Anatomy of the Heart - External & Internal Structures
Summary
TLDRThis educational video script delves into the anatomy of the heart, starting with blood circulation and moving on to the external and internal structures of the organ. It explains the pulmonary and systemic circulations, the heart's chambers, and the valves that regulate blood flow. The script also covers the heart's surfaces, sulci, and septa, providing a comprehensive understanding of the heart's function and structure.
Takeaways
- 💓 The heart has four chambers: right and left atrium, and right and left ventricle.
- 🔄 Blood circulation involves two main pathways: Pulmonary Circulation (heart to lungs and back) and Systemic Circulation (heart to body and back).
- 🔵 Deoxygenated blood enters the heart through the superior and inferior vena cava into the right atrium, represented in blue.
- 🔴 Oxygenated blood returns to the heart through the pulmonary veins into the left atrium, represented in red.
- 🫀 The right ventricle pumps blood to the lungs via the pulmonary valve and artery for oxygenation.
- 📍 The heart is located in the mediastinum, between the lungs, and has an apex directed forward and downwards to the left, and a base directed backward and to the right.
- 🏗️ The heart's external structure includes the Coronary Sulcus, which separates the atria from the ventricles, and the Anterior and Posterior Interventricular Sulci, which separate the ventricles.
- 🔍 The heart's internal structure includes the Interventricular Septum and Interatrial Septum, which divide the ventricles and atria, respectively.
- 🛡️ Valves such as the tricuspid, bicuspid (mitral), and aortic valves are crucial for preventing blood backflow and ensuring unidirectional flow.
- 💪 The right ventricle has a rough inner layer called Trabeculae carneae, which helps prevent blood from swirling and forming air bubbles.
- 🔑 The heart's anatomy can be understood by recognizing its external features such as the Coronary Sulcus and the sulci that separate the chambers.
Q & A
What is the primary focus of the video script?
-The video script primarily focuses on explaining the anatomy of the heart, including its external and internal structures, and the blood circulation within the body.
What are the two main types of blood circulation discussed in the script?
-The two main types of blood circulation discussed in the script are Pulmonary Circulation and Systemic Circulation.
How does the deoxygenated blood enter the heart according to the script?
-The deoxygenated blood enters the heart through the superior and inferior vena cava into the right atrium.
What is the function of the tricuspid valve?
-The tricuspid valve allows blood to flow from the right atrium to the right ventricle and prevents backflow of blood.
What is the significance of the Interventricular Septum?
-The Interventricular Septum separates the two ventricles and is crucial for preventing the mixing of oxygenated and deoxygenated blood.
What is the role of the papillary muscles in the heart?
-The papillary muscles are connected to the tendinous chords, which in turn attach to the valve cusps, helping to control the opening and closure of the valves.
What is the difference between the right and left ventricles in terms of their function in the blood circulation?
-The right ventricle pumps blood through the pulmonary valve into the pulmonary artery for oxygenation in the lungs, while the left ventricle pumps oxygenated blood through the aortic valve into the aorta and then to the rest of the body.
What is the term used for the inner layer of the heart that helps prevent blood from swirling and forming air bubbles?
-The inner layer that prevents blood from swirling and forming air bubbles is called the Trabeculae carneae.
What are the three surfaces of the heart mentioned in the script?
-The three surfaces of the heart mentioned in the script are the Pulmonary Surface, the Sternocostal Surface, and the Diaphragmatic Surface.
What is the function of the sinuses in the heart?
-The sinuses in the heart, such as the sinus of the pulmonary trunk, are spaces formed by the semilunar valves that help in the tight closure of the valves and prevent backflow of blood.
What is the term for the opening between the right atrium and the right ventricle, and what guards this opening?
-The term for the opening between the right atrium and the right ventricle is the Right Atrioventricular Orifice, and it is guarded by the tricuspid valve.
Outlines
🧡 Introduction to Heart Anatomy and Blood Circulation
This paragraph introduces the topic of heart anatomy and sets the stage for a detailed exploration. Meditay begins by explaining the purpose of the video, which is to discuss the heart's anatomy, starting with blood circulation and moving on to external and internal structures. The heart's position in the mediastinum is highlighted, and the importance of understanding blood circulation for grasping heart anatomy is emphasized. The paragraph concludes with an overview of the two types of blood in the body: deoxygenated and oxygenated, and how they enter and exit the heart through specific chambers and valves.
