Anatomy study note · Head and neck

Trochlear nerve

The fourth cranial nerve (motor), the slenderest cranial nerve. It supplies only the superior oblique muscle.

Key points

• CN IV: superior oblique only.
• Slenderest nerve; emerges from the back of the midbrain.
• Palsy: double vision on looking down.
• IV: somitomere 3.
• Motor nuclei: basal lamina. Sensory nuclei: alar lamina.
• Nerve: epineurium → perineurium (blood–nerve barrier) → endoneurium.
• Cut nerve: Wallerian degeneration; regrows 0.5–3 mm/day.

The full note in the atlas also covers

Course · Histology · Development · Clinical notes

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Written from

• Snell’s Clinical Anatomy by Regions, 10th ed., ch. 12, PDF pp. 1665, 1684
• Inderbir Singh’s Human Embryology, ch. 17, PDF pp. 312, 318; ch. 9, PDF p. 126
• BRS Cell Biology & Histology, 7th ed., ch. 9, PDF pp. 163–166, 166, 171–172

More from the head and neck

• Veins of the face and scalp
• Ventricles of the brain
• Vertebral and basilar arteries
• Vestibulocochlear nerve
• Vitreous body
• Zygomatic bone
• Abducens nerve
• Accessory nerve
• Anterior cerebral artery
• Aqueous humour
• Arteries of the face
• Arytenoid cartilage

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