collagen type I, nerves

1) interstitial 2) appositional

• during early stages of cartilage formation • in articular cartilage (b/c it doesn’t have appositional growth DUE TO NO PERICHONDRIUM!!!!- WHY HAVE AN OUTER LAYER AT A ARTICULAR SURFACE?) • in epiphyseal (growth) plates • deep within the cartilage, cells and matrix added to INSIDE of the tissue. • DONE BY ISOGENOUS GROUPS

• most cartilages • at surface of existing cartilage- added to outter surface of the cartilage • DONE BY INNER CELLULAR OF PERICHONDRIUM

-it’s ability to grow interstitially and appositionally while providing semi-rigid support

chondrogenic cells chondroblasts chondrocytes

-chondrogenic cells- arise from mesenchymal cells and can differenciate into chondroblasts (cartilage forming) and ostoprogenitor cells (bone forming)

differentiate from: mesenchymal cells in the chondrification center • differenciate from: chondrogenic cells (in inner perichondrium) • have rER, Golgi, and are basophilic • form matrix and fibers of cartilage

• grown up chondroblasts, large nucleus, and prominent nucelous with rER, Golgi, glycogen in cytoplasm • can return to being chondroblasts (via mitosis and isogenous groups) • trapped in lacuna • monitor matrix and synthesize molecules needed to maintain cartilage matrix

collagen type 2 -contains gylcosaminoglycans, glycoproteins and extracellular fluid

• has proteoglycans with 180 glycosaminoglycans wrapped around a central core protein that makes up one unit • many hyaluronan molecules are INTERWOVEN with network of collagen fibrils in the matrix to form a 3D mesh giving cartilage it’s resilience/shock absorption

95%