🔍 Dissecting the Heart's Chambers and External Features
This section delves into the heart's external features and the chambers within. It describes the heart's position, with its apex pointing downwards and forwards, and the base connected to major vessels. The heart's surfaces are outlined, including the pulmonary surface, sternocostal surface, and diaphragmatic surface, with a note on the variability in the number of surfaces described by different sources. The paragraph also discusses the significance of external sulci in locating internal chambers and the importance of the septum in separating oxygenated and deoxygenated blood within the heart.
🔬 Detailed Examination of the Right Atrium and Ventricle
The focus shifts to the right side of the heart, detailing the anatomy of the right atrium and ventricle. The right atrium's walls are explored, including the anterior wall with the right auricle, the superior wall with the opening for the superior vena cava, the posterior wall with the inferior vena cava opening and sinus venarum, and the medial wall featuring the interatrial septum and oval fossa. The right ventricle's triangular shape is described, along with its internal structures like the tricuspid valve, papillary muscles, and trabeculae carneae. The paragraph also explains the function of the pulmonary valve and the sinuses of the pulmonary trunk.
🌐 Left Atrium and Ventricle: The Oxygenated Side of the Heart
The narrative moves to the left side of the heart, examining the left atrium and ventricle. The left atrium is characterized by its smooth walls, the interatrial septum, and the openings for the pulmonary veins. The left ventricle is described with its base featuring the left atrioventricular opening guarded by the bicuspid (mitral) valve and the aortic opening leading to the aorta. The paragraph explains the function of the mitral valve, the structure of the left ventricle, including the papillary muscles and tendinous chords, and the aortic valve's composition of three semilunar cusps. The summary concludes with an overview of the systemic and pulmonary circulation, emphasizing the heart's role in oxygenating the body's blood.
Mindmap
Keywords
💡Anatomy of the heart
💡Blood circulation
💡Chambers
💡Valves
💡Pulmonary Circulation
💡Systemic Circulation
💡Septum
💡Pectinate Muscle
💡Trabeculae carneae
💡Sinus
💡Endocardium
Highlights
Introduction to the anatomy of the heart and its importance for understanding blood circulation.
Explanation of the heart's location in the mediastinum and its connection to the great vessels.
Overview of the blood circulation pathways, distinguishing between deoxygenated and oxygenated blood.
Description of the Pulmonary Circulation, detailing the process of oxygen exchange in the lungs.
Clarification of the Systemic Circulation, explaining how blood is pumped from the heart to the body and back.
Unique feature of pulmonary circulation where arteries carry deoxygenated blood and veins carry oxygenated blood.
Identification of the heart's apex and base, and their respective positions and connections.
Discussion on the heart's surfaces, including the Pulmonary Surface, Sternocostal Surface, and Diaphragmatic Surface.
Importance of the Coronary Sulcus in distinguishing between the ventricles and atria.
Exploration of the Interventricular and Interatrial Septa, their roles in separating heart chambers.
Detailed anatomy of the right atrium, including its walls and the function of the pectinate muscles.
Description of the right atrium's medial wall, featuring the oval fossa and the coronary sinus.
Explanation of the tricuspid valve's structure and function in preventing backflow of blood.
Anatomy of the right ventricle, highlighting the trabeculae carneae and their role in blood flow.
Function of the pulmonary valve and its similarity to the aortic valve in structure.
Introduction to the left atrium, its position, and the significance of the pulmonary veins.
Detailed look at the left ventricle, including the mitral valve and aortic valve.
Concluding remarks and anticipation for the next video covering the heart wall layers and conducting system.
Transcripts
Hey, What's up. Meditay here. Let's talk about the anatomy of the heart. In this video,
We're first going to look at how the blood circulates in the body.
After that, we're going to cover the different external structures you'll find on the surface
of the heart. Then we're going to open up the heart and go through the internal structures of
each chamber, which include the right and left atrium and the right and left ventricles.
Then in the next video, we'll talk about the layers of the heart's wall,
the conducting system, and then the topography. Now, let's start with the circulation.
So here is see the anterior view of the thorax, right?
If you remove the sternum and the rib cartilage, you'll be able to see the heart
right here. The heart lies between the pleura of the lungs in an area called the mediastinum. Now,
let’s go ahead and pull the heart out. So before we talk about the heart's anatomy,
I wanna first take you through the general layout of the blood circulation in the body.
Once you understand the concept of how the blood circulates in the body, you'll be able to learn
the anatomy of the heart much more efficiently. Ok. Throughout your body, your blood will either
be deoxygenated, meaning it lacks oxygen. And Oxygenated blood that has oxygen.
