Description

This video covers the Superior Vena Cava, Azygos Vein, Right and Left Brachiocephalic Veins, and their tributaries, with anatomical details and clinical relevance.

Superior Vena Cava (V. Cava Superior)

• Short Vein with a large diameter (2-3 cm).
• No valves.

Azygos Vein (V. Azygos)

• Unpaired vein located behind the Inferior Vena Cava, on the right side of the vertebral column.
• Receives blood from the Right Ascending Lumbar Vein (V. Lumbalis Ascendens Dexter).
• May function as portocaval and cavo-caval anastomoses.

Tributaries of Azygos Vein:

• Visceral Tributaries:
  • Esophageal Veins (Vv. Oesophageales).
  • Bronchial Veins (Vv. Bronchiales).
  • Pericardial Veins (Vv. Pericardiacae).
  • Mediastinal Veins (Vv. Mediastinales).
• Parietal Tributaries:
  • Hemiazygos Vein (V. Hemiazygos).
    • Accessory Hemiazygos Vein (V. Hemiazygos Accessoria).
  • Right Superior Intercostal Veins (Vv. Intercostales Superior Dextrae).
  • Right Posterior Intercostal Veins (Vv. Intercostales Posteriores Dexter).
  • Superior Phrenic Vein (Vv. Phrenicae Superiores).

Left Thoracic Veins:

• Left Posterior Intercostal Veins (Vv. Intercostales Posteriores Sinistrae), draining into the Accessory Hemiazygos Vein and the Hemiazygos Vein.

Right Brachiocephalic Vein (V. Brachiocephalica Dexter)

• Formed by the union of the Subclavian Vein (V. Subclavia) and the Internal Jugular Vein (V. Jugularis Interna).
• Approximately 3 cm long.

Tributaries of the Right Brachiocephalic Vein:

• Right Vertebral Vein (V. Vertebralis).
• Right Inferior Thyroid Vein (V. Thyroidea Inferior Dexter).
• Right Internal Thoracic Vein (V. Thoracica Interna Dexter).
  • Anterior Intercostal Veins (Vv. Intercostales Anteriores) communicate with the posterior intercostal veins.
  • Musculophrenic Vein (V. Musculophrenica).
  • Superior Epigastric Vein (V. Epigastrica Superior).
• Right Supreme Intercostal Vein (V. Intercostalis Suprema).

Left Brachiocephalic Vein (V. Brachiocephalica Sinister)

• Approximately 6 cm long.

Tributaries of the Left Brachiocephalic Vein:

• Left Vertebral Vein (V. Vertebralis Sinister).
• Left Inferior Thyroid Vein (V. Thyroidea Inferior Sinister).
• Left Internal Thoracic Vein (V. Thoracica Interna Sinister).
• Left Supreme Intercostal Vein (V. Intercostalis Suprema Sinister).
• Left Superior Intercostal Vein (V. Intercostalis Superior Sinistra).
• Thymic Veins (Vv. Thymicae).
• Pericardiophrenic Veins (V. Pericardiophrenicae).

Clinical Relevance:

• Superior Vena Cava Syndrome (SVCS): Compression or obstruction of the SVC leads to venous congestion, facial swelling, and distended neck veins.
• Azygos System as a Collateral Pathway: Can compensate for venous return when the IVC or SVC is obstructed.
• Portocaval Anastomoses: In cases of portal hypertension, azygos tributaries may enlarge, causing esophageal varices.

Sources Used:

• Memorix Anatomy (2nd Edition) – Hudák Radovan, Kachlík David, Volný Ondřej.
• Complete Anatomy by 3D4Medical.
• Biorender.
• University Notes and Lectures.

