Skeletal and Muscular Systems

Skeletal System

• The framework for your body

• 206 bones

• “Os-” bone;

• “Osteo-” bone

Osteocytes are bone cells

Bone contains:

• Minerals – especially calcium which provides for the hardness of bone

• Collagen fibers which provides strength of bone

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

Skeleton Function

• Framework

• Support

• Movement

• Protection

• Blood cell production from bone marrow

• Storage of minerals & fat

Disorders of Skeleton-Osteoporosis

Incidence

• Common in the U.S.

• Responsible for many fractures each year

Cause

• Inadequate calcium

• Females, older more commonly

• Sedentary lifestyle

• Poor diet

• Pregnancy giving calcium to fetus

• Menopause lead to calcium withdrawal from bone

Prevention/Treatment

• Weight-bearing exercise

• Calcium in diet

• Estrogen replacement therapy after menopause

• Drugs, such as Fosamax

Arthritis

• Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the joints in the body leading to their gradual destruction

Arthritis

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

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

• Simple

• Compound = Open

• Comminuted

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

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

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 leads 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