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Arteries and veins of the spinal cord.
Hi everyone! This is Megan from Kenhub, and welcome to another anatomy tutorial. In today's tutorial, we're going to be covering the blood vessels of the spinal cord, specifically, the arteries, veins and plexuses that supply and drain the spinal cord.
Before we begin this tutorial, I'm just gonna give you a quick overview of some components of the spinal cord. So, here, we can see the grey matter of the spinal cord and the white matter of the spinal cord. Here we have the anterior horn, the lateral horn, and the posterior horn with the central grey matter and here we have the anterior funiculus, the lateral funiculus, and the posterior funiculus.
So, let's begin by looking at these two views of the spinal cord. The first is a posterior cervical view while the second is a frontal view at the level of the thorax. You may observe in both images that the spinal cord is surrounded by a complex arterial plexus. We will learn to recognize the discrete vascular elements of this plexus later in this tutorial.
For now observe that this plexus is created mainly by the spinal branches of the vertebral arteries. As you can see, there is also a minor contribution of the posterior intercostal arteries, again, via the spinal branches. In a similar fashion, lumbar and sacral arteries contribute to the formation of the spinal arterial plexus in the lower spinal segments. You can see that the posterior intercostal artery has a complicated branching pattern. We will have to clarify this pattern before moving on to learning the discrete elements of the arterial plexus that surround the spinal cord.
There are eleven pairs of intercostal arteries present on the left and right side. The first two posterior intercostal arteries arise from the superior intercostal artery, a branch of the subclavian artery. The remaining nine posterior intercostal arteries arise from the thoracic aorta, as this major artery descends from the thorax to the abdomen directly in front of the spinal cord.
The posterior intercostal arteries are divided into a ventral branch and a dorsal branch. In this image, we can see an example of a ventral branch here. It's located inferior to the rib and superior to the intercostal nerve. Then we have the dorsal branch here which is running posterior to pierce the rostral musculature and irrigate the muscles and skin of the back. Lumbar arteries also originate from the aorta from its abdominal segment while sacral arteries usually emerge from the common iliac arteries.
The dorsal branch of the posterior intercostal arteries further divides into a lateral cutaneous branch and a medial cutaneous branch. In this tutorial, we are ultimately interested in the spinal branch of the dorsal segment of the posterior intercostal artery.
Now that we've clarified the branches of the posterior intercostal artery, we're ready to move on to learn about the spinal arterial plexus. First, we'll look at the radicular arteries. Observe that there are both anterior radicular arteries and posterior radicular arteries, and remember that they arise directly from the spinal branches of the vertebral, posterior intercostal, lumbar and sacral arteries. Though most of these vessels end up supplying either the anterior or posterior nerve roots and the horns of the spinal cord, a minority called the segmental arteries serve to reinforce the anterior and posterior segment of the vascular plexus surrounding the spinal cord. We will talk about the major vessels of the plexus later in this tutorial.
So, let's focus on the radicular arteries. They supply the dorsal and ventral roots of the spinal cord and the peripheral portions of the anterior and posterior horn. In our illustration, we see the anterior radicular arteries which supply the ventral root of the spinal cord and the peripheral portions of the anterior horn of the spinal cords specifically.
The largest anterior radicular artery is also known as the artery of Adamkiewicz. It is usually found in the upper lumbar region arising from between L1 and L2. The artery of Adamkiewicz can be considered as segmental artery because it mainly supplies the lower segments of the spinal cord. In the next image, we can see a frontal view of this artery at the level of the thorax.
In the previous slide, we saw the anterior radicular arteries and, as I've already mentioned, the radicular arteries have both an anterior and posterior division. Here, we can see the posterior radicular arteries which, in the same way as the anterior radicular arteries, arise from the spinal branches of the vertebral, cervical, deep cervical, intercostal, lumbar and sacral arteries. The posterior radicular arteries supply the dorsal root and the peripheral portions of the posterior horn of the spinal cord.
Now that we've covered the radicular and segmental arteries, we can further move on to the arterial plexus they form which spans the spinal subarachnoid space. This plexus, also known as the arterial vasocorona, is found in the innermost layer of the meninges that invests the spinal cord to the pia mater and it supplies the marginal zone of the anterior lateral funiculus. You can see the minor vessels of this plexus highlighted in green in this image.
