What does it do?

Bone Tissue

Compact Bone

Spongy Bone

Spaces

Trabeculae

4 Basic Types of Bone

Long Bones

Short Bones

Flat Bones

Irregular Bones

Long Bones

Length > Width

Most appendage bones

Exceptions

Short Bones

Roughly cuboidal

Carpals

Tarsals

Flat Bones

Thin

Flat

Curvy

Irregular Bones

Don’t fit

Long Bone Structure

DiaphysisEpiphysis Epiphysis

Medullary CavityYellow Marrow

Triglycerides

Epiphysis

Epiphyseal Line

Epiphyseal Plate

Bone Exterior

Joint surfaces

Everywhere else

Covered by articular cartilage

Covered by periosteum

Periosteum

Outer layer

Inner layer

Fibrous layer Dense irregular CT

Osteogenic layerOsteoblasts

Perforating fibers

PeriosteumCellular layer

Fibrous layer

OsteocyteCompact boneCompact bone

Endosteum

Endosteum

Osteoprogenitorcell

Osteoblasts

Nuclei

Osteoclast

Osteocyte

Spongy bone

Medullary cavity

Spongy bone

Medullary cavity

Endosteum lining bony canals and covering trabeculae

Perforating canal

Perforating fibers

Periosteal blood vesselPeriosteum

Osteon

Centralcanal

Lamellae

Compactbone

Spongy bone

Osteon Concentric layers of bone matrix

Surrounding a central canal

Lamellae

Microscopic Structure of Long Bone

Centralcanal

Osteon

Collagenfiberorientation

Concentriclamellae

Nerve

Vein Artery

Lacunae

Lamellae

NerveVeinArtery

Canaliculi

Osteocytein a lacuna

Centralcanal

Flat Bone Structure

Diploë

Bone Matrix

⅓ Osteoid

Collagen + Ground substanceProvides flexibility & Resists tension

⅔ Hydroxyapatite -CaP0

4 and Ca(OH)

2

Provides hardness & Resists compression

This bone:

a. Has been demineralized

b. Has had its collagen removed

Cartilagegrows here.

Cartilageis replacedby bone here.

Long Bone – Growth in LengthInterstitial growth

Calcified cartilagespicule

Osseous tissue(bone) coveringcartilage spicules

Resting zone

Osteoblast depositingbone matrix

Proliferation zoneCartilage cells undergo mitosis.

Hypertrophic zoneOlder cartilage cells enlarge.

Ossification zoneNew bone formation is occurring.

Calcification zoneMatrix becomes calcified; cartilage cells die; matrix begins deteriorating.

1

2

3

4

Childhood Growth Hormone

Stimulates epiphyseal plate activity - cartilage production and cartilage conversion to bone

Sex Hormones Estrogen/TestosteroneStimulates epiphyseal plate activity. It causes FAST conversion of cartilage to bone and SLOW production of new cartilage.

OsteogenesisBone Deposition

OsteolysisBone Resorption

Articular cartilage

Epiphyseal plate

Bone isresorbed here.

Bone isresorbed here.

Bone is addedhere.

Bone Remodeling (Appositional Growth)

Bone Deposition/Resorption depends on Blood [Ca2+]

↓ Blood [Ca2+]

Increased intestinal Ca2+ absorption

Parathyroid glands release PTH

Decreased urinary Ca2+ excretion

Increased osteoclast activity