Live in lacunae - small cavity in the matrix, “little lake”

Secrete matrix

Glycosaminoglycans (GAGS)

Territorial matrix – matrix surrounding each lacuna,

may stain differently from the…

Interterritorial matrix

There are no vessels or nerves

Nutrients must diffuse in

Not a source of pain

From perichondrium – outer layer

Source of cartilage stem cells

Articular cartilage lacks a perichondrium

Expansion from within

Matrix and cell numbers increase

Most important in young animals

Result in multiple cells in a cluster = isogenous group

hyaline

elastic

fibrocartilage

Fetal skeleton

Articular surfaces of bone

Respiratory tree - nose, larynx, trachea

Has elastic fibers between chondrocytes

Elastic fibers not visible with routine stains

Ear - pinnae, external ear canal

Cartilage mixed with dense collagen

Chondrocytes are in rows

Intervertebral disks (annulus fibrosus)

Menisci

Tendon and ligament attachments to bone

cells: osteoblasts, osteocytes, osteoclasts

matrix

collagen

produce bone

polygonal cells (in rows along surface)

secrete and mineralize osteoid (unmineralized)

10% of osteoblasts become embedded osteocytes

Live in lacunae (one cell per lacuna)

Long cell processes allow communication between cells

Multinucleated giant cells of bone marrow origin

Remove bone

Bone removal occurs along brush or ruffled border

Howship’s lacunae

= depression in bone formed by osteoclast

matrix (bone)

1. Mineral

The majority of bone is mineral

Hydroxyapatite crystal

= calcium and phosphorus (5:3 ratio)

Mineral gives bone its rigidity

2. Collagen

Polarized light required to see collagen

Gives bone its tensile strength

woven, lamellar (microscopic organization)

compact, cancellous (configurations)

Immature bone

Formed during growth and repair

Haphazardly arranged collagen fibers

Mature bone

Parallel collagen fibers

Osteons - cylinders of concentric lamellae

Haversian canals at center of osteon

Blood vessels and nerves within canal

Stronger than woven bone

Solid bone with minimal marrow

Can be woven or lamellar

Makes up cortex of bones

Trabeculae arranged in a 3 dimensional lattice

Bone marrow between trabeculae

Can be woven or lamellar (not “spongy”)

Present inside bone medullary cavity

epiphysis 

physis

metaphysis

diaphysis

marrow

periosteum

endosteum

End of bone

Covered with articular cartilage

Growth plate

Made of cartilage

Only present in growing animals

(meta = beyond)

Cone-shaped transition

Between diaphysis and epiphysis

Cylindrical shaft of bone

Contains nutrient foramen

Contains hematopoietic cells

Becomes increasingly fatty with age

Fibrous outer bony envelope

Contains osteoprogenitor cells

Involved in repair and remodeling

endochondral

intramembranous

Bones begin as cartilage models

Primary ossification centers become diaphysis

Secondary ossification centers become epiphysis

Cartilage grows, mineralizes, then ossifies

Physis remains for longitudinal growth

most long bones form this way

Resting chondrocytes

Proliferating chondrocytes

Hypertrophied chondrocytes - weakest zone

Primary spongiosa:

• Calcified cartilage 
• Woven bone 

Lamellar bone

Secondary spongiosa is all lamellar bone

Bone forms from condensed mesenchymal cells

Osteoprogenitor cells → osteoblasts

Cartilage not involved

Flat bones (skull)

synarthroses

amphiarthroses

diarthroses

Bones connected by dense collagen

Sutures of the skull

Bones connected by fibrocartilage

Intervertebral disks

Diarthrodial or synovial joints

Ends of bones covered by hyaline cartilage

Bone connected by

Ligaments – attached to bone by fibrocartilage

Fibrous joint capsule

Synovial membrane lines inside of joint

Synoviocytes produce synovial fluid (provides nutrients)