Medulla Oblongata Anatomy - External & Internal (White & Grey matter) + QUIZ
Summary
TLDRThis educational video script delves into the anatomy of the medulla oblongata, a vital part of the brainstem. It covers both external and internal features, highlighting the medulla's topography, grooves, bumps, and cranial nerve connections. The script also explores the medulla's internal grey and white matter, detailing the nuclei and tracts responsible for essential functions like voluntary muscle movement and balance. A quiz at the end challenges viewers' understanding, promising a comprehensive grasp of this complex brain region.
Takeaways
- 🧠 The central nervous system is composed of the encephalon and the spinal cord, with the encephalon further divided into the brainstem, cerebellum, diencephalon, and telencephalon.
- 🌟 The medulla oblongata is a critical part of the brainstem, situated above the spinal cord and below the pons, and it connects with the cerebellum.
- 📏 The medulla oblongata is approximately 2.5 cm in length and plays a significant role despite its small size.
- 👀 The anterior surface of the medulla features five grooves: the anterior median fissure, right and left anterolateral sulci, and right and left posterolateral sulci.
- 🔍 The pyramids of the medulla, located medially, contain corticospinal tracts responsible for voluntary skeletal muscle movement.
- 🔗 The olives of the medulla are lateral to the pyramids and are associated with the olivary nucleus.
- 💉 The 12th cranial nerve, the hypoglossal nerve, emerges from the anterolateral sulcus and controls most tongue muscles.
- 🔊 The glossopharyngeus, vagus, and accessory nerves emerge from the posterolateral sulci, serving swallowing, organ regulation, and neck muscle movement.
- 🔙 The posterior surface of the medulla includes the posterior median sulcus, gracile and cuneate fascicles, and inferior cerebellar peduncles.
- 🧬 The internal structure of the medulla consists of grey matter (nuclei) and white matter (tracts), with the grey matter containing cell bodies and the white matter containing nerve fibers.
- 🚀 Key tracts include the gracile and cuneate tracts for sensory information, spinocerebellar tracts for proprioception, and corticospinal tracts for voluntary muscle control.
Q & A
What are the two main parts of the central nervous system?
-The central nervous system consists of the encephalon and the spinal cord.
What is the medulla oblongata and where is it located?
-The medulla oblongata is a part of the brainstem located above the spinal cord and below the pons, and it connects with the cerebellum.
What is the length of the medulla oblongata?
-The length of the medulla oblongata is about 2.5 cm.
What are the two surfaces of the medulla oblongata?
-The medulla oblongata has an anterior surface and a posterior surface.
What are the five grooves found on the anterior surface of the medulla oblongata?
-The five grooves on the anterior surface of the medulla oblongata are the Anterior median fissure, Right and Left Anterolateral sulci, and Right and Left posterolateral sulci.
What structure contains the corticospinal tracts and is located between the anterior median fissure and the anterolateral sulci?
-The Pyramids of the Medulla Oblongata contain the corticospinal tracts.
Which cranial nerve is responsible for the movement of most of the muscles in the tongue?
-The 12th cranial nerve, the hypoglossal nerve, is responsible for the movement of most of the muscles in the tongue.
What is the function of the glossopharyngeus, vagus, and accessory cranial nerves that emerge from the medulla?
-The glossopharyngeus is for coordinating swallowing and the gag reflex, the vagus regulates functions of most organs through parasympathetic fibers, and the accessory nerve is for neck muscles.
What are the structures found on the posterior surface of the medulla oblongata?
-On the posterior surface of the medulla oblongata, you find the Posterior median sulcus, Gracile Fascicle, Cuneate Fascicle, and inferior cerebellar peduncles.
What are the functions of the gracile and cuneate nuclei within the medulla oblongata?
-The gracile nucleus receives sensory input from the lower part of the body, and the cuneate nucleus receives input from the upper part of the body.
How does the medulla oblongata contribute to the balance and posture of the body?
-The medulla oblongata contributes to balance and posture through tracts like the vestibulospinal tract, olivospinal tract, and reticulospinal tracts.
Outlines
🧠 Introduction to the Medulla Oblongata
This section introduces the anatomy of the central nervous system, focusing on the medulla oblongata. It explains the division of the central nervous system into the encephalon and the spinal cord, with further subdivision of the encephalon into the brainstem, cerebellum, diencephalon, and telencephalon. The medulla oblongata's position between the spinal cord and pons is highlighted, along with its connection to the cerebellum. The video promises to cover both the external and internal surfaces of the medulla, including its topography and structures visible from anterior and posterior views. The length of the medulla is noted as approximately 2.5 cm, emphasizing its small size but significant role in the brain.