Now, let's move on to the major vessels. The anterior spinal artery is an unpaired artery that runs along the anterior median fissure of the spinal cord. It arises intracranially along with the posterior spinal arteries from the vertebral artery. Initially, the anterior spinal artery arises bilaterally as two branches of the vertebral artery but the two counterparts fuse at the level of the foramen magnum to form a single trunk that descends along the front of the spinal cord running along the median fissure. The blood received from the vertebral artery suffices only for the cervical segments of the spinal cord. The rest of the anterior spinal artery running down the length of the spinal cord is supplied by the radicular arteries.
The anterior spinal artery gives off several small branches into the anterior sulcus along its course down the spinal cord. These small branches are known as the sulco-commissural arteries. Another interesting characteristic of the anterior spinal artery is that its diameter widens at the level of the cervical and lumbar enlargements. Here, we have a frontal view of this artery at the thoracic level. In the next slide, we can see the sulcal arteries highlighted in green which supply the anterior two-thirds of the spinal cord. They arise from the anterior spinal artery penetrating through the anterior median fissure.
Next, we'll be looking at the left posterior spinal artery and the right posterior spinal artery. These paired posterior branches arise from the vertebral artery – one on the left and one on the right. The left and right posterior spinal arteries supply the posterior funiculi and the remaining parts of the posterior horns of the spinal cord. Occasionally, posterior spinal arteries branch off the posterior inferior cerebellar arteries of the vertebral arteries instead of its main arterial stem.
So, before we move on to the veins, I would like to show you which specific regions of the spinal cord are supplied by the anterior and posterior spinal arteries. In this image, we can see the unpaired anterior spinal artery. It supplies regions of grey matter such as the anterior horn, the lateral horn, and the central grey matter. It also supplies the anterior portion of the posterior horn. It supplies regions of white matter such as the anterior funiculus and the lateral funiculus. Here, we can see the two posterior spinal branches which supply the posterior horn of the grey matter and the posterior funiculus of the white matter.
So far, we've covered the arteries that supply oxygenated blood to the spinal cord and some of their branches. Now, let's look at the venous system that drains it starting with the venous plexus which we see here highlighted in green. This internal vertebral venous plexus drains blood from the medullary capillaries and is further drained by a plexus of surface veins – the coronal venous plexus. The coronal plexus is drained by the sulcal veins which you can see highlighted in green here. The sulcal veins then drain into either the anterior spinal vein or the posterior spinal vein. The plexus is also drained by the anterior and posterior radicular veins which we can see here.
Now, let's take a closer look at these veins. You may have noticed that the venous plexus follows a pattern similar to the arterial plexus. There's an anterior spinal vein, but unlike what we saw in the arterial network which features two posterior spinal arteries, there is only a single posterior spinal vein. In this illustration, we can see the anterior spinal vein. The anterior spinal vein runs longitudinally along the length of the spinal cord and provides venous drainage for the anterior part of the spinal cord. It receives blood from the sulcal veins and drains into the anterior radicular veins.
The venous system of the posterior spinal cord differs from the arterial system in that only a single major vein – the posterior spinal vein – forms along the midline of the posterior spinal cord. So, as I said previously, note that while there are two posterior spinal arteries, there is only one posterior spinal vein. Here, in this illustration, you can see the posterior spinal vein highlighted in green. The posterior spinal vein receives venous drainage from the posterior part of the spinal cord via the sulcal veins and drains into the posterior radicular veins.
And, finally, the last pair of veins that drains the spinal cord are the anterior and posterior radicular veins seen here highlighted in green. There are twelve pairs of anterior and posterior radicular veins that receive tributaries from the anterior and posterior spinal veins. The anterior radicular veins – as you can see in this illustration – join with small veins of the venous plexus and with the posterior radicular veins to form the intervertebral veins. Finally, these veins which are seen here together with the spinal nerve pass through the intervertebral foramina into the vertebral, posterior intercostal, lumbar and lateral sacral veins.
Now that you just completed this video tutorial, then it’s time for you to continue your learning experience by testing and also applying your knowledge. There are three ways you can do so here at Kenhub. The first one is by clicking on our “start training” button, the second one is by browsing through our related articles library, and the third one is by checking out our atlas.
Now, good luck everyone, and I will see you next time.