Chapter 5
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Function of Bones
o Support
 Soft body organs
o Protection
 Brain, spinal cord and vital organs
o Movement
 Levers for muscle action
o Storage
o Bulges, depressions and holes serve as
 Site of attachment for muscles
o Ligaments, and tendons
 Joint surfaces
 Conduits for blood vessels and nerves
Bone marking: Projections
o Sites for muscle attachment (ligament)
o Projections from head point
 Head
 Bony expansion carried on narrow neck
 Facet
 Smooth nearly flat articular surface
 Condyle
 Rounded articular projection
 Ramus
 Arm-like bar
Depression and Opening
o Meatus
 Canal like passway (through a bone structure ear)
o Sinus
 Cavity within a bone
o Fossa
 Shallow, basin like depression
o Groove
 Furrow
o Fissure
 Narrow, stilt-like opening
o Foramen
 Round or oval opening through a bone
Bone texture:
o Compact bone
 Dense outer layer
o Spongy (cancellous) bone
 Honey comb of trabeculae long bone
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o Diaphysis (shaft)
 Compact bone collar surround medullary (marrow) cavity
 Medullary cavity in adults contains fat (yellow marrow)
o Epiphysis
 Expand ends
 Spongy bone interior
 Epiphysis line (remnant of growth plate)
 Articular (hyline) cartilage on joint surfaces
Membranes of bone
o Periosteum
 Outer fibrous layer
 Inner ostegenic laer
 Osteoblasts (bone-forming cells)
 Osteoclasts (bone-destroy cells)
 Osteogenic cells (stem)
 Secured to underlying bone by sharpey’s fibers
o Endosteum
 Delicate membrane on internal surfaces of bone
 Also contains osteoblasts and osteoclasts
Structure of short, irregular and flat bone
o Periosteum- covered compact bone on the outside
o Endosteum- covered spongy bone within
o Spongy bone- called dipoe in flat bone
o Bone marrow between the trabeculae
Location of hematopoietic tissue (red marrow)
o Red marrow cavities of adults
 Trabecular cavities of the heads of the femur and humerus
 Trabecular cavities of the diploe of flat bone
o Yellow Marrow (new born)
 Medullary cavities and all spaces in spongy bone
Microscopic Anatomy of Bones
o Cells of bones
 Osteogenic (osteoprogenitor) cells
 Stem cells in periosteum and endosteum that give rise to
osteoblasts
o Osteoblasts
 Bone forming cell
o Cells of bone
 Osteocytes
 Mature bone cells
 Osteoclasts
 Cells that break down (resorb) bone matrix
Compact bone
o Haversian system, or osteon-structural unit
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 Lamellae
 Weight bearing
 Column- like matrix tubes
o Central (haversian) canal
 Contains blood vessels and nerves
o Perforating (Volkmann’s canals)
 Right angles throughout bone
 Connect blood vessels
o Lacunae- contains osteocytes
o Canaliculi- hair-like canals connect lacunae together and central
canal
Spongy bone
o Trabeculae
 Align along lines of stress
 No osteons
 Irregularly arranged lamellae, osteocytes and canaliculi
 Capillaries endosteum- supply nutrients
Organic
o All cells, proteins, connective tissue, collagen fiber, ground
substance
Inorganic
o Hydroxyapatites (mineral salts)
 65% by mass
 Mainly calcium phosphate crystal
 Responsible for hardness and resistant to compression
The Axial Skeleton
o 80 bones
o Three major regions:
 Skull
 Vertebral column
 Thoracic cage