We’re going to start with the heart receiving deoxygenated blood from the body. So the body
has collected the oxygen, and it's sending the blood back towards the heart. The blood will
enter the heart through the superior and inferior vena cava into the first chamber
which is the right atrium. So the color blue will represent deoxygenated blood.
The blood is then going to go through the tricuspid valve into the right ventricle. The
right ventricle is then going to pump the blood through the pulmonary valve and then into the
pulmonary artery, which is then going to pump the blood to the lungs to exchange CO2 with Oxygen.
And when this is done, blood will come back into the heart with oxygen, so the blood is oxygenated,
now represented in red. And they will come back through the pulmonary veins into the left atrium.
The circulation where the blood goes from the heart to the lungs and back
is called Pulmonary Circulation or the small circulation since it’s a circuit on its own.
Now, the left atrium will send the blood through the bicuspid valve towards the left ventricle. And
when the left ventricle pump, it'll send the blood through the aortic valve where it's eventually
going in end up in the aorta and then back to the body again. So the circulation in which the left
ventricle pumps blood to the body, and the body sends the blood back into the heart is called the
Systemic Circulation, or the major circulation. And notice that in the pulmonary circulation,
Arteries contain blood without oxygen, and veins contain blood with oxygen. Opposite from the
systemic circulation, where arteries contain blood with oxygen and veins contain deoxygenated blood.
Awesome. Let's finally start with the actual anatomy.
So if we turn this picture to the side, you’ll be able to see
a pointy end called the Apex of the Heart, Which is directed forward and downwards to the left.
And then if we turn the heart around and look at the backside. We can see the heart's base,
or basis cordis, directed backward and a little to the right. The base is connected with the
great vessels you see here. So an apex and a base. Now the heart has three surfaces; it has Pulmonary
Surface, towards the left lung, as you see here. And then, we also have the Sternocostal Surface
directed towards the inner surface of the ribs and the perfectly drawn sternum.
And then, we have the Diaphragmatic Surface towards the central tendinous part of the
diaphragm. Some sources say there are 5 surfaces on the heart. Counting the
right pulmonary surface and the base as two other surfaces, so sources may vary.
Let's now take a closer look at the surface. The only margin that the heart has
is the right margin or the right border, which lies between the Sternocostal Surface
and the Diaphragmatic Surface. One cool thing in knowing the
external structures of the heart is that you’re actually able to know exactly where the inner
chambers are based on the external structures. And I’ll show you how. First, we have the Coronary
Sulcus, which separates the ventricles from the Atria. This sulcus goes around, and here you
see the posterior aspect of the heart again. The Coronary Sulcus goes all the way around like this
separating the right and left atrium from the right and left ventricles.
Another sulcus you’ll be able to see is the Anterior Interventricular Sulcus.
This sulcus continues posteriorly as the posterior interventricular sulcus,
and it separates the right ventricle from the left ventricles externally.
Now. Let’s take the heart and give it a good slice, then remove the upper half,
and look at it from this perspective. You’ll see that it looks like this.
So we have this wall called the Septum of the Heart separating the right side of the heart
from the heart's left side. And it's crucial to have this wall because remember the right side of
the heart contains blood without oxygen, while the left side of the heart contains blood with oxygen,
and you really don't mix those up, so it’s good to have this wall.
Alright, so we divide this wall into two parts. We first have the Interventricular Septum,
separating the two ventricles. And we have the Interatrial Septum, separating the two atria.
Now the Interventricular septum can be further subdivided into two parts. We have the muscularis
part down here since, in this area, the muscles are packed together. And up here is the membranous
part, since this is the area where the valves are. So that's mainly the general structures we have
on the external heart. Now, let's look detailed into the different chambers.
We'll start with the right atrium. So here you see the anterior lateral view of the heart.
And the right atrium is located right about here inside this area. In order to understand the full
anatomy of the right atrium, we need to go through all six walls of it. So let’s work our way through
this list, starting with the Anterior Wall. So the Anterior Wall is right here,
and it consists of the Right Auricle. The Right Auricle is a small muscle pouch,
and this is where the Anterior and Lateral Wall has something in common. Both have this muscle
layer called Pectinate Muscle. As you see here, the pectinate muscle consists of striated muscle
fibers, which help contract the right atrium to push the blood further into the right ventricle.
That's the anterior and lateral walls so let's check them.
Now, let’s go ahead and remove the lateral and the anterior wall to look inside the
right atrium. Here we can see a little bit of pectinate muscle we mentioned earlier. Now,
if you look at the superior wall, the superior wall has an opening for the Superior Vena cava.
