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Overview of the veins of the vertebral column and the vertebral canal.
Hey everyone! It’s Nicole from Kenhub, and in this tutorial, we're going to be talking about the veins of the vertebral column.
The vertebral column is a structure made up of thirty-three vertebrae which are joined by a complex system of ligaments. It provides structure for the body and protects the spinal cord. First of all, in this tutorial, let’s just briefly look at some of the key features of the vertebrae in order to have a general idea where the veins of the vertebrae are located in this tutorial.
So a single vertebra can be divided mainly into the body, the transverse process and the spinous process where the spinous process faces posteriorly. This foramen in the middle is called the vertebral foramen which forms the vertebral canal through which the spinal cord passes. And each vertebra is supported by a cartilaginous intervertebral disc which acts like a cushion to absorb any mechanical stress exerted onto the vertebral column.
So now that we’ve gone over the key anatomy features of the vertebra, let’s now start looking at the venous drainage of the vertebral column.
So, as we all know, the vertebral column is drained by venous plexuses which are otherwise known as a network of veins. The venous plexuses which drain the vertebral column are formed by the spinal veins along the vertebral column both inside and outside the vertebral canal and these plexuses are appropriately named the internal and external vertebral venous plexuses.
Let’s first have a look at the internal vertebral venous plexus which is also known as the epidural venous plexus. This illustration that we’re looking at shows the lateral view of the vertebral column which is being cut along the sagittal axis. The internal vertebral venous plexus is divided into the anterior and posterior vertebral plexus which is found within the vertebral canal. The anterior and the posterior vertebral plexuses communicate with the external vertebral plexus which we’ll talk about later in the video.
Radicular veins and the basivertebral veins all join the internal vertebral venous plexuses and drain the vertebral column.
Here we see the anterior internal venous plexus highlighted in green, and you can see that it lies on the posterior surfaces of the vertebral bodies within the vertebral foramen. And this ligament that you can see on the image is the posterior longitudinal ligament that holds the vertebrae. The posterior internal vertebral venous plexus is found on either side of the midline in front of the vertebral arches and anastomosis with the posterior external plexus. And the anterior and the posterior internal venous plexuses communicate with each other through a complex network of venous branches.
So moving onto the external vertebral venous plexus which as you can see communicates with the internal vertebral venous plexuses through the intervertebral foramina. The external vertebral venous plexus also divides into the anterior and posterior external vertebral venous plexuses. It surrounds the vertebral column and, in addition, it will form several connections with the azygos, the lumbar and the deep cervical veins.
Alright, here, we can see the anterior external vertebral venous plexus which lies along the front of the body of the vertebra and it communicates with the basivertebral veins seen here within the vertebral body and the intervertebral veins. The posterior external vertebral venous plexus seen here is found along the posterior surfaces of the vertebral arches and the spinous processes of the vertebrae. Both the anterior and the posterior external vertebral venous plexuses anastomose with the vertebral, occipital, and deep cervical veins.
So, another main group of veins that drain the vertebral column that I want to talk about today are the intervertebral veins. And as you can see, they run alongside these spinal nerves through the intervertebral foramen and drain the internal and external vertebral venous plexuses forming a communication between the two plexuses.
Alright, another set of veins I want to talk about are some veins that run within the body of the vertebral column, and these are called the basivertebral veins. And here in this illustration, you can see the basivertebral veins highlighted in green and they originate from the foramina on the posterior surfaces of the vertebral bodies and communicate through small openings.
Basivertebral veins are drained posteriorly by the anterior internal vertebral venous plexus and anteriorly by the external vertebral venous plexus. So this vein that you see running up along the side of the vertebra is the ascending lumbar vein, and as the name indicates, it runs up through the lumbar region of the vertebral column.
So as you can see, the ascending lumbar vein is a paired structure comprising of right and left ascending lumbar veins. It starts at the lateral sacral veins and as you can see, it runs superiorly. So, when the ascending lumbar vein crosses the subcostal vein, the right ascending lumbar vein becomes the azygos vein and the left ascending lumbar vein becomes the hemiazygos vein.
Okay now that we’re finished talking about the veins, I want to talk a little bit about some clinical notes regarding these veins. And the vertebral veins are significant in that they have no valves which makes them more susceptible to distention due to increased intrathoracic or intra-abdominal pressure. For example in patients with ascites which if you may remember, is when there’s a buildup of fluid in the abdomen, and this often occurs with liver disease or sometimes during pregnancy. An ascites can lead to an increased risk of trauma during certain clinical procedures, for example, when we want to place a needle into the epidural space as we often do when someone is giving birth.
Alright, let’s now summarize what we’ve gone through in this video. So, first, we had a brief look at the basic anatomical features of a vertebra which can be divided into a body, a spinous process and a transverse process. The main veins that drain the vertebral column are the internal and external vertebral venous plexuses and the intervertebral veins, which form a complex network.
The internal and external vertebral venous plexuses are further divided into anterior and posterior parts. And other veins, such as the paired ascending lumbar veins are found along the side of the spine and the basivertebral veins that run within the body of the vertebrae also drain the vertebral column.
And that’s it for today. Thanks for watching!