So here we have an example problem that asks, which of the following is not common to both lymphatic trunks and cardiovascular veins? And we've got these 4 potential answer options down below. Now option a says, a wall consisting of three tunics or layers. And, of course, recall from our last lesson video that this is something that actually is common to both lymphatic trunks and cardiovascular veins. Because recall that the larger vessels of both the lymphatic system and the cardiovascular system can have three tunics or three layers in their walls.
And so because we're looking for what is not common to both of these, we can eliminate answer option a. Now, option b says transport of erythrocytes, which recall erythrocytes are red blood cells. And these erythrocytes, or red blood cells, are really maintained within the traditional vasculature of the cardiovascular system, including cardiovascular veins. But these erythrocytes or red blood cells are not transported by the lymphatic system, including lymphatic trunks, which means that option b is something that is not common to both lymphatic trunks and cardiovascular veins, meaning that option b is the correct answer to this example problem. But let's check option c and d just to be sure.
Option c says, valves to prevent backflow. Now recall that cardiovascular veins, especially the veins of the limbs, such as the arms and legs, can have valves in them to prevent the backflow of blood. And recall that lymphatic trunks and valves of the lymphatic system can have even more valves than cardiovascular veins, and so both of them can have valves to prevent backflow. And so for that reason, we can eliminate answer option c, and then option d says anatomical variations among the population of the exact locations of vessels. And, of course, there is going to be variations across different individuals for both cardiovascular veins and lymphatic trunks.
And so, because this is something that is common to both of these, we can eliminate answer option d. And, of course, this means option b is the correct answer. That concludes this example, so I'll see you all in our next video.
