The 12 cranial nerves: where each one leaves the brain
There are 12 pairs, numbered I to XII from front to back by where they leave the brain. I and II join the forebrain; the other ten leave the brainstem: III and IV the midbrain, V the pons, VI to VIII the pons–medulla border, IX to XII the medulla (XI also the upper spinal cord). [1][2]
Drawn as their own shape: II optic, III oculomotor and IV trochlear. Shown only by where they leave: I and V–XII.
The 3D brain needs JavaScript. The table below still says where each nerve leaves the brain.
The brain starts turned so you look at it from the front and below, where most of the nerves leave. Drag to turn, pinch or scroll to zoom; tap a nerve in the table to light where it leaves; .
What the model can show. It has a shape of its own for only three of the nerves: the optic nerves and their chiasm (II), the oculomotor nerves (III, only their two branches inside the eye socket, not the stretch from the midbrain) and the trochlear nerves (IV, the whole nerve from beside the midbrain to the eye socket). Every other nerve is shown by the part it leaves from, never by a marker at a guessed point. The olfactory bulb (I) is not a shape in this atlas, so row I lights the orbitofrontal cortex, the underside of the frontal lobe the bulb lies against. The spinal cord is drawn only as the top of its central canal, about 6 mm below the medulla, so row XI lights that as the upper spinal cord. [3][4][5]
The 12 cranial nerves, in order
Tap a row, or move to its button with Tab and press Enter, to light where that nerve leaves the brain.
Not from the brainstem: its fine fibres rise from the lining of the nose through the cribriform plate of the skull and end in the olfactory bulb, under the front of the brain. The bulb is not a shape in this atlas; lit: the orbitofrontal cortex it lies against. [6][4]Lights: orbitofrontal cortex (red) — the nerve is not a shape in this model. On its own page: orbitofrontal cortex.
Not from the brainstem: from the back of each eye it runs through the optic canal to the optic chiasm under the front of the brain, where about half its fibres cross; the optic tracts then carry on to the thalamus. [7][1]Lights: optic nerve (red) and optic chiasm (red) — the nerve itself is drawn.
Vision: it carries everything the retina sees. [7][2]
The front of the midbrain, in the hollow between the two cerebral peduncles (the interpeduncular fossa). [8]Lights: midbrain (yellow) and oculomotor nerve (red) — the nerve itself is drawn. On its own page: midbrain.
Works four of the six muscles that turn each eye (the superior, inferior and medial rectus and the inferior oblique), lifts the upper eyelid, and narrows the pupil and focuses the lens. [8][2]
The back of the midbrain, just below the inferior colliculi: the only cranial nerve to leave the back of the brainstem. It then winds forward round the midbrain. [9]Lights: midbrain (yellow) and trochlear nerve (red) — the nerve itself is drawn. On its own page: midbrain.
Works one eye muscle, the superior oblique, which turns the eye down and inward. It has the fewest nerve fibres of any cranial nerve. [9][2]
The side of the pons, as a large sensory root and a small motor root, where the pons joins the middle cerebellar peduncle. [10]Lights: pons (blue) — the nerve is not a shape in this model. On its own page: pons.
Feeling (touch, pain, temperature) from the face, mouth and inside of the nose, and the muscles of chewing. It is the largest cranial nerve. [10][2]
The border of these two lit parts, the pons and the medulla (the pontomedullary junction), close to the midline, inward of the facial nerve. [11][1]Lights: pons (blue) and medulla oblongata (green) — the nerve is not a shape in this model. On its own page: pons, medulla oblongata.
Works the lateral rectus, the muscle that turns each eye outward. [11][2]
The border of these two lit parts, the pons and the medulla, further out to the side than the abducens, in the angle between the pons and the cerebellum (the cerebellopontine angle). [12][1]Lights: pons (blue) and medulla oblongata (green) — the nerve is not a shape in this model. On its own page: pons, medulla oblongata.
Works the muscles of facial expression, carries taste from the front two-thirds of the tongue, and drives the tear glands and two of the salivary glands (the submandibular and sublingual). [12][2]
The border of these two lit parts, the pons and the medulla, just outside the facial nerve, in the cerebellopontine angle. [13][1]Lights: pons (blue) and medulla oblongata (green) — the nerve is not a shape in this model. On its own page: pons, medulla oblongata.
Hearing, from the cochlea, and balance: the sense of head position and movement from the vestibular organs of the inner ear. [13][2]
The side of the upper medulla, as rootlets in the groove behind the olive, just above the vagus nerve. [14]Lights: medulla oblongata (green) — the nerve is not a shape in this model. On its own page: medulla oblongata.
Taste and touch from the back third of the tongue and the throat, one throat muscle used in swallowing (the stylopharyngeus), the parotid salivary gland, and signals on blood pressure and blood oxygen from the carotid sinus and carotid body. [14][2]
The side of the medulla, as a row of rootlets in the groove behind the olive, below the glossopharyngeal nerve. [15]Lights: medulla oblongata (green) — the nerve is not a shape in this model. On its own page: medulla oblongata.
The parasympathetic supply to the heart, lungs and most of the gut, the muscles of the throat and voice box, and feeling from the organs of the chest and abdomen. It is the longest cranial nerve, reaching into the abdomen. [15][2]
Mostly the upper spinal cord: rootlets from about its top five or six segments join and rise through the foramen magnum into the skull. A small cranial root from the side of the medulla is often counted as part of the vagus instead. [16][1]Lights: medulla oblongata (green) and spinal cord (central canal) (red) — the nerve is not a shape in this model. On its own page: medulla oblongata, spinal cord (central canal).
Works two neck and shoulder muscles: the sternocleidomastoid, which turns and tilts the head, and the trapezius, which shrugs the shoulder. [16][2]
The front of the medulla, as rootlets in the groove between the pyramid and the olive. [17]Lights: medulla oblongata (green) — the nerve is not a shape in this model. On its own page: medulla oblongata.
Works the muscles of the tongue (all but one, the palatoglossus), for speaking, chewing and swallowing. [17][2]
How the twelve are counted and named
Cranial nerves are the nerves that come directly from the brain rather than from the spinal cord. Each of the twelve is a pair, one on each side, and the Roman numerals follow the order in which they leave the brain from front to back. [1]
The olfactory (I) and optic (II) nerves come from the forebrain; the other ten pairs arise from the brainstem, which is why ten of the twelve rows light the midbrain, pons or medulla. [1]
The olfactory and optic nerves differ from the rest: the optic nerve is a tract of the central nervous system wrapped in the brain's own coverings (the meninges), not a peripheral nerve in the strict sense. [7][1]
A thirteenth small nerve, the terminal nerve (sometimes called cranial nerve 0), runs next to the olfactory nerve; it is not counted among the classic twelve. [1]
Many of the nerves leave the skull through openings in its base: for example the olfactory fibres pass through the cribriform plate, the optic nerve through the optic canal, III, IV and VI through the superior orbital fissure, and IX, X and XI together through the jugular foramen. [1][2]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); it draws only some nerves as shapes, so the others are shown by the part they leave from.