Anastomoses: Study with Video Lessons, Practice Problems & Examples

Blood vessel anastomoses are crucial for maintaining blood flow, especially when primary vessels are compromised. There are three types: arterial anastomoses, which connect arteries; venous anastomoses, which connect veins and are more common; and arteriovenous anastomoses, which link arteries directly to veins, bypassing capillaries. These structures form collateral channels, ensuring tissues receive adequate blood supply, particularly in joints and vital organs. Terminal blood vessels lack anastomoses, making them more susceptible to tissue death upon obstruction. Understanding these concepts is essential for grasping vascular health and circulation dynamics.

Anastomoses Form Collateral Channels

So now that we've covered the different types of blood vessels in our previous lesson videos, in this video, we're going to focus on blood vessel anastomoses, more specifically, how blood vessel anastomoses can form collateral channels. Collateral channels are alternative pathways for blood to reach its same specific destination, which is very important, especially when a blood vessel becomes compromised due to damage, such as a cut, or due to blockage from a blood clot or the buildup of plaque, for example. When a blood vessel becomes compromised, collateral channels can provide alternative pathways for blood to reach its same specific destination. Usually, the amount of blood supplied by the collateral channels is sufficient to keep the tissue or organ alive until the main pathway that was compromised is restored.

When it comes to collateral channels, it is very important for blood vessels to be able to diverge or branch off from one another. However, when it comes to collateral channels, we do not typically focus on the divergence points of blood vessels. This is because the divergence points of blood vessels do not always form collateral channels. The diverging blood vessels may actually supply completely distinct areas, tissues, or organs. Recall that it's only a collateral channel if the alternative pathway allows for blood to reach its same specific destination. Again, we don't tend to focus on the divergence point of blood vessels when it comes to collateral channels. Instead, we tend to focus on the anastomosis, which is the convergence point or the merging of blood vessels. This is because the anastomosis or the convergence points or the merging of blood vessels are often going to be a component of collateral channels.

Before we continue, let's take a look at our image down below on the left-hand side, which is showing us an analogy. In this analogy, the train that you can see here represents the blood, and the train tracks represent the blood vessels. Notice that this train, the blood here, has a final destination that we're indicating down below. Notice that the main pathway or the main blood vessel that the train usually takes to the final destination is actually compromised. It's being blocked by this fallen tree here. This could represent damage to the blood vessels such as a cut or blockage of the blood vessel from, for example, a blood clot or the buildup of plaque. Thankfully, collateral channels like the one highlighted here can provide an alternative pathway for the blood to reach its same specific final destination.

But again, when it comes to collateral channels, we don't tend to focus on the divergence point because notice that this divergence point up above, the blood vessel is not feeding or supplying blood to the same specific final destination. Down below, although this divergence point is part of the collateral channel, more importantly, this collateral channel is merging and converging with this other blood vessel to form the anastomosis, which we have circled in green here, and we can label this as the anastomosis.

Anastomoses are often components of collateral channels, so this route, this alternative route that you can see highlighted here, is a collateral channel, thanks to the anastomosis for the most part. Although not all collateral channels will have anastomoses, it is possible to form a collateral channel without an anastomosis. For example, imagine that this blood vessel over here just curled around to the final destination without actually merging or converging or forming any anastomoses, yet it's still supplying blood to the same area and is still a collateral channel.

Anastomoses are not a requirement for a collateral channel but are often components of collateral channels, which is why they are important. Over here on the right hand side, what we're showing you are the anastomoses of the elbow. Notice that we're focusing in on the forearm and the arm of this person, and you can see the blood vessels going through the elbow joint and around the elbow joint. It's important to know that this elbow joint has a lot of movement, and when it has extreme flexion, it can bend and compromise some of the blood vessels that are in the elbow joint. It's very important for the elbow to have collateral channels so that whenever a blood vessel is compromised, there are alternative pathways for the blood to reach the forearm and our hand to ensure that those tissues constantly receive the blood that they need regardless of what position our elbow might be in. Anastomoses can help form those collateral channels. Notice that the converging points of the blood vessels are highlighted here in green, providing those alternative pathways to ensure that our tissues are constantly receiving the blood that they need, regardless of what position our elbow is in.

The last point I want to leave you all off with is that an end blood vessel or a terminal blood vessel is a non-anastomosing blood vessel, meaning that these blood vessels do not merge or converge to form anastomoses. What this means is that end or terminal blood vessels do not have collateral channels, so they have very poor collateral circulation. If there is an obstruction of an end or terminal blood vessel, that can result in tissue death, since these end or terminal blood vessels are the only pathways that supply blood to these tissues and organs. Organs such as the kidneys, the spleen, and the retina of our eye are supplied with end or terminal blood vessels, making the obstruction of the arteries going to those organs more susceptible to tissue death upon obstruction.

This concludes our lesson on blood vessel anastomoses and how they can form collateral channels. Moving forward, we'll be able to apply these concepts and continue to learn more about anastomoses. I'll see you all in our next video.

Anastomoses Example 1

So here we have an example problem that asks, during which scenario would anastomosis be the most important? And we've got these 4 potential answer options down below. Now, of course, recall from our last lesson video that anastomoses are the convergence points or the merging points of blood vessels that come together. And recall that anastomoses are often a component of collateral channels, which provide alternative pathways for blood to reach its same destination despite the fact that there could be a compromised blood vessel. And so anastomoses are going to be most important when there's a compromised blood vessel, and it helps to form a collateral channel. And so notice that answer option c says, when there is a blockage in an artery. And, of course, the blockage in an artery would be considered a compromised artery since that would inhibit blood flow through that artery. And so the anastomoses could help to form collateral channels that allow for blood to continue to feed and supply the same specific destination despite the fact that there is a blocked or compromised artery. And so answer option c is going to be the correct and the best answer for this example problem. Now, option a says, when blood oxygen levels are higher than usual, but really this has no connection to the anastomosis, so we can eliminate answer option a. Option b says, during physical exercise, and that could be a potentially correct answer, but the best, and most obvious correct answer is still answer option c. So we always choose the best option amongst all options in multiple-choice problems. And then answer option d says, when the body is at rest. And, again, that really doesn't have a direct correlation to these anastomoses, so we can eliminate answer option d. So again, c here is the best answer. That concludes this problem.

