Hello hello my dear anatomy students, how are you? Welcome to video number 300 of this channel easy anatomy by Juan José Sánchez and we will precisely talk about the real origin and apparent origin of the cranial nerves, it is the last video that I will make of the cranial nerves, see that in total I made about 22, 23, 24 videos and well I am very happy to have reached 300 videos and we still continue making videos daily to be able to finish the subject on time, well on time really for me, but I have been making anatomical content for quite a few years now so the real origins and apparent of the cranial nerves are described with each cranial nerve but there are students who sometimes quickly need to know what all the real origins are, the apparent origins that is why I am going to give them to you as a summary in this video, first we have to know what is the real origin; The real origin, as its name suggests, is the anatomical site, that is, it is the site where the nerves are actually originating. Those that, for example, are motor, have nuclei where, let's say, the order comes out that will tell the nerve to do its action.
, it is where the fibers of origin are, in the case of the motor nerves of that nerve, but it is also the anatomical site where the nerves that are sensitive arrive, okay? where they make the synapses, generally these centers that are what we call real origins are nuclei and for the majority of the cranial nerves these nuclei are from the brain stem, the only two nerves that leave this real origin in the brain stem are the olfactory and the optic that have their real origins outside the brain stem, what is going to happen? here there is a lot of confusion between different anatomical schools, some say from the sensory point of view that the real origin is the sensory nuclei that are at the level of the brain stem, everything we see here in blue, but when you read some other books they tell you that the The real origin is actually the place where the nerve originates sensitively, because since they are sensitive nuclei, it is assumed that the nerves are arriving but it is because before their arrival they already originated from somewhere , so that is why they will sometimes read in some texts that talk about the real origins, this happens with the sensitive nerves in the brain stem and other texts tell you about its real origins outside the brain stem, so it is a big difference.
I am going to take it more as the latarjet and latarjet speak it. He says that the majority of the sensory nuclei in the brainstem are the ones he takes as their real origin. Very well, do they remind you then that the exceptions are the first and second cranial nerves, when we talk about apparent origin?
Well, the origin where the nerve is apparently originating, that is, it is the anatomical site that for most cranial nerves is the brainstem where I begin to see the nerve, where it emerges, okay? where macroscopically I see it, of course I cannot see its nucleus of origin because it is something microscopic, it is something that is, let's say, in the depth of the brain stem, but it is the place where I begin to see the nerve as such, that is what We call the apparent origin , again the first and second cranial nerves, which are going to be the exceptions of all the cranial nerves in this aspect, I mean, have their apparent origins outside the brain stem, okay? because they are not considered structures, let's say derived from the brainstem, but rather they are considered extensions of the telencephalon; So we are going to start talking about each cranial nerve and I will quickly tell you the real origin and its apparent origin and more or less so that you know the functions of each origin because we are going to see cranial pairs that have a nucleus but we are going to see cranial pairs that have up to four or five nuclei, so in a general way I want to talk to you about how the motor nuclei are composed and how the sensory nuclei are composed, the motor nuclei that in this book Netter puts in red, are going to be arranged in two columns.
: a medial column that is closer to the midline, as shaded here in green, which is responsible for innervating the striated muscles of somitic origin, which is the really normal skeletal muscle, we are going to see the third cranial nerve, the fourth, the sixth and the twelfth, that is, the common oculomotor, the pathetic or troll, the sixth which is the abducens and the twelfth which is the hypoglossus, they They are responsible for innervating the muscle of somitic origin . Why are we going to differentiate them? because the lateral column that I put here in yellow, we are talking about where the motor nuclei is the one that is responsible for innervating the so-called branchiomeric muscles, which are the muscles derived from the bronchial arches or the pharyngeal arches, which then will be the fifth cranial nerve, we are going to see the seventh cranial pair and through this nucleus that would be the ambiguous nucleus, to the ninth, tenth and eleventh cranial pair, then see that the arrangement of these columns matters a lot because they are going to tell you more or less than which muscle groups they are going to innervate, that already has a very embryological connotation, from the sensory point of view we are also going to see that they are arranged in two columns, but a little inverted, why?
