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Bones are classified according to shape
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Long bones
Short bones
Flat bones
Irregular bones
Sesamoid bones (round)
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Long bones – longer than they are wide.
They consist of a long shaft with two bulky
ends.
Examples: Thigh, leg, arm, and forearm
bones.
The walls of the shaft of a long bone are
made of compact bone and the ends
(epiphyses) are made of spongy bone.
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Diaphysis – shaft of long
bone.
Medullary cavity – hollow
space – A thin layer of cells
called the endosteum lines
the cavity, and marrow fills
it.
Epiphysis – At the end of
the diaphysis.
End of the epiphysis is
covered by cartilage which
allows smooth movement
against other bones.
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Epiphyseal plate – in
growing bones – it is a
plate of hyaline cartilage
between the epiphysis and
diaphysis. This is where
growth takes place.
It is gradually replaced by
bone tissue. Growth stops
when the bone has
completely taken the place
of cartilage.
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Periosteum – a tough,
fibrous connective tissue
that covers long bones.
Periosteum has many
nerves, blood vessels and
osteoblasts (cells that
create new bone)
Nutrient foramina are
small openings through
which blood vessels enter
into the bone.
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Roughly cube-shaped
Primarily made of spongy bone, covered by a
thin layer of compact bone.
Bones of the wrist and ankle
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Thin, flattened, and often curved.
Usually arranged like a sandwich. They have
a middle layer of spongy bone, covered on
each side by a later of compact bone.
Examples: bones of the skull
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Don’t fit in any of the other categories.
Primarily spongy bone, covered with a thin
layer of compact bone.
Examples: vertebrae and some skull bones.
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Small and nodular
bones.
Usually embedded
within a tendon
adjacent to a joint
Example: patella and
sesamoid bones of foot
General bone structure
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2 types of bone
a) compact
b) spongy (cancellous)
These 2 types differ in
how tightly tissue is
packed together.
Compact bone
Spongy bone
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Bone cells are called osteocytes
The Haversian system – consists of a central
canal surrounded by lamellae (rings) of
matrix. Between the rings the osteocytes are
located in spaces called lacunae.
Small channels called canaliculi radiate from
the lacunae to the Haversian canal and
connect the osteocytes.
This cylindrical shaped unit is called an
osteon.
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Composed of
osteocytes and
extracellular matrix.
Bone cells here do not
surround a central
canal.
Cells lie within the
trabeculae (bony
spaces) and get
nutrients through
diffusion
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Osteogenesis/ossification – either term is
used to indicate the process of bone
formation.
Parts of the skeleton form in the first few
weeks after conception. Bone development
continues throughout adulthood.
Bone development may continue for repair of
fractures or to remodel bone to meet
changing lifestyles.
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Osteoblasts – bone forming cells
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Osteocytes – mature bone cells
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Osteoclasts – break down and reabsorb bone.
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The replacement of sheet-like connective
tissue membranes with bony tissue.
Bones formed in this way are called
intramembranous bones.
Examples: Flat bones of the skull, and some
irregular bones.
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Endochondral ossification – replacement of
hyaline cartilage with bony tissues.
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Most bones of the skeleton formed this way.
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Bones called endochondral bones.
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Long bones continue to grow (lengthen) while
the cartilaginous cells of the epiphyseal
plates are active.
Once the ossification centers meet and the
epiphyseal plates ossify – no further growth
occurs.
An injury to an epiphyseal plate may cause
uneven growth. For this reason injuries to
the epiphysis are treated very carefully.
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Throughout life, osteoclasts resorb bone
matrix, and osteoblasts replace it.
Hormones that regulate bone calcium control
these opposing processes.
So in an adult, total bone mass stays about
the same throughout life.
Vitamin D, calcium, and physical exercise are
necessary for bone development, growth, and
repair.
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Support – a rigid framework
Protection – of the soft body parts.
Movement – Sites for muscle attachment. Bones
and muscles work as a lever system.
Storage – Intercellular matrix of bone contains
calcium salts. Bone also contains sodium,
magnesium, potassium, and stores fat.
Blood cell formation – takes place mostly in bone
marrow. This process is called hematopoiesis.
Red marrow helps form RBCs, WBCs, & platelets.