So That's mainly the superior wall. On the posterior wall,
we can find the opening for the inferior vena cava. Remember, the heart is tilted forward,
and because it’s tilted forward, the inferior vena cava becomes part of the posterior wall.
Another thing you’ll find in the posterior wall is,
You know, anteriorly, you have the rough pectinati muscle, right? But posteriorly,
between the opening for the superior and inferior vena cava, we have a wall called the Sinus of Vena
Cava or the sinus venarum. This had a function during embryonic development, but now it forms the
area for the SA node, for the conductive system. Now, there's a line that separates the pectinate
muscle and the sinus venarum. If we look at the outside of the lateral wall again,
we have a crest called the terminal crest that separates the transition between the
pectinate muscle and the sinus venarum. So that's mainly how we can distinguish
where the sinus venarum is and where the pectinate muscle ends.
On the posterior wall, we can also see a valve. And this valve is called the valve
for the inferior vena cava. It’s considered an embryonic valve that, during fetal life,
the blood went directly from the inferior vena cava to a hole on the medial wall, which is now
called the Oval Fossa. The blood went directly from the right atrium to the left atrium since the
fetus doesn’t need pulmonary circulation because they get their oxygen through the placenta. But in
adults, the valve remains, it’s still there, but it remains as small folds on the posterior medial
wall, which is that ridge you see here. So that is the posterior wall.
Now let’s do the medial wall. Remember, the medial wall is made up of the septum between
the right and left atria. Called the Interatrial Septum. On this septum, that’s where you'll find
the oval fossa. And Around the oval fossa, you’ll see that it’s bordered by an elevation
called border of oval fossa, also referred to as the limbus of oval fossa.
Another thing you’ll find here is an opening for the coronary sinus, which lies between the
medial and posterior wall. This is the opening of the main vein draining blood from the heart.
And this opening is guarded by a valve called The Valve for the coronary sinus.
Which is really just a fold covering it. So on the medial wall of the heart,
you will also find very small openings returning blood directly from the layers of the heart's wall
called the openings of the smallest cardiac veins. So that's mainly the structures on the medial
wall. Now lastly, we have an inferior wall. And to see this one, we need to slightly change the
angle, as you see here. Now you’re able to see an opening called the right atrioventricular orifice
or opening. That's the opening between the right atrium and the right ventricle. And this opening
is guarded by a tricuspid valve, which prevents the backflow of the blood. It's called a tricuspid
valve because it has three cusps or three leaflets. So if we zoom in on it, you'll see three
cusps right here—just a quick way to remember that the tricuspid valve lies on the right side.
The name tricuspid valve has the letters "R" "I," which resembles the word right, so the tricuspid
valve is on the right side. And it consists of the anterior, posterior, and the septal cusps
So that is the inferior wall. Now, let's look at the right ventricle. So the right ventricle
has a triangle shape, as you see here. Now on the base of the right ventricle,
you'll find the Right Atrioventricular Opening, which is the opening between the right atrium
and ventricle. Another opening you'll find is the Opening for the Pulmonary Trunk.
Now, If you look within the actual ventricle, you'll see a rough inner layer, right?
And most of that rough inner layer is called Trabeculae carneae. The Trabeculae are essential
because they prevent the blood from swirling around cuz remember, when the blood enters
the heart, it enters with high velocity. And by having this rough inner layer,
you actually prevent the blood from getting air bubbles as they reach a sudden break
which could cause a potential air embolism And here, you can also find papillary muscles,
just like in the atria. Their function is connected to the tricuspid valve. So this
valve again guards the right atrioventricular opening and has three cusps or leaflets, as I
mentioned earlier. It has the anterior cusp right here, and it has a posterior cusp and has a septal
cusp towards the ventricular septum. That's a septum that divides the right and left ventricle.
These cusps, including all other cusps, are formed by the endocardium. We’ll talk more about
that in the next video but keep that in mind. The opening is also surrounded by a fibrous ring
that supports the valve and functions as an attachment point for these three cusps.
So each cusp has 3 margins. One margin of each cusp is attached to the fibrous ring.
And the other two margins are attached to the Tendinous Chords, which are cords of fibers
that attach the cusps to the papillary muscles, which control the valves' opening and closure.
And then up here, we have something called the pulmonary valve, which has 3 semilunar cusps.
