In this video, we're going to talk about the types of blood vessel anastomoses. So really there are 3 main types of blood vessel anastomoses that we have numbered down below in our text 1, 2, and 3. And these are the arterial anastomoses, the venous anastomoses, and the arteriovenous anastomoses. And so notice that down below in the image, we have a section for each of these three types.

Now the arterial anastomoses, as its name implies with the term arterial, are going to be convergence or merging points of arteries, which recall carry blood away from the heart. And so these arterial anastomoses are commonly found in joints such as the elbow joint and the knee joint, for example, where movements such as extreme flexion, for example, can actually hinder the flow of blood through an artery. And so these arterial anastomoses can help to create collateral channels so that the blood always has an alternative pathway around the joint regardless of what position it's in to ensure that our tissues are always adequately supplied with blood. And, also, these arterial anastomoses are commonly found near vital organs, such as the brain and the heart, for example, where the body really can't afford for the obstruction of a single artery to compromise these tissues. And so arterial anastomoses, once again, are commonly found near these vital organs to help create collateral channels to provide alternative pathways for the blood to flow to these vital organs. So notice down below on the far left side of our image, we have the arterial anastomoses, and notice that it is the same exact image that we showed you in our previous lesson videos of the arterial anastomoses of the elbow. So you can see all of these blood vessels running through and by the elbow joint here and around the elbow joint, and notice, that the arterial anastomoses are being highlighted here in green, and so those are the convergence or the merging points of these arteries, which help to create collateral channels to provide alternative pathways for the blood to flow through or around the elbow joint, regardless of what position the elbow joint is in.

Now the next type of anastomoses that we have here are the venous anastomoses, which as its name implies with the term venous, which means veins, are going to be convergence or merging points of veins, which recall carry blood towards the heart. Now what's really important to note about these venous anastomoses is that they are significantly more common than any other type of anastomosis. And so because these venous anastomoses are so common, they also create lots and lots of collateral channels in the veins. And so, veins have a great amount of collateral circulation in comparison to arteries. And because that's the case, generally, the blockage of a single vein is considered far less life-threatening than the blockage of an artery. And, again, that has to do with the fact that these anastomoses are significantly more common, providing significantly more collateral channels in veins. Now, down below in the image in the middle, we're showing you examples of venous anastomoses. Now, veins typically run closer towards the surface of the skin, so you can see actually on the back of the person's hand here, all of these merging and converging veins here on the back of this person's hand, showing you those venous anastomoses and how common they are.

Now, last but not least, we have the arteriovenous anastomoses, which, as its name implies, it has a little bit of that arteriole root, and it also has a little bit of the venous root here. And so it is really exactly what it sounds like. These are going to be convergence or merging points of arteries directly into veins, essentially bypassing the capillaries. Now this bypassing of the capillaries might sound a little bit familiar to you because recall when we talked about the capillary bed structure of the mesenteries in our previous lesson videos, which recall are the serous membranes of the digestive system, that we did talk a little bit about the bypassing of capillaries. And so, it turns out that the vascular shunt of the mesenteries is an example of an arteriovenous anastomosis. And so these arteriovenous anastomoses are common in the mesenteries, but also common in areas such as the skin, fingers, toes, and ears, and this is really all to more precisely reroute blood flow, giving our bodies the ability to redirect blood flow to other areas of the body when needed. And so notice down below, over here on the far right of our image, we're showing you an example of arteriovenous anastomosis. And so, again, this top section of the image should look really familiar to you from the capillary bed structure of the mesenteries that we covered in our previous lesson videos. But notice here that this vascular shunt that I'm highlighting here in green is an example of an arteriovenous anastomosis because it connects this arteriole over here directly to the venule over here, bypassing the capillaries that you see here since these precapillary sphincters are constricted. But notice that down below, right here, we're showing you yet another example of an arteriovenous anastomosis, which is very similar to a vascular shunt, except there are no capillaries being shown here at all. And so that's also totally a possibility for arteriovenous anastomoses. And again, these arteriovenous anastomoses are important for helping to reroute blood flow. And so the rerouting of the blood flow really does make a lot of these organs more susceptible to frostbite because, under cold conditions, the blood is going to be rerouted away from the skin, fingers, toes, and ears, to ensure that the blood is rerouted to vital organs, during cold conditions. So that's really what makes these areas of the body here more susceptible to frostbite under cold conditions, due to these arteriovenous anastomoses. And so really, this here concludes our lesson on the types of anastomoses, and moving forward, we'll be able to apply these concepts and continue to learn more. So I'll see you all in our next video.