Transcript

Introduction
0:03
Let’s now talk about the superior vena cava and its associated veins.
0:07
So in this video, we’re first going to talk briefly about the superior vena cava,
0:12
We’ll talk a little bit about the azygos vein Then we’ll cover the hemiazygos vein and the
0:17
accessory hemiazygos vein After that, we’ll talk about the right and
0:21
the left brachiocephalic veins.
0:23
We’ll go through their characteristics, their tributaries and what structures they all generally
0:28
drain.
Veins of the Systemic Circulation
0:29
Awesome So, the easiest way to understand the veins
0:33
of the systemic circulation is to divide them into their own systems.
0:37
So the veins of the heart form their own system We have the Veins of the Inferior Vena Cava,
0:43
which is responsible for supplying the lower half of the body
0:46
Veins of the superior vena cava for the upper half of the body
0:50
And the portal system, which drains nutrients from the intestines
0:53
and waste products from the spleen and dumps them into the liver to be processed,
0:58
which then lead the blood into the inferior vena cava again.
1:01
So these are the 4 main systems of veins we have in our bodies.
Superior Vena Cava
1:05
Let’s now talk briefly about the superior vena cava and it’s associated veins.
1:10
The superior vena cava is a short vein as you see here,
1:14
And it has a quite large diameter.
1:16
Approximately 2-3 cm wide It carries deoxygenated blood from the upper
1:21
half of the body, so the head, neck, upper limbs, thorax, and upper part of the back.
1:27
Then it descends vertically to empty into the right atrium at the level of the third
Azygos & Hemiazygos Vein
1:32
sternocostal joint.
1:34
So that was mainly everything for the superior vena cava.
1:38
Now let’s talk about the azygos vein, which is a vein that drains into the superior vena
1:43
cava.
1:44
The Azygos vein is located very close to the vertebra, behind the inferior vena cava.
1:50
So if we cut through the inferior vena cava, We’ll be able to see the azygos vein here
1:55
very clearly.
1:56
Ok, so where does it get its blood from?
1:59
Well, here you see the common iliac vein.
2:03
The common iliac vein has a tributary called the right ascending lumbar vein,
2:08
And this vein becomes the Azygos vein at around the 12th thoracic vertebra.
2:14
And as the azygos vein ascends along the right side of the vertebral column.
2:19
It arches anteriorly at the level of T4, to then empty into the Superior Vena Cava.
2:25
Ok, so here are some fun facts about the azygos vein.
2:28
The Greek root zyg refers to a pair.
2:32
‘A-‘ means not.
2:34
That means a-zygos means unpaired.
2:37
That’s why you’ll find this vein only on the right side of the vertebral column, while
2:42
on the left side you’ll find the hemiazygos and its accessory on the left side of the
2:46
body.
2:47
Kinda makes sense doesn’t it?
2:49
Another thing that’s good to know is that the azygos vein and the hemiazygos vein are
2:53
valveless.
2:54
Usually when you study veins, you’ll see that veins have valves to prevent backflow of blood.
3:00
These two doesn’t have any of these.
3:02
They therefore may function as portocaval and cavo-caval anastomoses.
3:07
Meaning if there’s a liver disease that causes narrowing of the portal vein.
3:11
The blood starts shunting over to other places since it can’t get through the liver.
3:17
So it can go through the esophageal branches of the azygos vein causing esophageal varices
3:23
. But that’s pathology, we’ll cover this in
3:24
the future.
3:25
Alright.
3:26
That was a little fun fact about the ayzygos vein
3:27
So it do have tributaries, or side branches if you may.
3:31
It has visceral tributaries And parietal tributaries.
3:35
Visceral going to organs, parietal going to muscle and bone
3:40
And so I wanna start with this vein right here, called the hemiazygos vein.
3:46
Similar to the azygos vein, the hemiazygos vein also starts from the ascending lumbar
3:51
vein, but the left one this time, at around T12.
3:54
And it empties into the azygos vein at around T8 to T9.
3:59
We have the accessory hemiazygos vein a little higher up, which receives blood from the left
4:04
4-7th intercostal veins.
4:07
These veins vary a lot between people.
4:09
It can either anastomose with the left superior intercostal veins of the left brachiocephalic
4:14
vein, or not.
4:16
It can just start from the 4-7th left intercostal veins as well.
4:20
And in the lower direction; It can either anastomose with the hemiazygos
4:25
vein, or Anastomose with the azygos vein, as you see
4:29
here.
4:30
That’s why I feel like It can be pretty daunting studying veins.
