Anatomy of nerves coming from the brain and their paths

Seven pairs of nerves grow from the brain. The first pair grows from the depths of the two anterior ventricles of the brain and the place where there are two appendages, similar to the tips of the nipples, which carry out the sense of smell. These nerves are large, hollow; the one that grows on the left goes to the right, and the one that grows on the right goes to the left. Then they converge, intersecting crosswise, and the nerve growing on the right passes to the right pupil, and the one growing on the left goes to the left pupil. At the same time, their mouths expand, so that they embrace moisture, called vitreous. Some doctors, not Galen, say that these nerves pass through a cross, without bending.

Regarding this intersection, three benefits are said.

First, it exists so that the pneuma flowing to one of the pupils can flow unhindered to the other if damage occurs to one pupil. Therefore, each eye becomes more alert if the other eye is closed, and sees more clearly if it looks and the other does not look. For the same reason, the opening of the iris widens if you close your other eye. This happens because the pneuma flows forcefully into the open eye.

Secondly, the cross-shaped intersection exists so that both eyes have a single receiver, to which the eyes lead the outlines of a visible object. The outlines are connected there and the vision with both eyes becomes unified, since the image of the object is on the common vision boundary for both eyes. Therefore, cross-eyed people sometimes see one object as two objects, when one pupil deviates upward or downward and the straightness of the duct leading to the crossing is disrupted. Therefore, the nerve bends to a common border and another border appears.

Thirdly, the usefulness lies in the fact that one nerve props up and supports the other and it turns out as if they. grow from a place close to the eye.

The second pair of nerves emerging from the brain begins behind the beginning of the first pair and deviates from it in an outward direction. It emerges from their openings in the socket that encloses the eyeball and divides into the muscle of the eyeball. This pair is very thick, so that the thickness of the nerves can resist the softness due to their proximity to their origin, and the nerves have the power to move the eye, especially since they have no assistant, since the third pair is intended for the movement of a large organ, namely the lower jaw. Therefore, she does not have excess strength left, and on the contrary, she needs the help of another nerve, as we will say later.

As for the third pair, its origin is the common boundary between the anterior lobe of the brain and the posterior lobe in the direction from the base of the brain. At first it merges a little with the fourth pair, then leaves it and branches into four branches. One branch exits through the entrance of the carotid artery, which we will talk about later, goes down from the neck, passes the thoraco-abdominal obstruction and diverges in the viscera lying below the obstruction.

The second part comes out of a hole in the temporal bone. Moving away from the bone, it connects with the nerve, separated from the fifth pair, the location of which we will talk about later.

A branch of this pair emerges from an opening from which a second pair emerges, heading towards the organs located on the front of the face. It would be bad if it passed through the passage of the first, hollow pair of nerves and constricted and compressed the most important nerves, so that their cavity would be closed.

Moving away from the hole, this part is divided into three branches.

One branch deviates towards the corners of the eye and is released, heading to the temporal and masseter muscles, to the eyebrows, to the forehead and to the eyelids. The second branch passes into the hole created near the corners of the eye, is released, heading towards the inside of the nose, and is distributed in the layer of membrane lining the inside of the nose.

The third branch, and this is a considerable branch, descends to a cavity in the form of a canal prepared in the cheek bone, and branches into two branches. One of its branches goes into the oral cavity and is distributed in the teeth. As for the portion of the nerves that goes to the molars, it is clearly visible, while the portion of the other teeth is entirely hidden from view. This branching is also distributed in the upper gums. Another branch diverges in the outer part of the organs located here, such as in the skin of the cheek, at the tip of the nose and on the upper lip.

These are the branches of the third part of the third pair of nerves. As for the fourth branch of the third pair, it is released, passing through the opening of the upper jaw to the tongue, and diverges in its upper layer, giving it a special feeling, namely taste. The remaining nerves of this branch radiate in the gums of the lower teeth, in the lower part of the gums, and also in the lower lip.

The part of the nerves that goes to the tongue is thinner than the optic nerves, for the hardness of the first and the softness of the second determines the thickness of the second and the thinness of the first.

As for the fourth pair of nerves, it begins behind the third and deviates more towards the base of the brain. As we have already said, this pair merges with the third pair, then moves away from it and, freed, goes to the palate, to which it imparts sensitivity. This pair is small, but it is harder than the third, since the palate and the membrane of the palate are harder than the membrane of the tongue.

