Which cranial nerve is the longest and supplies all parts of body other than head :

Options

A. Trochlear nerve
B. Vagus nerve
C. Occulomotor nerve
D. Auditary nerve

Answer

To determine which cranial nerve is the longest and supplies all parts of the body other than the head, we can analyze the options provided step by step.

### Step 1: Identify the Options
The options given are:
1. Trochlear nerve
2. Vagus nerve
3. Oculomotor nerve
4. Auditory nerve

### Step 2: Analyze Each Option
- **Trochlear Nerve**: This nerve is responsible for eye movement. It primarily innervates the superior oblique muscle of the eye, which means it is involved in functions related to the head. Therefore, this option is incorrect.

- **Vagus Nerve**: This is the longest cranial nerve and is known for its extensive distribution throughout the body. It supplies various organs, including the heart, lungs, and digestive tract, and carries signals between these organs and the brain. This option is correct.

- **Oculomotor Nerve**: This nerve also plays a role in eye movement and controls most of the eye's movements, as well as the constriction of the pupil. Thus, it is also related to the head and is incorrect.

- **Auditory Nerve**: This nerve is responsible for hearing and balance. It does not supply any parts of the body other than those related to hearing, making this option incorrect as well.

### Step 3: Conclusion
After analyzing all the options, the correct answer is the **Vagus Nerve**, as it is the longest cranial nerve and supplies all parts of the body other than the head.

### Final Answer
The longest cranial nerve that supplies all parts of the body other than the head is the **Vagus Nerve**.

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