👁️🗨️ Anatomy of the Medulla's External Surface
This paragraph delves into the external surface features of the medulla oblongata. It describes the anterior surface, which includes the anterior median fissure, anterolateral sulci, and posterolateral sulci. The Pyramids of the Medulla Oblongata, located medially, contain corticospinal tracts responsible for voluntary muscle movement. The Olives of the Medulla, laterally positioned, house the olivary nucleus. The paragraph also discusses the exit points of the 12th cranial nerve (hypoglossal nerve) and three other cranial nerves (9th, 10th, and 11th) from the sulci, detailing their functions. The posterior surface is then examined, featuring the posterior median sulcus, gracile fascicle, and cuneate fascicle, which are involved in sensory input from different parts of the body. The inferior cerebellar peduncles, connecting the cerebellum to the medulla, are also mentioned.
🔍 Internal Structure of the Medulla Oblongata
The internal surface of the medulla is explored in this section, distinguishing between grey matter (nuclei) and white matter (tracts). The grey matter includes the Gracile Nucleus, Cuneate Nuclei, olivary nuclei, and the Reticular Formation. The white matter consists of tracts such as the inferior cerebellar peduncle, which connects to the cerebellum. The discussion continues with the function of various tracts, including the ascending sensory tracts (gracile and cuneate fascicles) and the descending motor tracts (corticospinal tract). The decussation of the pyramids, where many corticospinal tract fibers cross, is also explained. The summary provides a detailed look at how these structures facilitate different sensory and motor functions within the brainstem.
🌐 Tracts and Nuclei within the Medulla
This paragraph provides a comprehensive overview of the various tracts and nuclei found within the medulla oblongata. It describes the function of ascending tracts like the spinocerebellar tracts, which contribute to unconscious proprioception, and the spinothalamic tracts, which transmit conscious sensory information related to pain, temperature, and touch. The descending tracts are also detailed, including the corticospinal tract responsible for voluntary muscle movement, the vestibulospinal tract for balance and posture, and the olivospinal tract, which aids in balance. Other tracts like the rubrospinal, tectospinal, and reticulospinal tracts are also covered, emphasizing their roles in fine motor coordination, eye and neck muscle coordination, and balance, respectively. The medial longitudinal fascicle, which coordinates involuntary head and neck movements, is also mentioned. The paragraph concludes with a challenge for viewers to recall the functions and pathways of the numbered structures without visual aids.
Mindmap
Keywords
💡Central Nervous System
💡Medulla Oblongata
💡Brainstem
💡Cerebellum
💡Anterior Surface
💡Posterior Surface
💡Grey Matter
💡White Matter
💡Cranial Nerves
💡Corticospinal Tract
💡Reticular Formation
Highlights
The central nervous system consists of the encephalon and the spinal cord.
The brainstem is composed of the medulla, pons, and midbrain.
The medulla oblongata is a critical part of the brainstem.
The medulla's external surfaces include anterior and posterior views.
The anterior surface of the medulla features five grooves.
The Pyramids of the Medulla Oblongata contain corticospinal tracts.
The Olives of the Medulla contain the olivary nucleus.
The 12th cranial nerve, the hypoglossal nerve, emerges from the medulla.
Cranial nerves 9, 10, and 11 exit from the posterolateral sulci.
The posterior surface of the medulla forms part of the rhomboid fossa.
The medulla's internal surface is divided into grey and white matter.
The Gracile and Cuneate Nuclei are part of the medulla's grey matter.
The medulla contains tracts for both ascending and descending nerve fibers.
The corticospinal tract is a major descending tract in the medulla.
The vestibulospinal tract is involved in balance and posture.
The reticulospinal tract originates from the reticular formation.
The medial longitudinal fascicle coordinates head and neck movements.
Transcripts
What’s up. Meditay Here. Let’s continue the anatomy of the Central Nervous System.
In this segment, we’ll cover the complete anatomy of the medulla oblongata.
So remember, the central nervous system consists of two parts:
the encephalon and the spinal cord. The encephalon is then further divided into specific parts.
We have the brainstem, which consists of the medulla, pons, and the midbrain or the
mesencephalon. We have the cerebellum back here, then the diencephalon and the telencephalon.
Our focus in this video is going to be the medulla oblongata, which is here.