Yellow marrow stores fat.
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206 named bones
Other bones:
◦ Wormian bones – small
bones in the joints
between certain cranial
bones.
◦ Sesamoid bones – small
bones that grow in
certain tendons.
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Axial skeleton – 80
bones
◦ Head, vertebral column,
ribs, sternum, and hyoid
Appendicular skeleton –
126 bones
Upper and lower limbs,
and their attachments
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Anterior skull
Skull – 28 bones
Bones in the skull
are tightly
interlocked along
irregular lines
called sutures.
Some skull bones
contains sinuses –
air filled cavities
lined with mucous
membranes.
Numerous
openings or
foramina to allow
blood vessels and
nerves to enter.
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Cranium – 8 bones
interlocked to enclose
the brain.
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Lateral view of skull
Frontal
Parietal bones (2)
Occipital bone
Temporal bones (2)
Sphenoid
Ethmoid
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Frontal bone
◦ Anterior portion of the
skull above the eyes, part
of the nose, and the
upper eye socket
◦ Supraorbital foramen or
notch – blood vessels and
nerves pass to forehead.
◦ Frontal sinuses – above
the eyes – cavity.
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Parietal bones – 2 of
them.
Joined to each other in
the midline by the
sagittal suture and to
the frontal bone by the
coronal suture
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Occipital bone
◦ Most of the dorsal part of
the skull.
◦ Lambdoid suture joined to
the parietal bones.
◦ Foramen magnum is the
large opening on the lower
surface of the occipital
bone- spinal cord passes
through foramen magnum
Foramen magnum in the occipital
bone
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Temporal bones – the
sides and base of the
cranium
◦ External auditory meatus
– opening to the middle
ear.
◦ Mastoid process – a knob
that contains air cells
◦ Styloid process
◦ Zygomatic process
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Sphenoid – crosses the
cranial floor
Forms the sides of the
skull and base of the
cranium
The pituitary gland sits
in the sella turcica, a
part of the sphenoid
bone.
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Ethmoid bone – forms
most of the bony area
between the nasal
cavity and orbits.
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Skull of newborns not
completely joined
together.
There are areas called
fontanels or soft spots.
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14 bones
13 are interlocked
1 movable mandible – the lower jawbone
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Maxillary
Palatine
Nasal
Lacrimal
Zygomatic
Inferior Nasal conchae
Vomer
Mandible
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Maxillary bones form
the upper jaw.
Hard palate – roof of
the mouth is the
palatine process
Has a large maxillary
sinus
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Behind the maxillae
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Bones are roughly L shaped
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Form the hard palate and side walls of the
nasal cavity.
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Nasal bones
Small rectangular
bones that form the
bridge of the nose.
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Located in the medial
wall of the orbits.
Each one has a lacrimal
groove – the pathway
for a tube that carries
tears from the eyes to
the nasal cavity.
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Form the prominences
of the cheeks
(cheekbones)
Temporal processes
form the zygomatic
arch.
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Thin curved bones
attached to the lateral
walls of the nasal
cavity.
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The inferior part of the
midline in the nasal
cavity.
Part of it forms the
nasal septum.
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The lower jaw
Horseshoe shaped
body that forms the
chin.
The ramus projects
upward at each end.
Forms the
temporomandibular
joint.
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3 tiny bones
Malleus – hammer
Incus – anvil
Stapes – stirrup
Transmit sound from
the eardrum to the
inner ear.
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Not part of the skull
U shaped bone in the
neck.
It is unique because it
is the ONLY bone in
the body that does not
articulate with another
bone.
Anchored by ligaments
to the temporal bone.
Base for the tongue
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Part of the axial skeleton
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Extends from skull to pelvis.
Contains 26 bones called vertebrae.
Separated by pads of fibrocartilage called
intervertebral disks.
Disks act as shock absorbers
Four curvatures that increase strength and
resilience of the column.
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Thoracic curvature
Sacral curvature
Cervical curvature
Lumbar curvature
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All vertebrae have
common structure
Foramen – opening for
the spinal cord
Spinous process – what
protrudes near the skin
of the back
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7 cervical vertebrae – designated C1 through
C7.
Have transverse foramina in the transverse
processes.
