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Cartilage
Contains → abundant extracellular matrix and cells called → chondrocytes
Artifactual spaces around the chondrocyte called the → lacuna
Three subtypes of cartilage
(1) Hyaline Cartilage
(2) Elastic Cartilage
(3) Fibrocartilage
Hyaline Cartilage
Typically has a pale basophilic homogenous extracellular matrix and made of collagen type II fibrils (weakest)
Found supporting → walls of trachea as C-shaped rings of hyaline cartilage

Isogenous Cell Groups
Chondrocytes can proliferate, with daughter cells initially occupying the same → lacuna
New chondrocytes lay down new matrix, expanding the cartilage within in a process called → interstitial growth forming the clusters (isogenous cell groups)

Perichondrium
A layer of dense irregular CT surrounding cartilage
Divided into:
Outer fibrous layer
Most of the cells are fibroblasts
Inner chondrogenic (cellular) layer
Contain progenitor cells that give rise to → new chondrocytes

Fibrocartilage
Occurs at many sites where → tendons and ligaments attach to bone such as he annulus fibrosis of the intervertebral disc
Chondrocytes in lacunae separated by ECM containing bundles of → type I collagen fibers (give fibrocartilage extra strength)
There is a gradual transition from dense irregular CT to fibrocartilage (at sites of ligament and tendon insertion)
Bundles of type I collagen are → eosinophilic and force the chondrocytes to line up in rows between → the collagen bundles

Elastic Cartilage
Found in the epiglottis, external ear, walls of the auditory (pharyngotympanic) tube
Extracellular matrix contains → elastic fibers (eosinophilic) giving this cartilage particular resilience

Bone (also features of comapct bone)
Mature cells of bone called → osteocytes which occupy space in bone matrix called → lacunae
ECM deeply → eosinophilic
Lacunae do not line up in → rows
ECM of bone is → homogenous
Contain central canals, lacunae, osteons, canaliculi (connect osteocytes)

Osteoblasts
Bone-matrix forming cells On the surface of bone-matrix)
Relatively small with basophilic cytoplasm

Osteoclasts
Resorb bone matrix and are large, multinucleated cells
Found in depressions that they have created by restoring the bone matrix called → resorption lacunae

The Two Types of Bone Tissue
(1) Compact Bone
(2) Spongy Bone
Spongy Bone (aka cancellous/trabecular)
Found inside → irregular bone like the vertebrae, bones of the skull, and at the → ends of long bones (epiphyses)
Bone tissue is organized into thin threads called → spicules or trabeculae
Between trabeculae, there is → loose CT in young bone and with development, gets replaced with → red bone marrow

Epiphyseal Plates
Bone growth occurs by the → addition of new bone matrix at the surface of existing matrix as osteoblasts begin to deposit new matrix
Growth in length occurs at the → epiphyseal plate
Five Zones: RPHCO
Zone of Reserve
Zone of Proliferation
Zone of Hypertrophy
Zone of Calcification
Zone of Ossificaiton
Endochondral Ossification
Growth occurs by a combination of → interstitial growth of cartilage and the replacement of new cartilage with bone
