In this video, we're going to talk about the integumentary system's first method of thermoregulation, which is vasoconstriction and vasodilation and so altering the diameter of blood vessels in the dermis of our skin, which we know is near the surface of the skin. Actually thermo regulates the body allowing our body to maintain internal body temperature despite the fact that the temperature on the outside of our bodies can change. And so the term vasoconstriction refers to blood vessels constricting, which means that those blood vessels decrease in their diameter. Now, the vasoconstriction of blood vessels occurs when the body is cold. And what helps me remember that vasoconstriction occurs when the body is cold. Is the co in constriction reminds me of the co in cold. And so when blood vessels and the dermis near the surface of the skin undergo vasoconstriction, this actually decreases blood flow to the skin. And ultimately, this allows the body to retain heat under cold conditions. Now, the reason that the body is able to retain heat through vasoconstriction is because with a decrease in blood flow to the skin, there is less blood near the surface of the skin and less blood radiating heat to the external environment. And so ultimately, we are able to retain heat by preventing heat loss to the environment through vasoconstriction. Now, on the other hand, vasodilation is a term that refers to blood vessels dilating or increasing in their diameter. And this occurs when the body is hot or when the temperatures are high. And so, notice that vaso dilation rhymes with high temperatures. And so hopefully, that can remind you that vasodilation occurs when the body is hot. Now, when blood vessels in the dermis near the surface of the skin undergo vasodilation, this actually increases blood flow to the skin. And with increased blood flow to the skin, blood will be rushing toward the surface of the skin. And that means that more heat can radiate from the blood to the external environment, allowing our body to cool off again by facilitating heat loss to the environment. And so let's take a look at this image down below where we can start to piece things together. And notice that on the left hand side, we're focusing on vasoconstriction. Whereas on the right hand side, we're focusing in on vasodilation. Now recall that vasoconstriction uh occurs when it's cold outside and when it's cold, the blood vessels are going to constrict. And so notice that here we have these little snowflakes to show you that uh it is cold and notice that this person is shivering. So we know it's really, really cold and notice that their blood vessels are actually constricting, their diameter is smaller. And so here, the diameter of the inside of the blood vessel is very, very small. And so ultimately, what this means is less blood rushing toward the surface of the skin. And that means that there will be less heat radiating from the blood to the external environment. And so notice that these little yellow arrows that you see throughout represent heat, the body's heat loss. And so there's a lot less heat loss when uh vasoconstriction of the blood vessels in the dermis occurs, allowing the body to retain heat and ultimately helping to warm the body. Now, on the right hand side, we're showing you vasodilation and again, vasodilation occurs when it's hot outside and the temperatures are high. And that allows the blood vessels to widen or to dilate if you will. And so notice that the diameter of the blood vessel here is much, much larger in comparison to the diameter of the blood vessel uh with vasoconstriction on the left hand side. And so when the blood vessels dilate like this, more blood rushes toward the surface of the skin, and that allows heat to radiate from the blood to the external environment. And so notice that there's a lot more heat loss with the vasodilation of the blood vessels near the surface of the skin. And so that will facilitate heat loss to help cool off the body under these hot conditions. And so when there's more blood rushing to the surface of your skin, that can actually allow for your skin to turn a reddish color. And so that's responsible for the red flushing face that you get when your body is really, really overheated. And so this year concludes our brief lesson on the vasoconstriction and vasodilation of blood vessels in the dermis of the skin to allow for thermoregulation. And we'll be able to get some practice learning this and talk more about thermoregulation via sweating as we move forward. So I'll see you all in our next video.