Dysfunction of the Skeletal
System
Homeostatic Imbalances and
Bone Repair
Homeostatic Imbalances of Bone
•
•
•
•
Osteoporosis
Arthritis
Osteomalacia/Rickets
Paget’s Disease
Homeostatic Imbalances of Bone
(Osteoporosis)
• Normal matrix, but decreased bone mass
– Bone reabsorption > Bone deposit
– Osteoclast more active than osteoblasts
• Porous, light, fragile bones
• Spongy bone most vulnerable
Ex. Compression fractures of vertebrae, neck of
femur
Homeostatic Imbalances of Bone
(Osteoporosis)
• Bone health maintained by hormones
– Estrogen: restrain osteoclasts and promote bone
deposition
• Greatest Risk Factors:
–
–
–
–
–
–
–
Older, post-menopausal women
Petite body
Insufficient load-bearing exercise
Diet poor in Calcium, Vit D and protein
Thyroid disease
Diabetes
Smoking (reduces estrogen, promotes weight loss)
Homeostatic Imbalances of Bone
(Osteoporosis)
• Prevention: focuses on reversing risk factors
– dietary supplements
* Associated risk of heart attack,
stroke, breast and uterine cancer
– Load bearing exercise
– * hormone (estrogen) replacement therapy (HRT)
• Alternative Therapies:
– Alendronate: drug reduces osteoclast activity
– Selective Estrogen Receptor Modulators (SERMS): mimic
estrogen’s benefits without risks associated w/ HRT
– Statins: cholesterol medication that increases bone density
as side effect.
– Soy protein: supplements diet, contain estrogen-like
compounds
Homeostatic Imbalances of Bone
(Osteoporosis)
• Bone Density Test
•Special X-rays used
to measure mineral
content of bone.
•Repeated every 2–3
years
Bone Density Scan of a NORMAL menopausal woman
Color Ranges: Blue/purple, least dense to white, most dense
Homeostatic Imbalances of Bone
(Arthritis)
•
•
•
•
> 100 types
inflammation of joint, causing pain
Often cartilage is broken down
Rheumatoid arthritis
– autoimmune
– body’s own cells of IS attack soft tissue around
joint.
Homeostatic Imbalances of Bone
(Osteomalacia/Rickets)
• “Soft bones”:
– bones w/ matrix and structure, but minimal calcium
– Insufficient Ca and Vit D diet
• Osteomalacia: adult form
– Reversible with dietary changes.
• Rickets: youth form
– more severe: bones still developing
– causes bowed legs and deformed pelvis, skull, ribs
– Abnormally long bones due to lack of calcification of
epiphyseal plate
– Bone deformities permanent.
Homeostatic Imbalances of Bone
(Paget’s Disease)
• Disorganized resorption and formation of bone
• High spongy bone: compact bone ratio
• Reduced mineralization
• Osteoclast activity <
Osteoblast activity causing
bone thickening
Fractured right femur of
Paget’s patient due to
weakening of bones
Classification of Fractures
I. Position
•Non-displaced: bone
ends in alignment
•Displaced: bone ends
out of alignment
Classification of Fractures
II. Breakage
•Complete: Fractures break all
the way through
•Incomplete: partial fracture
Classification of Fractures
III. Orientation
• Linear: fracture runs parallel along the axis
• Transverse: fracture is perpendicular to
the axis
Linear
Transverse
Classification of Fractures
IV. Skin Penetration
Simple:
Fracture does
not pierce
skin
Compound:
Fracture pierces
skin
Classification of Fractures
Appearance
• Comminuted: Bone fragments into multiple
pieces
• Compression: crushed bone
Classification of Fractures
Appearance
• Spiral: ragged break due to twisting forces
•Depressed: Bone portion
pushed inwards
Classification of Fractures
Appearance
• Greenstick:
incomplete
fracture; Only one
side of the shaft
breaks; the other
side bends.
Classification of Fractures
Position
• Epiphyseal:
separation of
epiphysis from
diaphysis along
epiphyseal plate
Treating Fractures
1. Reduction: realignment of
broken bone ends
– Closed/External: hands used to
coax bones back to realignment
– Open/Internal: surgical
realignment of bone ends
secured together by pins or
wires
2. Immobilization with cast or
traction
Bone Repair
•Osteoblasts convert
cartilage to spongy
bone
•Blood clots
•Capillary growth
•Bone cell death
•Phagocytes eat cell debris
•inflammation
•Fibroblasts bridges gap with collagen FIBER
•Chondroblasts secrete CARTILAGE matrix to create framework
for bone formation. Cartilage later calcifies and dies.
Bone Lengthening Surgery
• Lengthens bone up to 3 in
• Procedure:
– Breaking bones of leg (tibia/fibula or femur)
– Bone moved apart 1 mm/day w/ external device
– Body regenerates new
bone to fill-in space as
matrix tears
• Repair deformities
• Cosmetic Reasons
– (Extreme make-over)
Bound Feet in China
• Small “lotus” feet
(< 4 in.) = symbol
of beauty in China
up until 1920’s
• Young girls’ feet
broken and bent
so toes bound
under foot