So in this video, we’re first going to cover the external surfaces of the medulla. Basically,
look at its topography and what structures you’ll find from an anterior view and a posterior view.
Then we’re gonna slice up the medulla and look at the internal surface.
Basically, see how the grey matter and white matter are arranged within it. And at the end
of this video, you’ll find a quiz that you’ll hopefully be able to pass based on this video.
Alright, so we can start by replacing this picture with a more realistic one.
The medulla is here, lying right above the spinal cord and below the pons. The medulla also connects
with the cerebellum, so you’ll find the cerebellum behind the superior part of the medulla oblongata.
And all of these structures lie within our cranial cavity within the skull.
So topographically, the medulla starts at the level of the foramen magnum,
which is the distinct border between the spinal cord and the medulla. And in the front,
the medulla lies on the clivus, which remember is at the anterior portion of the occipital bone.
The length of the medulla oblongata is about 2,5cm, so it’s a quite small portion
of your brain but a very important one. Alright. Now. Externally, your medulla has
two surfaces. It has an anterior surface and a posterior surface. Let’s now cover the typical
morphology of these two surfaces, starting with the anterior surface first. So if we look at the
brainstem from this perspective, you’ll see this. And again, the medulla oblongata is here in green.
So there are 5 grooves that you can see on the anterior surface. The first one is the Anterior
median fissure, then laterally to that, you can see the Right and Left Anterolateral sulci,
and laterally to that again, you’ll see the right and left posterolateral sulci.
And notice between these grooves, there are bumps that are very characteristic for the medulla.
The first bumps are called the Pyramids of the Medulla Oblongata. And they’re located medially
between the anterior median fissure and the Right and Left anterolateral sulci. The pyramids contain
the corticospinal tracts, which come from the pyramidal cells of the primary motor cortex. Which
remember is responsible for voluntary movements of our skeletal muscles. A majority of the fibers in
the corticospinal tract will decussate at the lower border, forming the decussation
of the pyramid. We’ll talk more about that when we talk about the internal surface of the medulla.
I just mentioned it now to give you something to remember the pyramids with. Alright. Laterally to
the Pyramids, you’ll find the Olives of the Medulla, which contain the olivary nucleus.
So these are the bumps. But some cranial nerves go out from the medulla through these grooves.
We have 12 cranial nerves in our body and each serves its particular function in the brain,
but from the anterior part of the medulla. You’ll see the 12th cranial nerve, the hypoglossal nerve,
going out from the anterolateral sulci. The 12th cranial nerve is responsible for the movement of
most of the muscles in your tongue, so this nerve goes out from the anterolateral sulcus
and then goes to the tongue. So that is that. Then on the posterolateral sulci,
there are three cranial nerves that go out. These are the cranial nerve number 9, number 10,
and number 11. The glossopharyngeus, Vagus, and the Accessorius. Glossopharyngeus is mainly for
coordinating the swallowing process and is also responsible for the gag reflex.
Vagus goes to most organs in your body and regulates their function. Mainly parasympathetic
fibers. And the last accessories is an accessory nerve for the neck muscles.
So that is the anterior view. Now let’s turn the picture around
and look at the posterior view. So the posterior part of the medulla is highlighted in green,
and if we now remove the cerebellum, you'll be able to see the rest of the medulla. Now
the upper part of the medulla oblongata takes part in forming the so called rhomboid fossa, which is
a fossa that contain many nuclei. The lower part of the rhomboid fossa is considered a part of the
medulla oblongata, but we’ll cover the rhomboid fossa briefly in a separate video to really focus
on the anatomy of the medulla for now. So on the posterior surface,
you’ll find the Posterior median sulcus. On either side of the posterior emdian sulcus,
you’ll find the Gracile Fascicle, remember we talked about this one when we talked about
the spinal cord. The gracile fascicle received sensory input form the Lower part of your body,
and sends it up through the spinal cord and through the medulla, to the gracile nuclei,
which form a gracile tubercule. Laterally to the gracile fascicle is the Cuneate Fascicle,
which receives input from the upper parts of your body and forms the Cuneate Tubercle.
From the posterior surface of the medulla, you’ll also be able to see the inferior
cerebellar peduncles, which are fibers that go within the medulla, to the cerebellum, as you
see here. So the inferior cerebellar peduncles connect the cerebellum and the medulla together.
So that was all for the external surface of the medulla.
Now let’s go ahead and cover the internal surface of the medulla oblongata.
