Part B
Bone Structure
Bones
• Bones are organs!
– Contains various types of tissues
• Osseous tissue (dominates)
• Nervous tissue
• Cartilage
• Fibrous connective tissue (lining
cavities)
• Muscle and epithelial tissues in
blood vessels
Bones
• We will look at bone structure
on three levels
•Gross
•Microscopic
•Chemical
Gross Anatomy
Bone Markings, Bone
Textures, Bone
Structures
Bone Markings
• Surface features of
bones
– Sites for attachments for
muscles, tendons and
ligaments
– Joint surfaces
– Passages for nerves and blood
vessels
Bone Markings
• Categories of bone markings
– Projections
• Bulges that grow outward from
the bone surface
– Depressions and openings
• Indentations, holes, and cavities
Projections That Are Sites of
Muscle and Ligament Attachment
• Tuberosity – rounded projection
• Crest – narrow, prominent ridge of bone
• Trochanter – large, blunt, irregular
surface
• Line – narrow ridge of bone
• Tubercle – small rounded projection
• Epicondyle – raised area above a condyle
• Spine – sharp, slender projection
• Process – any bony prominence
Projections
That help to Form Joints
• Head – bony expansion carried on a
narrow neck
• Facet – smooth, nearly flat
articular surface
• Condyle – rounded articular
projection
• Ramus – armlike bar of bone
Depressions and Openings
Allowing Blood Vessels & Nerves to Pass
• Meatus – canal-like passageway
• Sinus – cavity within a bone
• Fossa – shallow, basinlike
depression
• Groove – furrow
• Fissure – narrow, slitlike opening
• Foramen – round or oval opening
through a bone
Bone Textures
• Compact bone – dense outer layer
– Looks solid to the eye
• Spongy bone – honeycomb or
spongy appearance
– Has small needle-like or flat
pieces called trabeculae
• filled with red or yellow bone
marrow
Structure of Long Bone
• General structure of Long
Bones
–Diaphysis
–Epiphyses
–Membranes
Structure of Long Bone
• Diaphysis
– Shaft
constructed
of a thick
collar of
compact bone
that
surrounds the
medullary
cavity
Structure of Long Bone
• Medullary Cavity
– Cavity of the shaft
– Contains yellow
marrow (mostly fat)
in adults
– Contains red
marrow (for blood
cell formation) in
infants
Structure of Long Bone
• Epiphyses
– Expanded ends of long
bones
– Exterior is compact
bone, interior is spongy
bone
– Joint surface is covered
with articular cartilage
– Epiphyseal line separates
the diaphysis from the
epiphyses
Structure of Long Bone
• Articular cartilage
– Covers the
external surface
of the epiphyses
– Made of hyaline
cartilage
– Decreases
friction at joint
surfaces
Structure of Long Bone
• Epiphyseal Line
– Remnant of
epiphyseal plate
• Disc of hyaline
cartilage that
grows during
childhood to
lengthen the
bone
Structure of Long Bone
• Membranes of
long bones
– Periosteum
– Endosteum
Structure of Long Bone
• Periosteum
– Outside
covering of the
bone
• Except joint
surfaces
– Glistening
white, doublelayered
membrane
Structure of Long Bone
• Periosteum
– Outer Fibrous layer is
dense connective
tissue
– Inner osteogenic layer
(next to bone surface)
is mostly osteoblasts
(bone germinators)
and osteoclasts (bone
breakers)
Structure of Long Bone
• Periosteum
– Richly supplied
with nerve fibers,
lymphatic vessels,
blood vessels
which enter the
diaphysis by a
nutrient foramen
(opening)
Structure of Long Bone
• Sharpey’s fibers
– Secures
periosteum to
underlying bone
– Made of collagen
fibers
– Extends into bone
matrix
Structure of Long Bone
• Arteries
– Supplies bone cells
with nutrients
Structure of Long Bone
• Endosteum
– Delicate connective
tissue
– Contains
osteoblasts &
osteoclasts
Structure of Long Bone
• Endosteum
– Covers internal
surfaces of bone
• Medullary cavity
• Trabeculae
(spongy)
• Canals through
compact bone
Structure of Long Bone
Figure 6.3
Structure of Short,
Irregular, and Flat Bones
Structure of Short,
Irregular, and Flat Bones
• Thin plates of
periosteum-covered
compact bone on the
outside with
endosteum-covered
diploë on the inside
• Spongy bone in flat
bone is called diploë
Structure of Short,
Irregular, and Flat Bones
• Have no
diaphysis or
epiphyses
• Contain bone
marrow
between the
trabeculae
Hematopoietic
Tissue
)
• In infants
– Found in the medullary cavity and
all areas of spongy bone
Location of Hematopoietic
Tissue (Red Marrow)
• In adults
– Found in the diploë of flat bones,
and the head of the femur and
humerus
– Remember, the diploë is the
spongy bone of flat bones
• Yellow marrow is found in the
medullary cavities
• Yellow marrow can revert back to
red marrow if a person becomes
very anemic and needs enhanced
red blood cell production
Microscopic Anatomy
Microscopic Structure of
Compact Bone
• Haversian
system, or
osteon
– the
structural
unit of
compact
bone
Microscopic Structure of
Compact Bone
• Each osteon is
a group of
hollow tubes
of bone
matrix, called
lamella, each
one placed
outside the
next
Microscopic Structure of
Compact Bone
• Each osteon
is oriented
parallel to
the long
axis of the
bone
Microscopic Structure of
Compact Bone
• Osteons are
like tiny
weightbearing
pillars
Microscopic Structure of
Compact Bone
• Lamella
– The weightbearing,
column—like
matrix
tubes
composed
mainly of
collagen
Microscopic Structure of
Compact Bone
• Haversian, or
central canal
– channel in
the center
of the
osteon
– containing
blood vessels
and nerves
• Volkmann’s
canals
– channels lying
at right
angles to the
central canal,
connecting
blood and
nerve supply
of the
periosteum to
that of the
central canal
Microscopic
Structure of
Compact Bone
Microscopic Structure of Bone:
Compact Bone
• Osteocytes
– Mature bone
cells
– Spider-shaped
• Lacunae
– small cavities
in bone that
contain
osteocytes
Microscopic Structure of Bone:
Compact Bone
• Canaliculi
– Tiny, hair-like
canals
– connect lacunae
to each other and
the central canal
– Forms a transport
system
Microscopic Structure of
Compact Bone
Figure 6.6a, b
Organic components and
inorganic components
Chemical Composition of Bone:
Organic
• Osteoblasts – bone-forming cells
• Osteocytes – mature bone cells
• Osteoclasts – large cells that
resorb or break down bone matrix
• Osteoid – unmineralized bone
matrix composed of proteoglycans,
glycoproteins, and collagen
Chemical Composition of Bone:
Inorganic
• Hydroxyapatites, or mineral salts
– Sixty-five percent of bone by
mass
– Mainly calcium phosphates
– Responsible for bone hardness
and its resistance to compression
Chemical Composition of Bone:
Inorganic
• Hydroxyapatites, or mineral salts
– Bone is half as strong as steel in
resisting compression and fully as
strong as steel in resisting
tension
– Bones last long after death,
sometimes many centuries
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Quiz
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