And these, just like the tricuspid valve, are formed by a double layer
of the endocardium. If you’re unsure what endocardium is, that's no problem. For now,
just know that the endocardium form these cusps. The pulmonary valve also has a fibrous ring around
where the base of the semilunar cusps are attached to. While the free margins are directed upwards
into the pulmonary artery, as you see here. The pulmonary cusps have a free margin,
as you see here, so they differ from the tricuspid valve. There’s a nodule in the center of the free
borders called Nodules of the semilunar valve, which provides a tight closure of the valves.
And so here we can see another structure Between the semilunar valves and the walls of
the pulmonary artery. We can see the sinuses called the sinus of the pulmonary trunk.
The pulmonary trunk is just another name for the pulmonary artery, and this sinus is basically just
a space here that the cusps form. Here's another picture just to visualize it. You can see the 3
semilunar cusp down here, and you have a nodule in the middle which helps with the tight closure,
and the space or the depression behind it's called the pulmonary sinus.
So that was the anatomy of the right side of the heart. Here again, you get the blood coming from
the body into the right atrium. From the right atrium, blood goes through the tricuspid valve,
as you see here, into the right ventricle. Then the blood continues up through the pulmonary
valve into the pulmonary artery. Which goes to the lungs, where it gets oxygenated, and then
the oxygenated blood goes into the left atrium. So now, let's have a look at the walls of
the left atrium. Remember, the left atrium lies on the other side of the right atrium.
Let’s repeat something first. So here you see an anterior view of the heart,
where you’ll be able to see the right atrium again. Remember, the anterior wall of the
right atrium consists of the right auricle. But if you turn the heart so that we're looking at
the posterior lateral surface. We can see that the anterior wall here is made up of the left auricle,
which remember is a muscle pouch containing pectinate muscle.
And back here, we can find 4 blood vessels on the posterior wall where oxygenated blood
from the lungs comes in. These blood vessels are called Pulmonary veins. So the posterior
wall of the left atrium has four openings, called the Openings of the Pulmonary Veins.
Alright, so let's open up the walls and look at the inside. You can see that the medial wall is
the Interatrial Septum, which, as you know, separates both Atria. And then, anteriorly,
you'll find the opening, which leads into the left ventricle, The Left Atrioventricular Opening.
And this opening is also guarded by a valve called the bicuspid valve, or you can also use the term
mitral valve. So that was all for the left atrium, now. Let's look at the left ventricle.
Here you see the left ventricle with the mitral valve. And if we tilt it a little bit in this
direction, you will see one more valve. So let's now talk about the base of the left ventricle.
From these two angles, we're able to see the Left Atrioventricular Opening,
where blood from the left atrium comes in, and the Aortic Opening, which leads into the aorta.
Let's now do the Left Atrioventricular opening first and then do the Aortic Opening. Here you see
the Left Atrioventricular Opening again, and it's guarded by the bicuspid valve or the mitral valve.
And you know, just like the other valves, it has a fibrous ring around that the cusps are
attached to. Now since it’s called Bicuspid valve, it means that this valve consists of two leaflets.
One is called the Anterior Cusp, and one is called Posterior Cusp.
But regardless of the name, there're actually several small cusps located in between them.
So here we have the bicuspid valve. Here's the anterior cusp and here the posterior cusp.
And these small cusps right here, these are called commissural cusps, Which are very small
cusps that support the valve. Now If you look closely at the surface of the left ventricle,
you'll notice that it more or less has the same structures as the right ventricle.
There's the Trabecula Carneae for the blood flow. And here we have Papillary Muscles,
which remember are attached to the Tendinous Chords. So the Tendinous Chords bind the
cusps of the mitral valve onto the papillary muscles. So when the papillary muscles contract,
they open up the mitral valve. Now, let’s turn the heart in this direction so
that we can see the aortic opening. This region that leads into the aortic opening is called
the Aortic Vestibule inside the left ventricle. So this opening is guarded by the Aortic Valva,
which is made up of three semilunar cusps, very similar to the pulmonary valve. Here we’ll find
three semilunar cusps, but this time, they’re called the Right semilunar cusp, the posterior
semilunar cusp, and the Left semilunar cusp. So right posterior left. They also have
nodules that help close the valve tightly. We also have 3 aortic sinuses here on the top,
which remember are just a depression formed by the semilunar valve.
Awesome. So now we have gone through the pulmonary circulation,
which pumps oxygenated blood into the left atrium. The left atrium will now pump the blood through
the bicuspid valve into the left ventricle, which will pump blood through the aortic valve
into the Aorta. And then to the rest of the body. I really hope you found this video helpful. If it
did, please like, comment, share. Now in the next video, we'll look at the layers of the heart wall,
the conducting system, and then the topography of the heart.
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