The internal surface of the medulla consists of two parts, grey matter, and white matter. And
just to remind you again, that grey matter always contains cell bodies, so when we talk about the
grey matter, we talk about nuclei. White matter always contains nerve fibers, which form tracts.
Now, let’s finally take the medulla and give it a good slice, to focus on the internal surface. In
theory, if you wanna go deep within the neurology of it, the internal surface of the medulla differs
along the superior part and the inferior part of it. Meaning if you cut the medulla at different
regions, you’ll find different structures. But in this video, I’ll just slice at the superior part
of the medulla and talk about the most significant parts of the internal surface while highlighting
which parts below to which level so that it gets easier to understand the medulla oblongata.
So here is the general outline of the medulla. We’ll be able to see the Antrior median fissure,
the Pyramid of the medulla and the Olives. And posteriorly, we’ll see the Gracile Tubercle and
the Cuneate Tubercle. And on the sides here we can see the inferior cerebellar peducle,
which remember connects the cerebellum with the medulla. So I hope you’re following so far. Let’s
now go ahead and fill upp the internal surface with structures, starting with the grey matter.
We’re first going to have the Gracile Nucleus medially, within the gracile tubercle. Then
laterally to that, we have the Cuneate Nuclei, within the cuneate Tubercles. Within the Olives,
we have the olivary nuclei, and then in the middle, we have the Reticular formation,
which is a network of grey matter throughout the brainstem. I’ll show you this in a little
more detail later. Then lastly, you’ll find many nuclei of the cranial nerves within the medulla,
at the region of the Rhomboid Fossa. You’ll find the cranial nuclei number 8-12. Again,
these are not significant for the understanding of the medulla anatomy, for now, so I’ll mention
these in the video about the rhomboid fossa. So these are the grey matter of the medulla
oblongata. Let’s now see how these nuclei are associated with tracts within your brainstem
by looking at the white matter of the medulla. While we’re talking about the tracts,
I’ll represent the blue color as ascending tracts or sensory tracts. And the red color
will represent motor tracts or descending tracts. Alright, so first off, we’ll start with the
fibers associated with the nucleus gracilis, and we’ll add the spinal cord to visualize this one.
Fibers that synapse with the nucleus gracilis are sensory fibers that come from the lower parts of
the body and through the spinal cord. These fiber will then ascent and synapse with nucleus gracilis
in the medulla. Um, I use the letter G in Gracile nucleus as genitals to remember that nucleus
gracilis receives input from the lower parts of the body. And it receives conscious epicritic
sensibility. With is conscious proprioception. Remember, this is kinesia, joint position,
and the sense of force. But it also receives input from mechanoreceptors, which is responsible for
two-point discrimination, which means the minimal distance between two points required for you to
detect it as two points and not one. So if these two pencils were veeery cloe to each other, you’d
have detected that prick as one point and not two. So two-point discrimination is your ability
to discriminate between two points. Meaning the minimum distance needed for you to sense those
pencils as two points, not one. It also receives input like vibration and touch. All of these are
sent to the nucleus gracilis. The cuneate nucleus receives input from the upper part of your body
through the cuneate fascicle, which also senses epicritic sensibility. Alright. Now from the
gracile nucleus and the Cuneate nucleus, where do the fibers go? Well, they split into two pathways.
They split into fibers that go through the inferior cerebellar peduncle, as you see here,
as fibers called the external arcuate fibers. And remember, since they go through the inferior
cerebellar peduncle, they’ll go to the cerebellum. Now. Since we have external arcuate fibers,
we’ll also have internal arcuate fibers. And these fibers will cross over to the other side,
as you see here. So these are called the internal arcuate fibers. And since both sides cross to the
other side, they decussate to form the decussation of the lemnisci. They’re called that because once
they cross, they start to ascend upwards in your CNS, as the medial lemniscus. To go
further through the diencephalon and then to the primary somatosensory area in the cerebral cortex.
Next, we have two tracts on either side. Called the spinocerebellar
tracts. Remember we talked about these when we talked about the spinal cord?
We have an anterior spinocerebellar tract and a posterior spinocerebellar tract. Remember, if the
tract ends with the work Cerebellum, that means that these tracts will ascend to the cerebellum.
But the way these two tracts do that is a little bit different. The posterior spinocerebellar
tracts are closest to the inferior cerebellar peduncle, so it’ll go through the inferior
cerebellar peduncle to the cerebellum. The anterior spinocerebellar tract
will ascent through the medulla oblongata through pons and then to the midbrain. From the midbrain,
it’ll go into the cerebellum through the superior cerebellar peduncle.
