State and explain the disorders related to muscles.

i. Muscular dystrophy: 

1. It is a gradual wasting disease affecting various groups of muscles. 

2. It is a genetic disorder. 

3. Usually the voluntary skeletal muscles are weakened whereas internal muscles such as diaphragm are not affected in the patient suffering from this disorder. 

4. The Duchenne type of muscular dystrophy usually occurs in boys, affecting their lower limbs. 

5. Limb girdle muscular dystrophy affects the muscles of shoulders or hips and it usually starts in adults between 20 – 30 years. 

6. There is no cure for this disease. 

ii. Myasthenia gravis:

1. It is a weakness of skeletal muscles. 

2. It is caused by an abnormality at the neuromuscular junction that partially blocks muscle contraction. 

3. It is an autoimmune disorder caused by excessive production of certain antibodies in the blood stream. These antibodies bind to acetylcholine receptors of neuromuscular junction. Thus, the transmission of nerve impulses to the muscle fibres is blocked. This causes progressive and extensive muscle weakness. 

4. It may affect the eye and eyelid movements, facial expression and swallowing. 

5. The degree of muscle weakness varies from local to general. 

6. Symptoms: Ptosis (drooping or falling of upper eye lid), diplopia or double vision, difficulty in swallowing, chewing and speech.