Spinous processes are forked.
Atlas – another name for C1
Axis – another name for C2
Atlas and axis pivot to rotate the neck.
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12 thoracic vertebrae,
designated T1-T12.
They have facets to
articulate with the ribs.
Long pointed spinous
processes.
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5 lumbar vertebrae,
designated L1-L5
Large heavy bodies to
support body weight.
Many back muscles
attached.
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Sacrum – triangle
shaped bone below
lumbar vertebrae.
Coccyx – tailbone.
Some muscles attach
to coccyx.
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Protects the heart, lungs and large vessels.
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Supports the bones of the shoulder
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Thoracic vertebrae, ribs, and sternum
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Also called the
breastbone
3 parts
◦ Manubrium – upper
triangle part
◦ Body – middle slender
part
◦ Xiphoid process – very
small end.
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12 pairs- each attached
to thoracic vertebra
Upper 7 pairs are true
ribs – they attach to
sternum
Lower 5 pairs – false ribs
– cartilage does not
reach sternum.
Of the lower 5 pairs, the
last 2 pairs are called
“floating”
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126 bones
This part of the skeleton is designed for
movement.
The two girdles (pelvic and pectoral) are
attached to the abdomen.
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Each half consists of 2
bones:
◦ The clavicle (collar bone)
◦ Scapula (shoulder blade)
◦ Scapula has numerous
muscles that attach.
◦ The acromion process
articulates with the
clavicle
Scapula
Broken Clavicle
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Humerus – single long
bone of the upper arm.
Head of the humerus
fits into the scapula.
The tuberosities and
epicondyles are places
where muscles attach.
The olecranon fossa –
where the ulna fits to
form the elbow.
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2 bones radius and
ulna
When the forearm
rotates, the radius
crosses over the ulna
Radius has a disc-like
head which articulates
with the humerus.
Ulnar head articulates
with the wrist.
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8 bones in the wrist –
tightly bound by
ligaments – called
carpals.
5 metacarpals in the
hand (numbered 1-5
starting at the thumb)
Phalanges – 14 bones
of the fingers. 3 bones
in each finger, 2 in
each thumb
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Attaches the lower extremities to the axial
skeleton.
Provides support for the weight of the body.
Consists of 2 coxal bones (hip bones)
In childhood, each coxal bone has 3 separate
parts – ilium, ischium, and pubis.
In an adult, these are fused to form a single
bone.
The acetabulum on each side is a depression
where the femur articulates
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Acetabulum – where
the femur articulates
with the pelvis.
Greater sciatic notch is
where the sciatic nerve
passes through and
down the leg.
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This is the important
passage in childbirth.
This large opening is
called the pelvic outlet.
True pelvis
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Bones of the thigh,
lower leg, ankle, and
foot.
Support entire weight
of the body when we
are upright.
Bones are larger and
stronger than upper
extremity.
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One single long bone –
the femur.
Largest, longest, and
strongest bone in
body.
Top of the femur is
called the femoral
head.
Muscles attach at the
trochanters.
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Tibia is the weightbearing bone.
Tibia articulates with
the femur to form the
knee joint.
Lateral and medial
malleoli form the ankle
joint (these are the
bumps you feel on
your ankle)
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Anterior crest of the
tibia is what forms
your shinbone.
Head of the fibula is at
the proximal portion of
the bone.
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Foot is composed of
the ankle, instep and 5
toes.
There are 7 tarsal
bones in the ankle.
The largest one is the
heel or calcaneus.
The 5 metatarsals
make up the instep.
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Phalanges – the 14 toe
bones.
Three phalanges in
each toe except the big
toe where there are
only 2.
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The patella is enclosed
within the patellar
tendon.
It provides a smooth
surface for the tendon.
It protects the knee
joint from the front
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Another name for joint – where 2 bones come
together.
3 types
◦ Fibrous
◦ Cartilaginous
◦ Synovial
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Immovable joints are
called fibrous joints.
The bones are in very
close contact,
separated only by a
thin layer of fibrous
connective tissue.
Sutures of the skull are
an example
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Bones are connected
by hyaline or
fibrocartiliage.
Examples: ribs and
sternum.
These types separate
the vertebrae
Symphysis pubis
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Most joints in the
body.
