Cartilige

caritlage

bears weight and provides rigidity but flexible, avascular, contains of cells(chondrocytes), fibers and ground substances

what are the 3 types of cartilage

hyaline, elastic, fibrous

Hyaline

Type 2 collagen fibers (3x alpha )- slightly different form that is found in reticular fibers, gags, proteoglycans, multi-adhesive glycoproteins, and aggrecan. Most commonly, a strong, low-friction surface. Ribs(ventral ends), long bones(articular surfaces), nose, larynx, trachea, bronchi, fetal skelaton.

elastic

elastic fibers in addition to the matrix material of hyaline, orecin, verhoeff, van gieson, or Welgert’s stain

fibrocaritlage

abundant type 1 and 2 collagen fibers in addition to matrix material of hyaline cartilage, stains blue with mallorys trichrome. reisstant to compression and shearing combo if dense regular or ir CT and hyaline carilage . mostly fiber

Macroscopic appearance of hyaline

plates, columns, irregular masses, enclosed with fibrous perichondrium(exc), solid but flexible translucent blue to pearly

hyaline microscopic

cells embedded in a clear or lightly staining matrix, perichondrium on non-articular surfaces

perichondrium

DICT, fibers densly type 1 collagen, more cellular near cartilage, cells and fiber fade into cartilage, found near elastic and non-articular hyaline cartilage(non found around fibrous or articular hyaline cartilage)densely

matrix hyaline

stiff, basophillic, felt-work of fine collagenous fibrils, 80% water,

hyaline ground substance

multiadhesive glycoproteins, proteoglycans (aggrecan),
glycosaminoglycans (chondroitin and keratan sulfate)

hyaline fibers

most type 2 collagen

aggrecan

A cartilage proteoglycan with chondroitin & keratan sulfate chains. Its negative charge attracts water (60–80%), aiding diffusion. 100–200 molecules form large aggregates with hyaluronic acid, making cartilage matrix rich in aggrecan.

chondrocytes

Cartilage cells of mesenchymal origin (≤40 μm). Found in lacunae, singly or in isogenous groups. Produce/maintain matrix and may secrete metalloproteases. Cytoplasm is basophilic when making proteoglycans, acidophilic otherwise; clear if storing fat/glycogen.

how Chondrogenesis

Mesenchymal cells enlarge & cluster (vesicular), secrete mucinoid fluid → precartilage. Matrix plates form (honeycomb), cells become chondrocytes. Surrounding mesenchyme compresses → perichondrium. Growth is interstitial & appositional (head from neural crest ectomesenchyme).

interstitial cartilage growth

forms new cartilage within existing cartilage, divides within lacunae, deposits matrix, and interstitial growth is confined to young cartilage. also found in ribs

capsular(pericellular) matrix

youngest matrix nearest cells, stains darkly with sulfated proteoglycan, hyaluronic acid, multi-adhesive proteins

territorial (chondrin ball) matrix

stains less darkly but darker than general matrix lower conc of sulfated proteoglycans

interterrotorial( general) matrix

surrounds territorial matrix, rich in glycoproteins and proteoglycans mostly lightly staining

How does appositional growth of cartilage occur?

Adult chondrocytes have limited division/repair. Perichondrium helps: (1) Fibroblasts → chondroblasts, (2) chondroblasts deposit new matrix on old matrix surface.

regression of cartilage

with age thet die, matrix declines stains lesss darkly, calcify (this is a temp. step in endochondrial bone)

elastic cartilage occurrence

external ear, eustachian tube, epiglottis

Elastic cartilage macroscopic appearance

yellow and more opaque, flexible, and elastic than hyaline. perichondrium same as hyaline

elastic cartilage microscopic structure

Cells single or in groups, each with capsules. More cell-dense than hyaline. Matrix = hyaline cartilage + branching elastic fiber meshwork of varying thickness

fibrocartilage occurance

intervertebral disks, pubic symphysis, some in articular cartilages and capsules, where tendons attach to bones, stains best w mallorys, massons, alcian blue

fibrocartilage macro appearance

firm fibrous no perichondrium

fibroc micro stricture

single cells in rows or groups, coarse w/ type 2 and 1 or parallel with cells between fibers, always merges with hyaline or fibrous tissue