What is the primary function of anastomoses in blood vessels?

• A. Remove impurities from blood.
• B. Regulate oxygen levels in the blood.
• C. Control blood temperature.
• D. Help provide alternate routes for blood flow.

Types of Anastomoses

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.

Anastomoses Example 2

So here we have a true or false example problem, and the statement says that a blockage in a vein is typically more life-threatening than a blockage in an artery. And we've got these 4 potential answer options down below. Now recall from our last lesson video that a blockage in a vein is typically less, not more life-threatening than a blockage in an artery. And so what that means is that this statement as is not true. It is false. So we can eliminate answer option a, which suggests that it is true. And so notice that answer options b, c, and d all start with the word false. Now recall from our last lesson video that the reason that a blockage in a vein is typically less life-threatening than the blockage of an artery is that venous anastomoses are significantly more common than any other type of anastomosis. And so what this means is that having more anastomoses in veins means more collateral channels in veins, and that means more alternative pathways for blood to be able to take in veins. And so that means that the blockage of a vein is going to be less life-threatening because there's usually always going to be another alternative pathway for the blood to be able to take. And so notice that answer option b says false. Blockages in veins tend to be less life-threatening as veins have more anastomoses than arteries. And so option b is going to be the best and the correct answer to this example problem. But let's check c and d just to be sure, and notice option c says false, but then it says that blockages in arteries are more life-threatening because they contain more blood. But recall that the lumens of veins are larger than the lumens of arteries, and that allows veins to hold larger volumes of blood. And at any given time, most of the blood in our body is found in veins. And so, arteries don't contain more blood than veins. So for that reason, we can eliminate answer option c. And then answer option d says that, false, but then it says that blockages in arteries are more life-threatening because they have lower blood pressure. But we know that arteries have higher blood pressure than veins, which have lower blood pressure. And so, it's actually the case that blockages in arteries would be more life-threatening because they have a higher blood pressure, but that's not what it says. So, we can eliminate answer option d. So, again, b here is the correct answer to this problem. That concludes this problem, and I'll see you all in our next video.

Which of the following is a reason that the retina, kidney, & spleen may be more susceptible to cell death than other organs?

• A. Arteries that supply these organs do not have many anastomoses.
• B. Veins that carry blood away from these organs do not have many anastomoses.
• C. There are very few arteriovenous anastomoses near these organs.
• D. They have many capillary beds.

Here’s what students ask on this topic:

What are blood vessel anastomoses and why are they important?

Blood vessel anastomoses are connections between blood vessels that allow for alternative pathways for blood flow. They are crucial for maintaining blood supply to tissues, especially when primary vessels are compromised due to damage or blockage. There are three main types: arterial anastomoses (connecting arteries), venous anastomoses (connecting veins), and arteriovenous anastomoses (linking arteries directly to veins, bypassing capillaries). These structures form collateral channels, ensuring that tissues receive adequate blood supply, particularly in joints and vital organs. Understanding anastomoses is essential for grasping vascular health and circulation dynamics.

What are the different types of blood vessel anastomoses?

There are three main types of blood vessel anastomoses: arterial anastomoses, venous anastomoses, and arteriovenous anastomoses. Arterial anastomoses involve the merging of arteries and are commonly found in joints and near vital organs. Venous anastomoses involve the merging of veins and are significantly more common, providing extensive collateral circulation. Arteriovenous anastomoses connect arteries directly to veins, bypassing capillaries, and are found in areas like the skin, fingers, toes, and ears. Each type plays a crucial role in ensuring continuous blood flow, especially when primary pathways are obstructed.

How do collateral channels formed by anastomoses benefit the body?

Collateral channels formed by anastomoses provide alternative pathways for blood to reach its destination when primary vessels are compromised. This is vital for maintaining tissue viability during events like vessel damage or blockage. For example, in joints like the elbow, collateral channels ensure blood flow despite movements that might hinder primary vessels. In vital organs like the brain and heart, these channels prevent tissue death by providing continuous blood supply. Overall, collateral channels enhance the body's resilience to vascular obstructions, ensuring that tissues and organs receive the necessary blood flow.

Why are venous anastomoses more common than arterial anastomoses?

Venous anastomoses are more common than arterial anastomoses because veins have a greater capacity for forming collateral channels. This extensive network of venous anastomoses provides multiple alternative pathways for blood to return to the heart, making the blockage of a single vein less life-threatening compared to an arterial blockage. The high prevalence of venous anastomoses ensures that blood can be rerouted efficiently, maintaining adequate circulation and reducing the risk of tissue damage due to venous obstructions.

What are terminal blood vessels and why are they significant?

Terminal blood vessels, also known as end blood vessels, are non-anastomosing vessels that do not form connections with other vessels. This means they lack collateral channels, making them more susceptible to tissue death upon obstruction. Organs supplied by terminal blood vessels, such as the kidneys, spleen, and retina, are at higher risk of damage if these vessels become blocked. Understanding terminal blood vessels is crucial for recognizing the vulnerability of certain tissues and the importance of maintaining unobstructed blood flow to these areas.