Skeletal System
Microanatomy
Functions
of Bones
Support
Protection
Movement
Storage
– fat, minerals
Blood cell formation
(hematopoiesis)
Compact Bone – dense, smooth,
homogeneous
Spongy Bone – small, needle-like pieces
with lots of open space
Long
bones –
longer than
wide, shaft with
heads at both
ends, mostly
compact,
Ex.
femur,
humerus
Short
bones – cube shaped,
mostly spongy,
Ex.
bones of wrist and ankle
Flat
bones – thin, flat, curved,
compact bones sandwiching
spongy
Ex. bones of skull, ribs,
sternum
Irregular
bones –
don’t fit other
categories
Ex. vertebrae, hip
 Diaphysis
– shaft,
composed of
compact bone
 Periosteum
–
membrane of
connective tissue that
covers diaphysis
 Sharpey’s
fibers –
connective tissue
fibers that connects
periosteum to
diaphysis
Epiphyses
– ends of the bone, thin
layer of compact enclosing an area
filled with spongy
Articular
cartilage – covers epiphysis,
decreases friction between bones
Epiphyseal
Plate – growth plate, line
of cartilage, (adults have epiphyseal
line)
Cavity
– inside the diaphysis
Adults
– yellow marrow (medullary)
cavity – stores adipose, red marrow
confined to spongy bone of epiphysis
and flat bones
Children
cells
– red marrow – forms blood
Projections/processes
Muscle
and ligament attachment –
tuberosity, crest,
Form
joints – head, facet
Depressions/cavities
– allow blood
vessels and nerves to pass
Fossa,
sinus, groove, fissure,
foramen
Osteocytes – mature bone cells
Lacunae
– tiny cavities arranged in
circles called lamellae
Haversian
canals – center of lamellae,
run lengthwise through bone, carrying
blood vessels and nerves
Osteon
– complex of the above,
many/bone
Canaliculi
– radiate outward to connect
all bone cells to the nutrient supply
Volkmann’s
canals – run at right angle
to the shaft to connect interior and
outside areas of the bone
Ossification
In
– formation of bone
fetus, skeleton composed of
cartilage, but it is replaced by bone
during development (uses cartilage as
model)
Osteoblasts
– bone-forming cells –
covers cartilage with a matrix of bone
Once
enclosed, cartilage is digested
away, leaving medullary cavity
By
birth, most cartilage has been
replaced by bone except articular
cartilage and epiphyseal plates
Appositional
growth – bone widens –
add bone tissue to the external face
and osteoclasts remove bone from
inner surface
Controlled
by growth hormones
and sex hormones (during
puberty)
Bone
remodeling
Necessary
in response to calcium
levels in the blood and the pull of
gravity
Simple
fracture – bone does not
break the skin (closed)
Compound
fracture – bone breaks
through skin (open)
Comminuted – many fragments
Compression – crushed
Depressed – pressed inwards (typical in
skull)
Impacted – ends forced into each other
(ex. break a fall)
Spiral – ragged break from twisting
(sports, child abuse)
Greenstick –
incomplete
(more
common in
children)
reduction – realignment of bone
Hematoma
Break
forms
splintered by fibrocartilage
callus – a mass of repair tissue, acts
to close gaps
Bony
callus forms – osteoblasts and
osteoclasts migrate and work to replace
fibrocartilage callus with spongy bone
Bone
remodeling