Because in this case the medial column that is given by the solitary tract is responsible for innervating the structures of mesodermal or endoderm origin, okay? more or less similar to what we were talking about about the branchial arches, while the lateral column, ah well, in what reaches the solitary tract they are going to make the seventh cranial nerve which is the facial, the ninth which is the glossopharyngeal and the tenth which is the vagus, however in the lateral column which is given by everything that is the trigeminal tract, that sensitive nucleus of the trigeminal that you see is quite long that is why we call it spinal trigeminal, it is the one in charge of receiving the Sensitivity of the structures of somitic origin that exist, for example like the face, is then practically given by the references mainly to the fifth cranial nerve, okay? Very well, then we are going to start talking about the olfactory nerve, we talk about its real and apparent origin in a short way and so we continue with all the 12 cranial nerves, but first do not go away from the video [Music] it is very important that you subscribe to the channel down here where you see that it says subscribe, you click on it and you are part of the more than 247 thousand subscribers, almost reaching 250,000, a quarter of a million and well, this way you make the channel grow a little more and they also have access to the 300 videos of anatomy that you will find there to this day .
We are talking about the olfactory nerve, the first cranial nerve, its real origin will be the bipolar cells that are found in the thickness of the olfactory mucosa, its non- apparent origin is the place where I begin to see what it emerges, the brain really is. where it is arriving, is the lower face of the olfactory bulb, remember that the olfactory nerve is really from the receptors to the bulb, because here it is called bulo and here it is called tract, so that is why it is said that the real origin that It is where the fibers really originate and their apparent origin is where they enter the brain, which is at the level of the olfactory bulb. When we talk about the optic nerve, we see that its real origin is at the level of the retinal ganglion cell layers, okay?
Remember that the optic nerve goes from here from the eye to the chiasm, so its apparent origin would be when it penetrates the chiasm specifically in the anterolateral corner of the optic chiasm. Did you see that it is quite easy to briefly study real origin and apparent origin? Remember that all nerves see that their real origin is really far outside the brain stem and that they are nerves that, let's say, are considered telencephalic extensions, okay?
To differentiate it from the other cranial nerves, both are clearly sensitive, they only capture stimuli, then we have the common oculomotor nerve, this common oculomotor nerve , the third cranial nerve, they also call it the common oculomotor nerve, it has two nuclei, one nucleus that is here I put them in green that we are going to see in the medial column, which is the somatomotor nucleus because they innervate muscles of somitic origin, such as the majority of the muscles of the cavity, let's say ophthalmic, the ocular cavity, okay? and then it has a parasympathetic nucleus that I put in yellow, which we call the accessory parasympathetic nucleus or it has a very eponym famous, which is the Edinger westphal nucleus, which is responsible for controlling the parasympathetic functions carried by the third cranial nerve, especially with respect to the pupil and especially with respect to the muscle that is responsible for regulating the lens, then these two muscles which would be the real origins of the motor oculus are found at the mesencephalic level, we are going to see that only two pairs have mesencephalic nuclei, which are the third and the fourth, the apparent origin well when I start to see it you see that it is in the anteromedial aspect of the mesencephalic peduncle, mesencephalic peduncle also called cerebral peduncle in that fossa where they are emerging is called the interpeduncular fossa in fact there is a groove that we sometimes call the oculomotor groove, precisely because of the apparent origin of this nerve, see where I start it Let's see, I can't see its core. Then we have the pathetic or trochlear nerve, which is a nerve that is also found in the depths of the midbrain with a single nucleus that is a motor nucleus, it is part of the medial motor column because it has a muscle that is actually of let's say somitic origin as it is.
