Select the correct statement with respect to disorders of muscles in humans.

Options

A. Failure of neuromuscular transmission in inyasthenia gravis can prevent normal swallowing
B. Accumulation of urea and creatine in the joints causes their inflammation.
C. An overdose of vitamin D causes osteoporosis.
D. Rapid contractions of skeletal muscles cause muscle dystrophy.

Answer

To solve the question regarding the correct statement about disorders of muscles in humans, we will analyze each statement provided and determine which one is accurate.

### Step-by-Step Solution:

1. **Understand Myasthenia Gravis**:
- Myasthenia gravis is an autoimmune disorder where autoantibodies bind to the acetylcholine receptors at the neuromuscular junction.
- This binding impairs the ability of acetylcholine to induce muscle contraction, leading to muscle weakness and fatigue.

2. **Evaluate the First Statement**:
- The first statement claims that "failure of neuromuscular transmission in myasthenia gravis can prevent normal swallowing."
- This is true because the weakness of muscles involved in swallowing can indeed occur due to impaired neuromuscular transmission.

3. **Analyze the Second Statement**:
- The second statement suggests that "accumulation of urea and creatine in the joint causes their inflammation."
- While this is true for gouty arthritis (which involves uric acid), it does not pertain to muscle disorders, making this statement incorrect in the context of muscle disorders.

4. **Examine the Third Statement**:
- The third statement states that "an overdose of vitamin D causes osteoporosis."
- Osteoporosis is primarily a bone disorder, not a muscle disorder, so this statement is also incorrect in the context of muscle disorders.

5. **Review the Fourth Statement**:
- The fourth statement mentions that "rapid contraction of skeletal muscle causes muscular dystrophy."
- Muscular dystrophy is a genetic disorder characterized by muscle degeneration and weakness, but it is not caused by rapid contraction. Therefore, this statement is also incorrect.

6. **Conclusion**:
- After evaluating all the statements, the first statement regarding myasthenia gravis is the only correct statement concerning muscle disorders in humans.

### Final Answer:
The correct statement with respect to disorders of muscles in humans is:
**"Failure of neuromuscular transmission in myasthenia gravis can prevent normal swallowing."**

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