Freely movable
Ends of opposing
bones are covered with
hyaline cartilage and
are separated by a
space called the joint
cavity.
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The joint capsule
encloses the bones.
The inner layer of this
capsule is the synovial
membrane.
Some synovial joints have
pads of fibrocartilage
called menisci.
These joints may also
have fluid-filled sacs
called bursae.
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Are classified by the types of movement they
allow
◦ Ball and socket – oval or round head that articulates
within a cup-shaped cavity. Examples: hip, shoulder
◦ Ellipsoidal – oval shaped condyle fits into elliptical
shaped cavity – Examples: btw. Metacarpals and
phalanges
◦ Gliding joints – nearly flat. Examples: joints within the
wrist and ankle
◦ Hinge – Movement in 1 plane only: Examples: elbow,
knee
◦ Pivot – rotation – Example: joint btw first vertebra and
skull
◦ Saddle: Both concave and convex. Example: joint
between carpal and metacarpal bones of thumb
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Trauma
Metabolic
Endocrine
Infections
Inflammatory
Nutritional
Malignant tumors (cancer)
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Fractures
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Dislocations and subluxations
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Sprains and strains
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Severe injuries (amputations, etc)
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A fracture is any break in the continuity of
bone.
Most commonly caused by trauma.
BUT, aging and metabolic disease may
weaken bones so that they break easily.
Children’s bones tend to heal more quickly
than adults.
Greenstick fracture
Spiral fracture
Comminuted fracture
Transverse fracture
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Closed reduction – moving fractured pieces
back into place by physical manipulation.
Open reduction – Using surgical techniques
to move fractured pieces into place. This
may include the use of hardware either
internally (internal fixation) or externally
(external fixation)
Internal fixation
External fixation
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Bone healing is a slow process. Tissue is
usually destroyed during the injury, and bone
cells reproduce slowly.
The first stage of fracture healing is the
formation of a fracture hematoma (a blood
clot at the fracture site). This plugs the gap
between the broken ends of bones)
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Second step in healing – capillaries grow into
the hematoma. Phagocytic cells come to the
area to clean up dead tissue. This process
may take several weeks.
This organization is called a procallus.
Third step – fibrocartilage tissue forms at the
site of the fracture. This also lasts about 3
weeks.
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Bony callus forms next – it is usually made of
spongy bone. This callus lasts for 3-4
months before the bones remodel.
Remodeling is the final step in repair.
Osteoblasts lay down new compact bone and
osteoclasts reabsorb spongy bone.
Once healing is complete, full bone strength
is restored.
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A subluxation is a
partial dislocation
Dislocations – 1 bone
has slipped out of
joint.
Finger dislocation
Normal ankle anatomy
Ankle sprain
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Gout is a disease
caused by
accumulation of uric
acid crystals within the
joint.
The most commonly
affected joint is the
great toe.
Treated with
medications and diet
change.
gout
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Osteoporosis is a
result of calcium loss
from bones.
It occurs in both men
and women, but
usually starts earlier
and is more severe in
women.
Estrogen decrease
plays a role.
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Osteomyelitis – is the
clinical term for an
infection in the bone
itself.
This can be very severe
and result in loss of a
limb.
Left x ray is normal
Right x-ray is infected
tibia
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Includes
◦ Tendinitis
◦ Bursitis
◦ Arthritis (either
Rheumatoid or
Osteoarthritis)
Achilles tendinitis
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A bursa is a fluid filled
sac that acts as a
cushion.
It usually is located
between tendons and
ligaments.
Normal olecranon bursa
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There are 2 types of
arthritis:
Osteoarthritis – the
wearing out of joint
cartilage due to aging
and or overuse
Rheumatoid arthritis –
the inflammation of
joints due to an
autoimmune response.
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Rickets is a deficiency
in vitamin D.
Not common in the US
at this time.
More common in third
world countries.
Causes the bones to
bow – legs will not be
able to support weight.
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The most common type of primary bone
tumor is osteosarcoma.
It can be a disease of any age.
Other tumors (lung, breast, or other cancers)
may metastasize (spread) to the bone as well.
Symptoms may not be present until the bone
breaks.
Osteosarcoma
Malignant hand tumor