It is the superior oblique of the eye, it is the only cranial nerve whose figure is going to be uncrossed so that when we see the apparent origin when I see, for example, this is a posterior view of the brain stem, when I see the left trochlear nerve, its origin real is a nucleus that is on the right side and the nucleus on the left side in this case will have as its apparent origin the trochlear nerve on the right side, it is the only nerve that is used in its fibers are accused before emerging then its apparent origin in the posterior surface of the midbrain above the superior medullary velum, ok? then the only mesencephalic nuclei are really the third and fourth; Let's talk now about the trigeminal, it has many nuclei, okay? It has four nuclei in total, in fact three of those four nuclei are sensitive because we know that the trigeminal is a predominantly sensory nerve, all of this, let's say the sensory nucleus, is a long tract that we call the mesencephalic spinous tract of the trigeminal, because it goes from the spinal cord.
spinal to the midbrain, see that it is very long, so we are going to divide these sensory nuclei, which are going to be three, into the same tract divided into three zones, first we talk about the spinal nucleus that is found in the medulla oblongata, it has a lot to do with the capture of thermoalgesic sensitivity, heat and cold, then we have the main nucleus, which is already at the bridge level, okay? It has more to do with, let's say, general sensitivities and then we have the mesencephalic nucleus, which is the most superior. This mesencephalic nucleus has more to do with proprioception and deep sensitivity, okay?
This spinal nucleus is sometimes given the connotation of sensitivity to pain, very well, what is happening? What I tell them depends on the book they read, some books will tell you that these are the real origin of the trigeminal but others tell you no, that the real origin is in the trigeminal ganglion, the gasser ganglion, which is where Let's say the origin of these nerve fibers that are entering the midbrain, however the motor ones leave the midbrain from the brainstem in which case, this motor nucleus that also has a trigeminal motor component that travels with the mandibular for the masticatory muscles mainly. It is located at the level of the bridge, okay?
Very good, what is the apparent origin? When do we start to see the trigeminal nerve? Well we see it on the anterolateral side of the bridge, it penetrates the thickness of the bridge; We now pass the sixth cranial nerve, which is the abducens nerve, it is a solely motor nerve, it has a motor nucleus that is specifically located at the level of the hindbrain in the most posterior part of the bridge and the emergence, let's say the apparent origin of this abducens nerve, also called External motor oculus is in the medullopontine sulcus, it is the sulcus that is between the medulla oblongata, which is the medulla oblongata, and the pons.
From that medulopontine sulcus we are going to see that three cranial pairs emerge, the most medial of the three and, like this, also the medulla. oblong, we also call it the medullo oblongata, sometimes one sees the name as the bulbopontine sulcus is the same medullopontine, bulbopontine; Then we have the facial nerve, that facial nerve also has several nuclei. First, I told you about the motor nucleus of the facial nerve, which is located in the part, let's say, of the bridge at the level of the hindbrain.
It has a nucleus that is sensitive and is responsible for the gustatory function. of the anterior two thirds of the tongue, also of the sensitivity of the tongue and this sensitive sensory nucleus is part of the solitary tract, we are going to see that apart from that it has two parasympathetic nuclei, one which is the superior salivary and another which is the lacrimal that is not seen in the image because they say in the books that it is part of the lower part of the superior salivary lacrimal nucleus, these parasympathetic nuclei are actually in charge of the facial, the superior salivary in turn is responsible for innervating the submaxillary glands and the sublingual and the lacrimal of the lacrimal gland, I forgot to tell you that it is well known that the motor nucleus is mainly responsible for the muscles of expression or facial mimicry, the apparent origin of the facial nerve which is made up of two components, let's say a facial nerve proper and the intermediate nerve, both emerging from the medullopontine sulcus a little more lateral than the abducens emerged; Then we have the vestibulo-cochlear nerve, I remind you that this eighth cranial nerve had two components, a vestibular component whose real origin will be in the vestibular ganglion, also called the scarpa nerve, while the cochlear nerve, which is responsible for hearing, is this vestibular is primarily responsible for balance, it has its real origin in the cochlear ganglion, which is in the cortical ganglion, which is several cortical ganglia, of which there are several, several dilations, however, the vestibular ganglion is one, in the end this nerve cochlear vestibule comes looking, see how it penetrates the brain stem looking for nuclei that are found there, such as the cochlear nuclei in the case of the cochlear nerve or the cochlear component, rather, and the vestibular component looks for the vestibular nuclei, then they can tell you that the origin real of these nuclei that are outside the trunk or you can tell them that they are the nuclei where they relay, but really the one that is real is more this one that is outside because where those nerve fibers are really originating, the fact is that the apparent origin does It will always be the same as it is at the level of the bulbopontine or medullopontine sulcus, the most lateral one from which this sulcus originates ; Then we move on to the nerves that have to do with the medulla oblongata, whose real origins are in the medulla oblongata. We start with the ninth cranial nerve, which is the glossopharyngeal nerve, which has three sensory nuclei.