In the fifth pair, each nerve is split into two halves, as if doubled; According to most anatomists, each nerve of this pair is a pair of nerves, and they begin to grow on both sides of the brain, with the first part of each pair going to the membrane lining the inner cavity of the ear and completely diverging there. In fact, this part begins to grow from the posterior lobe of the brain and is responsible for the sense of hearing. As for the second part, which is smaller than the first, this part comes out of a hole made in the petrous bone, and this is the hole that is called “crooked” or “blind”, since it twists strongly and its path is tortuous. This hole is created in such a way with the aim of lengthening the distance and moving the end of the pair away from its beginning, so that before leaving the hole it acquires distance from its beginning, the consequence of which is density.

When this pair leaves the hole, it merges with the nerves of the third pair. Most of the nerves of both pairs go towards the cheek and vastus muscles, while the rest go to the muscles of the temples. Taste was created in the fourth nerve, and hearing in the fifth, because the instrument of hearing needs to be open, so that the path of air to it is not blocked, and the instrument of taste must be covered. This implies the need for the auditory nerve to be denser, and its origin is closer to the posterior lobe of the brain.

In the eye muscle, nature limited itself to one nerve, while in the temporal muscles the nerves are numerous only because the eye socket needs excess width, since the nerve conducting the power of vision must have excess thickness, because it needs to be hollow. And the bone installed to hold the eyeball would not have tolerated numerous holes.

As for the temporal nerves, 6 they need excess density. However, they do not need excess thickness; on the contrary, thickness would make it difficult for them to move. In addition, the passage they have in the petrous bone is hard and allows numerous holes.

As for the sixth pair, it grows from the posterior lobe of the brain and adjoins the fifth pair, being connected to it by membranes and ligaments, so that it is like one nerve. Then it leaves the fifth pair and comes out of the hole located at the end of the lambdoid suture, and divides before exiting into three parts, which together come out of this hole.

One part goes to the muscle of the pharynx and the root of the tongue to help the seventh pair move it, and the second part goes down to the muscle of the scapula and to nearby parts. Most of this pair branches in the broad muscle located on the scapula. This part is of a decent size; she passes, suspended, until she reaches her goal.

The third part, and this is the largest of all three parts, descends to the viscera along the ascending path of the carotid artery, to which it is attached and with which it is connected. When this pair is opposite the larynx, a branch is separated from it and approaches the laryngeal muscles, with their ends facing upward,

which raise the larynx and its cartilages. When it passes the larynx, another branch rises from it, going to the overturned muscles, the ends of which are directed downwards, and these are the muscles necessary to open and close the cup-shaped cartilage, for it must be pulled downwards. Therefore this nerve is called the recurrent nerve. It descends from the brain only because the spinal nerves, if they ascended, would necessarily rise from their origin obliquely, and not straight, and could not exert strong tension downwards.

This nerve was created in the sixth pair because the soft and soft-prone nerves in the pairs preceding the sixth have already dispersed through the muscles of the face, head and organs located on them, and the seventh pair does not descend straight like the sixth, but must certainly go at an angle.

Since the ascending recurrent nerve needs a strong support, like a pulley, so that the ascending part can go around it, receiving support from it, and since this support must stand straight, be hard, strong and smooth and be close, then such a support can serve only a large artery.

The ascending part of this branch, located on the left, meets this artery, straight and thick, and bends around it without requiring thorough fastening. As for the part emerging from the right, the large artery does not pass near it in its original form. On the contrary, it approaches it, having become thinner, for branches have departed from it. At the same time, she lost her straightness, as she went obliquely, leaning towards the armpit. It was therefore necessary to strengthen the nerve by giving it some support by means of the ligaments that attach the branch of the nerve to the artery in order to compensate for the lost thickness and straightness. The wisdom of moving this return branch away from its origin is that, as a result, it came closer to the place of suspension and that, moving away from its origin, it acquired strength. The strongest part of the recurrent nerve is that which diverges in both layers of the laryngeal muscle along with the branching of the accessory nerves.

Then the strong part of this nerve goes down and a branch branches off from it, diverging in the membranes and muscles of the abdominal barrier and chest, as well as in the heart, in the lungs and in the veins and arteries passing here. The remainder of the nerve passes through the thoraco-abdominal barrier, joins the descending part of the third pair of nerves, and they diverge in the films of the viscera, ending at the broad bone.

As for the seventh pair of nerves, it begins at the common border between the brain and spinal cord and is large
part of it leaves, branching in the muscles that move the tongue, and in the common muscle of the thyroid cartilage and lambdoid bone. The rest of it sometimes diverges into other muscles adjacent to this one, but this does not always happen. Since other nerves are used for other duties, and it is not good for there to be many holes in front and below, it is best if the movement of the tongue is carried out by the nerve coming from this place, since the sense of taste came to the tongue from another place.