(i) atrophy

(ii) dystrophy

Name two causes for muscle atrophy.

• disuse - muscle fibers become reduced and lose their ability to contract.
• Chronic illness .

Describe muscular dystrophy.

• Occurs when voluntary muscle becomes progressively weak.
• The muscle cell undergoes necrosis.
• The muscle fibers are replaced by fat and connective tissue.
• The deposition of fat and connective tissue leads to a displacement of muscle cells.
• Fibrosis sets in.

The description below depicts what type of muscular dystrophy

• occurs in boys in early childhood; becomes evident at 2-3 years of age;
• is a genetic recessive disorder
• gene producing dystrophin is located on X-chromosome
• muscle fibers that do not have dystrophin lack interaction between sarcolemma and extracellular matrix
• fat and connective tissue are deposited in muscle.

dystrophin

In Duchenne muscular dystrophy, muscle fibers that do not have dystrophin lack interaction between ____ and ______ matrix

sarcolemma

extracellular

• early development of motor difficulties
• inability to walk
• symmetric weakness of arms
• enlargement of calf muscles, buttocks, thighs
• characteristically, disorder begins with lower extremity weakness and progresses upwards, finally affecting head and chest
• calf muscles pseudohypertrophy (enlarge but become weaker) and muscles become infiltrated with fat

The characteristics below are those of what type of dystrophy? 

• occurs later in childhood, between 5 and 15 years of age
• milder in clinical features
• muscles become weak
• become wheel chair bound

In Becker's muscular dystrophy, it develops between what ages?