4:32
There are so many variations.
4:33
So that’s these ones.
4:34
Now, let’s add some organs.
4:36
The first visceral tributary of the azygos vein is the oesophageal veins.
4:41
If we go ahead and turn this model to the side,
4:43
We’ll see that both the azygos and hemiazygos veins have tributary veins that drain the
4:49
esophagus.
4:50
And if we go ahead and add the bronchi.
4:52
You’ll see that it also has bronchial veins that drain into the azygos vein
4:57
We have pericardial veins as well, And mediastinal veins, draining various structures
5:02
in the mediastinum like lymph nodes.
5:05
Alright Let’s now add the ribs on the right side.
5:09
The azygos vein has parietal tributary veins called the right superior intercostal veins,
5:16
which drain the 2nd ad 3rd Right intercostal spaces.
5:20
Sometimes the 4th as well.
5:22
It has the right posterior intercostal veins, which drain the lower 8 right intercostal
5:27
spaces.
5:28
Now just to give you a complete picture.
5:30
On the left side.
5:31
Here we have the left posterior intercostal veins, which drain into the accessory and
5:36
the hemiazygos vein.
5:38
Alright.
5:40
Then we have a vein that’s associated with the Diaphragm
5:43
Called the superior phrenic vein.
Brachiocephalic Veins
5:45
Alright!
5:46
That was the azygos and the hemiazygos vein!
5:48
Now.
5:49
As the Superior Vena Cava ascends, it splits into the right and the left brachiocephalic
5:55
veins.
5:56
And these two veins are formed by a union of the
6:00
Subclavian vein, and the Internal Jugular Vein.
6:03
Now let’s zoom in and focus on these two for a minute.
6:07
Even though the right and the left brachiocephalic vein have identical names.
6:12
There are quite a few differences between their tributaries and size.
6:17
Veins are generally very asymmetrical due to their variations.
Right Brachiocephalic Vein
6:21
The right brachiocephalic vein is about 3 cm long, while the left is about 6 cm long.
6:28
Let’s now go through their tributaries.
6:30
The right Brachiocephalic vein receives blood from the right vertebral vein.
6:35
Which goes through the vertebral transverse foramina, as you see here.
6:39
So what it does is that it drain the external and internal vertebral venous plexuses and
6:45
the deep muscles of the back in the neck region.
6:49
It collects all of that blood; then it goes down through the transverse foramina together
6:54
with the vertebral artery and then opens into the right brachiocephalic vein.
6:58
Next, we have the Right Inferior Thyroid Vein.
7:03
This vein originates from a glandular venous plexus at the thyroid gland.
7:08
And then it descends and travels superficially to the trachea and inserts into the brachiocephalic
7:15
veins.
7:16
Next we have the Right Internal Thoracic Vein.
7:19
It follows exactly the same path as the internal thoracic artery.
7:24
It will Descend along the anterior wall of the thoracic cavity.
7:27
On its way, it mainly drains the upper 5-6 intercostal spaces.
7:32
And then at the level of the 7th rib, it Receives blood from two veins.
7:37
One of them is the Musculophrenic vein Which receives blood from the lower 5-6 intercostal
7:43
spaces, as the anterior intercostal branches And the other one is the Superior Epigastric
7:50
Vein, which passes the diaphragm at the sternocostal triangle – and communicates with the inferior
7:55
epigastric vein.
7:57
And all of these anterior intercostal veins communicate with the posterior intercostal
8:03
veins we mentioned earlier.
8:06
Alright.
8:07
Next we have the right supreme intercostal vein.
8:10
This one.
8:12
Which drains the upper 1 – 2 intercostal spaces.
8:15
So that was the most important tributaries of the Right brachiocephalic vein.
Left Brachiocephalic Vein
8:19
Now let’s turn this model to the other side and cover the Left brachiocephalic vein!
8:24
The left brachiocephalic vein has more or less the same tributaries as the right one.
8:29
Which is the Left Vertebral Vein Left Inferior Thyroid Vein
8:34
Left Internal Thoracic Vein And the Left Supreme Intercostal Vein.
8:39
But it does have some additional tributaries we should mention here as well.
8:42
And the first one is the left superior intercostal vein which drains the upper 3 – 4 intercostal
8:49
spaces of the left side.
8:51
And then another vein that drains the Thymus called the thymic veins.
8:55
And then there’s the Pericardiophrenic Vein, which drains tributaries from the superior
9:00
diaphragm and pericardium So that was all the veins that I wanted to
9:05
cover in this video The next video is going to be about the veins
9:08
of the upper limb