Embryonic Hyaline Cartilage

Chondrocytes: spherical nuclei (red), vacuolated cytoplasm, separated by little intercellular substance (pale blue)

Perichondrium: @ periphery of cartilage mass, cells are elongated and associated with collagenous fibers (dark blue)

Hyaline Cartilage

Narrow band of hyaline with perichondrium on surface

Chondrocytes: finely granular cytoplasm containing discrete vacuoles (represent fat droplets lost during preparation), surrounded by proteoglycan-rich matrix

Elastic Cartilage

Elastic fibers: large and densely packed w/in interior of cartilage

Chondrocytes: large w/in interior, smaller toward perichondrium (left and right)

Fibrocartilage

Composed of bundles of dense collagenous fibers (pink) that are regularly arranged

Chondrocytes: lie in lacuna b/w bundles (pale blue-purple), typically occur in short rows

Spongy or Cancellous Bone (Decalcified)

Details of matrix not apparent

Lacunae: previously occupied by osteocytes (small, dark areas)

Spicules of bone: separated by bone marrow

Compact or Dense Bone

Haversian Canals: run in longitudinal axis of bone, surrounded by concentric lamellae and lacunae (contained osteocytes in life), connected by Volkmann's Canals

Interstitial Lamellae: at arrows, represent remnants of haversian systems destroyed during internal reconstruction

Compact Bone

Haversian Canal: center, lacunae and canaliculi well defined but concentric nature of lamellae not visible

Osteoblasts and Osteoclasts

Spicules of bone: (blue), developing in mesenchyme

Osteoblasts: cuboidal or pyramidal shape, continuous row in relation to surface of bony trabeculae, large nuclei and markedly basophilic cytoplasm

Osteoclasts: @ arrows, multinucleated giant cells with granular cytoplasm

Sharpey's Fibers

Bone (B): osteocytes (dark blue) in lacunae

Periosteum (P)

Collagenous (Tendon) Fibers (T): penetrate periosteum (arrowheads) and enter bone matrix as Sharpey's Fibers

Adipose Tissue (a)

Intramembranous Bone Formation, Late

Developing Calvarium: two plates of bone separated by marrow cavity

Osteocytes: on outer surface of one plate, inner surface of other (at arrows) indicating active addition of bone matrix

Endochondral Bone Formation, Finger

Endochondral bone formation best visible in intermediate phalanx

Cartilage model: pale grey

Perichondrium: dark blue

Periosteal bony collar: dark purple, around center of diaphysis

Primary Ossification Center (O): w/in diaphysis

More advanced ossification at arrow

Enchondrial Bone Formation

Cartilage model shows zones of activity and establishment of cartilage columns and calcification of the matrix (dark blue)

Endochondral Bone Formation

Periosteum (P): covers developing bone

Periosteal Collar: (dark blue), encloses diaphysis

Primary Ossification Center: red due to vascularity, cells of original periosteal bud have opened wide cavities, the primary marrow spaces

Joint Cavity: at arrow

Endochondral Bone Formation

Be able to identify zones shown in class

Bone Lecture, Slide 33

Endochondrial Bone Formation

Portion of trabeculae in ossification zone is shown

Bone Matrix: (pink) has been deposited upon calcified cartilage matrix (purple)

Osteoclast: at arrown, indicates bone resorption

Secondary Ossification Center

2ry center in head of femur (C), has not formed in greater trochanter

Diaphysis w/ periosteal collar of bone (dark blue)

Epiphyseal disc at arrows

Epiphyseal Disc

2ry Ossification Center (C): ossification has spread peripherally, cartilage remains only as epiphyseal disc (D)

Cartilage Columns: at arrows

Marrow Cavity (M)

Primitive Haversian Systems

Spongy bone matrix: (blue), contains numerous osteocytes w/in lacunae, no obvious lamellar pattern

Osteoblasts: at arrows, form irregular rows; as this layer elaborates additional bone matrix and becomes incorporated within it, a further layer of osteoblases will differntiate from the primitive connective tissue-in this way, there is repeated formation of concentric lamellae to form a primitive Haversian System

Diarthrosis, Knee Joint

Epiphyses of both bones are cartilaginous and there is no distinction between articular cartilage and the main mass of each epiphysis

Joint space is limited between epiphyses by joint capsule (arrows)

Diarthrosis, Articular Cartilage

Bones of inner ear (B): covered with articular (hyaline) cartilage (C), nuclei of chondrocytes near joint surface appear flattened and more densely stained than those w/in interior of cartilage

Interface between articular cartilage and underlying bone (arrows) is irregular