Skeletal and Muscular Systems

• Myth No. 1: A fracture is a milder form of bone injury than a broken bone.

• Myth No. 2: Once bones are fully developed, they stop changing.

• Myth No. 3: Osteoporosis is a painful bone condition.

• Myth No. 4: Vitamin D deficiency causes rickets, a disease of malnourished children.

• Myth No. 5: If you have broken a bone, you'll know it right away.

• Myth No. 6: A broken bone heals stronger than it was before the break.

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Bone myths

Skeletal System

• The framework for your body • 206 bones • “Os-” bone; • “Osteo-” bone • Two divisions

–Axial: Skull, vertebrae, ribs, sternum –Appendicular; arms and legs.

• Contains both bone tissue and cartilage

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Osteocytes are bone cells

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Bone contains:• Minerals – especially calcium which

provides for the hardness of bone • Collagen fibers which provides

strength of bone • If one or the other is missing bones

will be soft or brittle

Bone has an excellent blood supply

Joint• “art-” and “arthr-” mean joint • Ligaments stabilize joints • Cartilage caps the bones at the joint

for a smooth surface

Cartilage

• “chondr-” means cartilage • Healing capability is poorer than

bone • Mostly due to decreased blood

supply.

Skeleton Function

• Framework; muscles attach • Support; allows upright posture • Movement; muscle leverage • Protection; Brain, lungs, heart, etc. • Blood cell production from bone

marrow; red and white blood cells • Storage of minerals & fat; calcium,

phosphate. • Fat in yellow marrow.

Disorders of Skeleton-Osteoporosis

Incidence• Common in the U.S. • Responsible for many

fractures each year • Affect 200 million

women worldwide - 10% aged 60; 66% women aged 90

• Men; 27% for over 50

Cause• Inadequate calcium • Females, older more

commonly • Sedentary lifestyle • Poor diet • Pregnancy giving

calcium to fetus • Menopause leads to

calcium withdrawal from bone

Prevention/Treatment

• Weight-bearing exercise • Calcium in diet • Estrogen replacement

therapy after menopause

• Drugs, such as Fosamax

Arthritis

• Osteoarthritis is the wear and tear arthritis due to joint damage and injuries

Arthritis• Rheumatoid arthritis is an

autoimmune disease in which the immune system attacks the joints in the body leading to their gradual destruction

Sprain• Joint injury that stretches or tears

supportive ligaments • A severe sprain can result in a

dislocation

Fracture• Generally bones heal well with

proper alignment, stabilization, and without infection

Fractures• Hairline or greenstick: young, soft bone in

which the bone bends and partially breaks • Simple • Compound = Open; skin is broken • Comminuted: bone has broken into a

number of pieces.

Muscular System

• “Myo-” means muscle

• Muscle tissue is capable of contraction

Smooth muscle

• Found in the wall of tubular structures such as intestine

•Involuntary • Smooth appearance microscopically • Peristalsis is a wave like contraction

of smooth muscle

Cardiac Muscle

• Heart muscle •Involuntary • Striated, or striped when observed

microscopically

Skeletal Muscle

• Muscle attached to the skeleton • Voluntary • Striated microscopically

Skeletal Muscle• Tendons attach muscle to bone

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Microscopic Muscle• Myofiber =

muscle cell • Myofibril =

the striated parts of the muscle cell

• Myofilaments = the proteins that make up the myofibrils

Myofilaments

• The two main proteins that comprise the myofilaments are: –Myosin – very thick protein –Actin – very thin protein

Sarcomere• The actin and myosin in the muscle

cells are arranged in small groups called SARCOMERES

• Since contraction occurs at the microscopic level of the sarcomere, the sarcomere is the functional unit of contraction

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Sliding Filament Theory

• This describes the mechanics of muscle contraction

• The myosin “heads” grab on to the actin protein and pull the actin towards the center of the sarcomere, making the sarcomere shorter.

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ATP

• ATP is necessary for muscle contraction

• Running out of ATP may lead to muscle fatigue

Motor Neuron

• Skeletal muscle will not contract unless a motor neuron (movement nerve cell) stimulates it to contract

Motor Unit

• A motor neuron plus how every many skeletal muscle cells it serves is a motor unit

• A motor unit that has one neuron to one muscle cell allows for very precise movements

• A motor unit that has one neuron to 400 muscle cells does not provide precise control