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 vulnerableEx. Compression fractures of vertebrae, neck of

femur

• 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)

Homeostatic Imbalances of Bone(Osteoporosis)

• Prevention: focuses on reversing risk factors– dietary supplements– 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

* Associated risk of heart attack, stroke, breast and uterine cancer

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 FracturesI. Position

•Displaced: bone ends out of alignment

•Non-displaced: bone ends in alignment

Classification of FracturesII. Breakage

•Complete: Fractures break all the way through

•Incomplete: partial fracture

Classification of FracturesIII. Orientation

• Linear: fracture runs parallel along the axis

• Transverse: fracture is perpendicular to the axis

Linear Transverse

Classification of FracturesIV. Skin Penetration

Simple:

Fracture does not pierce skin

Compound:

Fracture pierces skin

Classification of FracturesAppearance

• Comminuted: Bone fragments into multiple pieces

• Compression: crushed bone

Classification of FracturesAppearance

• Spiral: ragged break due to twisting forces

•Depressed: Bone portion pushed inwards

Classification of FracturesAppearance

• Greenstick: incomplete fracture; Only one side of the shaft breaks; the other side bends.

Classification of FracturesPosition

• 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

•Blood clots

•Bone cell death

•inflammation

•Osteoblasts convert cartilage to spongy bone

•Capillary growth

•Phagocytes eat cell debris

•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