Note, one is the spinal nucleus of the trigeminal nerve that is located at the level of the medulla oblongata, the other two are in the solitary tract, one in the middle third of the solitary tract and another in the most rostral portion of the solitary tract, these would then collect the sensitivity that the glossopharyngeal is collecting as the sensitivity of the pharynx of the posterior third of the tongue and the other structures that are in the glossopharyngeal nerve video, then, these are the so-called real origins from the point of view of the sensory nuclei, but some can tell you that the real origin is actually in these There are two ganglia because it is the first synapse that makes the sensory pathway, the motor nucleus, which is responsible for carrying out the glossopharyngeal motor functions, are given by the nucleus ambiguus, okay? We are going to see that this ambiguous nucleus has motor and sensory components, which is why they call it ambiguous, so in this case it gives the motor part to the glossopharyngeal, apart from that it has a parasympathetic nucleus, which is the inferior salivary nucleus, which is what gives it It takes the sensory fibers to the parotid gland, okay? then the superior salivary of the facial is for the submaxillary and sublingual gland and the inferior salivary is from the glossopharyngeal and is only for the parotid, the apparent origin is at the level of a groove that is behind the olive, which is the retro olivary groove.
, Although some books deny the existence of the retro olivary groove and say that it originates in an area behind the olive but that it is not the retro olivary groove, it depends on the book you read, but in the case of the latarjet, which is the one I use the most. For neuroanatomy, if you can figure it out, they talk about the retro olivary sulcus for the next three cranial nerves; Then we have the vagus, the vagus also has multiple nuclei, let's see what its motor nucleus is in the nucleus ambiguus, the same motor that used the glossopharyngeus, it has a sensory nucleus that is also found in the spinal nucleus of the trigeminal and has three parasympathetic nuclei because the vagus is a nerve that uses the parasympathetic, it is the nerve that the parasympathetic uses the most to distribute itself. What are these three parasympathetic nuclei?
We are going to see two in charge of the motor part that are considered viscero-motor nuclei, such as the dorsal nucleus of the vagus and the nucleus ambiguus, so that the nucleus ambiguus has a parasympathetic motor part and it has a motor part, let's say from a general point of view. and then we have a sensory visceral nucleus which is the solitary tract or the solitary nucleus that is found within the solitary tract, so in the long run you see that it will have two, plus three v, aa have five nuclei the vagus nerve, its apparent origin below the glossopharyngeus in the retro olivary sulcus, then we have the accessory nerve and here we end up with the eleventh cranial nerve, also called the spinal nerve. This accessory nerve, as it has two components, has a nucleus that originates from the one that forms the cranial root that is It originates in the medulla oblongata, which is in the lowest part of the nucleus ambiguus, so that the nucleus ambiguus serves the ninth, the tenth and the eleventh, okay?
and then it has a spinal component that comes from the cervical spinal cord, okay? so that 's why in the end we are going to see the real origin. The apparent origin, sorry, are two roots, a cranial root that comes from the retro olivary sulcus and then a spinal root that comes from the cervical spinal cord that originates in the posterolateral sulcus of the cervical cord, it is the only one of the cranial pairs that It has an apparent origin in the cervical spinal cord, okay?
very good, then we have, remember, well, I forgot to tell you, it is a totally motor nerve that mainly moves the sternocleidomastoid and trapezius muscles, although it has a component that joins the vagus and helps innervate the larynx and pharynx through the vagus and then We have the last fully motor cranial nerve, which is the hypoglossal nerve, it has a nucleus for the sole motor called the hypoglossal nucleus, it is a nucleus that is found in the depths of the medulla oblongata, its apparent origin is in the pre olivary sulcus, it is no longer like the other three that were retro olive groves, but they pre-oiled ahead of the olive.
