 Good day everybody. This is Dr. Sanger Sanyal, Professor Department Chair. This is going to be a demonstration of the vertebral artery, transverse foremen, suboccipital triangle, the branches of the vertebral artery. So take a look at the model which I'm holding in front of you. This is an articulated skeleton of the vertebral column. So take a look at these red structures that you see on either side. This is the representation of the vertebral artery. The vertebral artery is a branch from the first part of the subclavian artery on this site. The vertebral artery, the other branches being the internal thoracic and the hierocervical trunk. The vertebral artery has got four parts. The first part, a little bit of that can be seen here, is called the cervical part. This cervical part, it runs in a pyramidal space between the longest collie muscle, which is here and the scalinus anterior muscle, which is on the side, both of them made at an apex. So it runs through that pyramidal space. So that is called the cervical part. Then that is also called V1. Then we have the V2 part, or the vertebral part. This vertebral part enters into the transverse foramen of the cervical vertebra. The transverse foramen of the cervical vertebra is located in the transverse process itself, that's why it's called transverse foramen. It is not present in the C7. It's either small or absent. So it goes through the transverse foramen of C6, 5, 4, 3, 2, 1. So that is called the vertebral part or V2. And then it enters into another place called the suboxibular triangle. And that is called the suboxibular part or V3. And after that, as it pierces through the posterior tlandoccipular membrane, which I should describe just now, it enters through the foramen diagram into the radial cavity and then it becomes known as the intracradiate part. And then it has got certain branches. So these are the four parts. The first part, the V1, it gives only a few muscular branches to the muscles of the neck, the deep muscles of the neck. The V2, the vertebral part, it gives spinal branches, which enters segmentally through the vertebral foramen along with the spinal nerves that you can see here, and it supplies the spinal cord. The V3, the suboxibular part, it again gives muscular branches to the muscles of the suboxibular triangle. And I'm going to demonstrate the suboxibular triangle just now. And then the V4 part, that is the intracradiate part, it gives the posterior inferior cerebellar artery, the two anterior spinal arteries, which unite to form a single anterior spinal, the two posterior spinal arteries, it also gives medullary branches to the medulla oblongata, and it also gives meningeal branches. And then the two of them unite, as you can see here, they run intramedially and unite at the lower end of the pons to form the posterior artery. That is the full course of the vertebral artery. Having mentioned that, now let me mention a few quick points about the transverse foramen and the suboxibular triangle, and then I'll mention a few clinical correlations. If you take a close look, the transverse foramen is located in the transverse process of the cell vertebrate. Transverse foramen has got two limps, an anterior limb and a posterior limb. Anttaria limb is formed from the costal element and it ends in the anterior tube BACKL, and the posterior limb is formed by the transverse element. Both of them are primordial elements and the posterior element ends in the posterior tube BACKL. That anterior tube BACKL gives attachment to the scalaneous anterior muscle, the posterior tube BACKL gives attachment to the scalaneous medius in the posterior muscle and the two cubicles are joined by a transverse bar that is called the cost of transverse bar and you can see that here and the cost of transverse bar is what a flat surface which gives passage to the ventral ramus of this spinal nerve which runs behind the vertebral artery. Dorsal ramus goes behind top of the posterior element so that is the transverse foramen and by the way fourth boundary of the transverse foramen is formed by the pedicle so that is about the transverse foramen transverse area through which this vertebral artery passes. If we do vigorous chiropractic manipulation of the cervical spine and it has been well documented it can produce dissecting aneurysm of the vertebral artery either on one side or both sides and that can produce occlusion and vertebro-pacilar ischemic symptoms. Now let's focus our attention to the suboccipital triangle so this region which I've lifted up here this is the region of the suboccipital triangle. What is the suboccipital triangle? As the term implies it is a very small triangle under the occipital bone so this is the base of the occipital bone and the triangle is located in this region. This suboccipital triangle has got the following boundaries. Most of the boundaries are muscular boundaries therefore we cannot see them in a skeleton but I shall demonstrate them to you. It's a triangular area it's got a supramedial boundary which is formed by the rectus capitus posterior major muscle which is a small muscle under the skull. It's got a supralateral boundary which is formed by the superior bleak of head and it's got an infrolateral boundary which is called the inferior bleak of head so the triangle is located here where my finger is touching. This triangle is roofed over by a muscle of the neck, a deep muscle of the neck called the semi spinalis capitus and the floor of the triangle is formed by a membrane which is actually a continuation of the ligament of flavor. Here it is called the atlantooccipital membrane, the posterior atlantooccipital membrane extends from the posterior atlas to the occipital bone and that is the floor and that floor is pierced by this tree that you can see which I mentioned just a little while back. This is the vertebral artery. The vertebral artery as it passes through the transverse foramen of C1 it makes a backward bend and you can see that backward bend here. Then it passes over the posterior arch of atlas. The posterior arch of atlas also forms part of the floor of the suboccipital triangle and then it pierces through the suboccipital membrane and immediately thereafter it enters into the foramen magnum which you can see here. So these are the boundaries of the suboccipital triangle and that is the importance of the suboccipital triangle and that is why this artery in this region is called the V3 portion is called the suboccipital part and here it supplies the muscles which I described just now. Another content of the suboccipital triangle is a very small nerve called the suboccipital nerve which is the dorsodermis of the C1 spinal nerve which supplies the muscles in that region. So these are the course of the vertebral arteries and finally as I mentioned it enters into the cranial cavity and that we can see here once it enters the vertebral artery it runs intermediately fuses with the opposite side to form the basilar artery and we can see the basilar artery here dividing into the two canal divisions the two posterior cerebral arteries. So this is the full course of the vertebral artery that we have seen in the transverse foramen and the transverse foramen itself and the suboccipital triangle. Thank you very much for watching. Dr. Sanjay Sanyal signing out if you have any questions or comments please put them in the comment section below. Have a nice day.