 I'm going to do a relatively short video here where we talk about the three types of muscle tissue. So we're going to cover them in detail when we talk about the heart and the scalp of muscles and your hollow organs. We're just talking about muscle as a tissue here. So muscle has properties that allow it to produce movement. Number one, muscle cells are all excitable, which means they respond to a stimulus, the stimulus usually being from your nervous system, telling the muscles to do their job. They contract, they're contract down meaning they shorten and as they do so they pull and that's because muscle cells are going to be connected to things and where they're connected it's going to pull and shorten them. So pretty straightforward. The three types of muscle tissue that we have, we have skeletal muscle, cardiac muscle and smooth muscle are usually the order that we learn them in. Let's go ahead and look at skeletal muscle. I want you to know three key words for every one of them at this point. Like I said, we'll dive into much more detail later. So skeletal muscle, number one, is striated. Striated means it has a banded appearance, as you can see there on the top, and that's because of these sarcomeres, which we'll cover later. So just remember for now, striated means it has a banded appearance. It's how it's organized. It means it's very organized. So striated or banded appearance, number two, skeletal muscles are voluntary, meaning we can control them, right? We control our muscles. It doesn't mean we have to all the time. Reflexes will control them involuntarily, but we can voluntarily control our skeletal muscle. We don't do that with your heart muscle, for example. And then number three, skeletal muscle cells have multiple nuclei. That's kind of, I mean, it's true and not true, and that's because muscle cells are actually big muscle cells, muscle fibers are formed by mild blasts, muscle stem cells. So the reason that a muscle cell has multiple nuclei is it used to be tens or hundreds or thousands of muscle stem cells that fuse together. So skeletal muscle thinks striated or banded appearance, voluntary, meaning we can control it, and multiple nuclei. Next we have cardiac muscle. Cardiac muscle is also going to have that striated, banded, organized looking appearance. It's going to be involuntary, though, thankfully we don't have to say, contract, relax, contract, relax, use our heart. So heart muscle or cardiac muscle is involuntary, and each cardiac muscle cell is going to have a single nucleus. So heart muscle thinks striated, involuntary, single nucleus. The other key thing about cardiac muscle, though, is that these cells are connected by a specialized cell junction called intercalated discs. So the reason that's important is it allows all the heart muscle functions as one unit. So one stimulus can actually cause the entire heart to contract. We'll cover that when we cover the heart. The other cool thing about cardiomyocytes or heart muscle cells is they can contract on their own intrinsic rhythm. So your heart doesn't have to be told by any other part of the body to contract and do its job. Now other parts of your nervous system can influence the heart, speeding it up, slowing it down, et cetera, but the heart works on its own rhythm, or at least it can. So that's cardiac muscle. And lastly, we have smooth muscle. So smooth muscle is the only one that's non-striated. It's kind of the cells are clumped together. They're spindle-shaped cells that look kind of like an upper lip to me. But they're non-striated because they're not very organized. They're kind of laid out in a different pattern. So they're not near as organized as the other types of muscles, skeletal and cardiac muscle. Smooth muscle is involuntary. You don't control it. And each cell has a single nucleus. So think non-striated, involuntary, and a single nucleus. So these spindle-shaped smooth muscle cells, where would you find them? All of your hollow organs are going to be lined with smooth muscle. Your airways, the blood vessels like your arteries, urinary system, digestive system, anywhere you have a hollow structure running in or through the body, it's going to be lined by smooth muscle. All right, so these are the three types of muscle tissue. We'll cover them all in great detail as we need to. I hope this helps. Have a wonderful day. Be blessed.