And since these tracts go to the cerebellum, that means they’re responsible for
unconscious proprioception, like giving information about the posture and joints.
After that we have two other ascending tracts, called Spinothalamic tracts.
We have an anterior spinothalamic tract and a lateral spinothalamic tract. These tracts
are both going to go to the primary somatosensory area in the cortex. And as they ascent, they get
the name the spinal lemniscus. And since they go to the cerebral cortex, that means they provide
conscious sensory information. And that is for Pain and temperature and pressure and touch.
So that was all the ascending tracts I wanted to mention in the medulla.
Now let’s do the descending tracts. And the first one is the one that’s
the most significant of them, located within the pyramids of the medulla, called the corticospinal
tract. These fibers will originate from the pyramidal cells of the primary motor cortex,
and then they will descend. 80 percent of the fibers that descend, will cross at the
medulla oblongata region, like this, and form the deccusation of pyramids. After they cross, they
will descend as the lateral corticospinal tract. The remaining 20% will descend as the anterior
corticospinal tract, and only decussate at the region they exit at the spinal cord. And since
they come from the pyramidal cells of the primary motor cortex, that means they’re responsible
for the voluntary movement of skeletal muscles. Next there are the corticonuclear tracts, which
descend at the same areas as the corticospinal tract. And the corticonuclear tracts are
responsible for the voluntary control of muscles located in the head and neck.
The next descending tract is the vestibulospinal tract. Inside of your ear, the inner ear,
you have a system called the vestibular system. The vestibular system has crystals within it
sensing the position of your head, wether your head is tilted upside down, or to the side, all of
that is sensed and through the vestibular nerve, it’s sent to the brainstem, and then down to your
spinal cord to keep your balance and posture. So the vestibulospinal tract is responsible for
keeping your balance and posture. And this happens unconsciously because this tract doesn’t originate
from your cortex—so unconscious balance of your body is the function of this tract.
So that is the Vestibulospinal tract. Next we have the Olivospinal tract, which comes from the
olivary nuclei. The olivospinal tract also takes part in helping you keep your balance and posture.
Through the olivary nuclei, there are also fibers that go to the cerebellum,
called the olivocerebellar tract, which aid the balance system. So that’s these.
Next, we have the Rubrospinal tract. Rubro means red, and the reason why they’re called rubrospinal
tract Is because we have red nuclei located inside the midbrain of the brainstem. So these fibers are
extrapyramidal because they’re not originating from the primary motor cortex. They come
from the red nucleus of the midbrain, and they descend as the rubrospinal tract. And remember,
extrapyramidal fibers are responsible for fine coordination of movements and support voluntary
movements, they make our voluntary movements more precise. SO that is the rubrospinal tract.
The next tract is the tectospinal tract. It transmits motor impulses for the eyes and
neck muscles. So they coordinate the eyes and the neck muscles when you look at something.
Imagine you’re looking at a hamburher, you look at it, and you keep looking at it as it passes you
and your neck muscles follow your eyes. That’s what this tectospinal tract is responsible for.
It’s called tectospinal tract because it comes from the tectum of the midbrain, it’s located
on the posterior surface of the midbrain. It’s also extrapyramidal, so it unconsciously
moves your neck muscles with your eyes. Then we have the Reticulospinal Tract.
We have a lateral Reticulospinal tarct, and a medial reticulospnal tract, which are also a
part fo the balance and posture system. They come from the reticular formation inside the brainstem.
The Reticular system are responsible for Sleep, alertness, cardiovascular control,
breathing and all of those vital things. But they’re also responsible for motor control
like your balance and posture, through the reticulospinal tract. So that is all of these.
Let’s just clean up the labels and add a little colour to differentiate them.
There is one more tract that we need to mention, which is the medial longitudinal fascicle,
which descend and is present only in the cervical segments, which coordinated involuntary movements
of the head, neck, and eyes through synapses between the cranial nerves 3,
4, 6, and 11. So that was all I had for the internal surface of the grey and the white matter.
I made this table for the nuclei in the grey matter and the tracts in the white matter we
just went through, along with a little description of them. Now this Is where this video gets scary.
I am going to make all of these names disappear, and can you, from the beginning, tell me what is
the name of number 3, what is the name of number 4, where does number 6 go and where does number 11
go. If you can do that, then you’ve grasped the anatomy of the medulla oblongata fully.
If you found this video helpful, please put a like, comment, share, whatever
you find convenient to you. The next video is going to be about the Pons
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