CHAPTER 5
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appositional growth
articular cartilage
canaliculi
comminuted fracture
compact bone
compound fracture
compression fracture
diaphysis
epiphyseal plate
epiphyses
greenstick fracture
hematopoiesis
lacunae
ossification
osteoblasts
osteoclasts
osteocytes
osteon (Haversian system)
periosteum
rickets
sesamoid bones
Sharpey's fibers
simple fracture
spongy bone
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I.
Bones (overview)
A. skeleton subdivisions
1. axial skeleton – bones that form
longitudinal axis of body
2. appendicular skeleton – bones of limbs and
girdles
B. bone functions
1. support
a. forms internal framework
b. supports and anchors all soft organs
2. protection
protect soft body organs
3. movement
attachment for skeletal muscles via
tendons
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4. storage
a. stores fat in internal cavities
b. storehouse for minerals (> imp. is
Ca & P)
5. blood cell formation
a. also called hematopoiesis
b. occurs in marrow cavities of certain
bones
c. red marrow  blood cells
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C. bone classification
1. 2 basic types of bone (osseous) tissue:
a. compact bone – dense, looks smooth
and homogeneous
b. spongy bone – composed of small
needle-like pieces of bone & open
space
2. classified according to shape:
a. long bones
1. longer than they are wide
2. have a shaft w/ heads @ both ends
3. bones of limbs
(except wrist & ankle)
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b. short bones
1. usu. cube-shaped & spongy bone
2. bones of wrist & ankle
3. sesamoid bones –
*special type of short bone
*form w/i tendons (patella)
c. flat bones
1. thin, flattened, usu. curved
2. layer of spongy bone b/t 2 layers
of compact bone
3. most bones of skull
d. irregular bones
1. vertebrae (make up spinal col.)
2. hip bones (coxal)
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Long – yellow
Short – light green
Flat – purple
Irregular – light blue
Sesamoid – orange
Axial skeleton – red
Appendicular skeleton - blue
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D. Long bone structure
1. gross anatomy
a. diaphysis
*shaft
*makes up most of bone’s length
*composed of compact bone
b. periosteum
*protective membrane-covering of
diaphysis
c. Sharpey’s fibers
*also called perforating fibers
*c.t. fibers that secure periosteum
to bone
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d. epiphyses
*ends of long bones
*area of spongy bone enclosed in
thin layer of compact bone
e. articular cartilage
*covers external surface of epiphyses
*glassy hyaline cartilage
*provides a smooth, slippery surface
to reduce friction @ joints
f. epiphyseal plate
*flat plate of hyaline cartilage
*seen in young, growing bone
*causes lengthwise growth of a long
bone
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g. medullary cavity
*also called the yellow marrow cav.
*cavity of the shaft
*adultsstorage area for adipose
tissue
*infantscontains red marrow &
forms blood cells
(adults: red marrow is found only
in spongy bone cavities of flat
bones & epiphyses)
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Epiphysis – dark green
Epiphyseal line – light green
Diaphysis – brown
Articular cartilage – purple
Periosteum – blue
Spongy bone/red marrow – red
Compact bone – pink
Medullary cavity/yellow marrow – yellow
Nutrient artery - orange
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2. microscopic anatomy
a. osteocytes
*mature bone cells
b. lacunae
*tiny cavities w/i matrix
*contain osteocytes
c. lamella
*concentric circles in wh/ lacunae
are arranged
d. Haversian canals
*central canals around wh/ the
lamella form
NOTE: see page 92 for micrograph of the structure of
bone
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e. osteon
*also called Haversian system
*each complex consisting of a
central canal + matrix rings
*canals run lengthwise carrying
blood vessels & nerves to all
areas of bone
f. canaliculi
*transportation system
*connect bone cells to nutrient
supply
*radiate o/w from the central canals
to all lacunae
*reason bone cells are well nourished
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3. bone markings (pg.134)
a. fossa
*shallow, basinlike depression in a
bone
*may serve as an articular surface
b. fissure
*narrow, slit-like opening
c. foramen
*round/oval opening through a bone
*for blood vessels &/ nerves
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Fossa
Fissure
Foramen
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E. Bone formation, growth, remodeling
1. formation & growth
a. ossification
*process of bone formation
*2 phases
-osteoblasts (bone forming
cells) cover hyaline cartilage
-hyaline cartilage is digested
away forming medullary
cavity
b. appositional growth
*increase in diameter of bone
c. osteoclasts
*bone-destroying cells
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2. bone remodeling
a. nec. for bones to retain normal prop. &
strength as body increases in size &
strength
b. PTH (parathyroid hormone)
*determines when bone is to be
broken down(body needs
calcium)/formed (has to much Ca)
*stresses (muscle pull, gravity)
determine where bone matrix is to
be broken down/formed
c. allows skeleton to remain as strong &
vital as possible during growth, injury,
etc.
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F. Problems
1. Rickets
a. childhood disease in wh/bones fail to
calcify
b. bones soften  bowing of legs
c. usu. due to lack of Ca or lack of Vit. D
wh/ is needed to absorb Ca into
bloodstream
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2. Fractures (bone breaks)
a.simple (closed)
*bone breaks cleanly
*does NOT penetrate the skin
b. compound (open)
*bone ends penetrate through the
skin
Simple fracture
Compound fracture
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comminuted
c. comminuted fracture
*bone breaks i/t many fragments
*common in elderly (bones are
more brittle)
d. compression fracture
*bone is crushed
*common in porous bones
e. greenstick
compression
*incomplete break
*common in children (flexible bones)
Greenstick ----------
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3. fracture repair (pg. 138)
4 mj. Events:
a.hematoma forms
blood-filled swelling
b. break is splintered by a fibrocartilage
callus
c. bony callus is formed
fibrocartilage is gradually
replaced by spongy bone
d. bone remodeling occurs
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