This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuro Ophthalmology, Subject name: Ophthalmology
Which of the following pa of optic nerve is longest? 
Select and explain. 
A. Intraorbital, B. Intraocular, C. Intracranial, D. Intracanalicular
A: Intraorbital
Answer: A: Intraorbital 
Explanation: Intra-orbital is the longest pa of optic nerve. Cranial Nerve Optic nerve arises from ganglion cell axons. Length = 50 mm. (40 mm in few texts) Can be considered as pa of brain 2nd order neuron Pas: Intraocular(1), Intraorbital(2), Intracanalicular(3), Intracranial(4). Smallest pa of optic nerve is Intraocular Longest pa : Intraorbital.