 There you go, Dr. O. In this video we're going to talk about deglutition or swallowing. So deglutition is the technical term for swallowing. Swallowing might seem simple. We do it all day. We drink stuff. We eat stuff. But it's a very complex process. It's going to involve the movement of the tongue. It's going to involve the movement of the pharynx and multiple structures and muscle contractions. It's going to involve the medulla, oblongata, et cetera, et cetera. So we're going to break swallowing down into three phases. The voluntary phase, which you'll also hear called the oral phase, the pharyngeal phase, and then the esophageal phase. So here we're at the voluntary phase. Reason it's called that is because you can decide when to swallow something. So with the last voluntary action involved in swallowing is the initiation of swallowing. We trigger, we voluntarily trigger the events that lead to swallowing, excuse me. But in the end, your autonomic nervous system will take over, specifically your parasympathetic division. So the voluntary phase, what happens here is the tongue, as you can see from that arrow. The pharyngeal is going to push up and back and actually pull that bolus of food towards your pharynx. While that's happening, your soft palate and uvula is flipping up to make sure the food doesn't go up and into your nasal cavity. You don't want that. And then the pharyngeal, the constrictor muscles are going to start to literally squeeze, using peristaltic contractions, squeeze that food from your mouth to the oral pharynx and then down towards the laryngeal pharynx. So that is going to be with the last voluntary action, this initiation of swallowing. So the next two phases are going to be involuntary. So here we do see the pharyngeal phase, hopefully you know what the pharynx is. So notice that the uvula and soft palate are still flipped up to make sure the food can't, food or drink can't go out your nose. If you ever had that happen, you know it can be very painful. But you also notice down here now that the epiglottis has flipped over, flipped down to cover the glottis, the opening to the trachea. So the key thing to remember with swallowing is your throat, your pharynx will actually climb up as you swallow. You can feel that every really sore throat. So as your pharynx pops up, you've already closed off the nasal cavity there with the soft palate and now this climbing action is going to have the lid of the larynx, your voice box, the epiglottis, is going to flip down now and cover the glottis. So potentially there were three different directions food or drink could go. About your nose, you've blocked that one. Down the wrong pipe, as they say, into your airways, you've blocked that one. So the last place that food or drink can go is down into the esophagus now. So I mentioned this before. All this is being controlled by the deglutitian centers in the Medulla oblongata. Probably there is one more interesting thing here. When you swallow, there is something called deglutitian apnea. So for a brief period of time, while you're swallowing, it will let you will stop breathing. So swallowing generally takes maybe a second for a liquid, four to eight seconds for solids, that kind of stuff. But there's a period in there where you are not breathing. That's called deglutitian apnea. So for now to get, so we've gone from the oral cavity to the pharynx and the pharynx into the, and now we're heading into the esophagus. Let's go ahead and look at the esophageal phase. This is going to involve both your upper and lower esophageal sphincter. So for food to move from the food or drink, sorry, to move from the pharynx into the esophagus, the upper esophageal sphincter is going to have to open because the esophagus is usually closed. Remember your trachea has to stay open all the time. Your esophagus is usually closed and only opens when it's needed. So you've got, so the upper esophageal sphincter will relax, allowing the food to enter the top of the esophagus. The esophagus is a mixture of skeletal muscle and smooth muscle. But as you travel down into the esophagus, it becomes less and less skeletal muscle and then for the last third or so of the esophagus, the skeletal muscle is gone completely. Which again means that we initiate swallowing, but the process becomes more and more unconscious or subconscious once it's triggered. So here you can see where the upper esophageal sphincter would be. Not really the most important thing clinically is not the upper esophageal sphincter. So as food has been squeezed through your esophagus using waves of peristaltic contractions, it now reaches the lower esophageal sphincter. So a reflex causes the lower esophageal sphincter to pop open and allow that bolus of food to pop down into the stomach. But so this lower esophageal sphincter should always be closed. It opens to allow food to pass and then should close back up. If it doesn't and this lower esophageal sphincter stays open, that can allow for the reflux of material from your stomach like stomach acid into your esophagus. Your stomach has a beautiful thick layer of mucus, or at least it should, to protect different stomach acid, but your esophagus does not. So if stomach acid is refluxing or splashing up into your esophagus, that will lead to pain like heartburn. And that's also why chronic persistent heartburn is called GERD. Because the other name for the lower esophageal sphincter is the gastro esophageal sphincter. So GERD is gastroesophageal reflux disease. Let's see. So as far as how much stomach acid you have determining heartburn, it really doesn't. Your stomach can be full of acid as long as that sphincter stays closed. This is why some researchers has shown that things like melatonin that play a role in the sphincter control of your lower esophageal sphincter, they can actually decrease heartburn. I mean, just there's all sorts of interesting things there. I think there's a link between an overgrowth of microbes like bacteria in your small intestine or potentially even in the stomach occasionally, leading to gas production. And this gas production that happens, like if your food is basically putrifying or something like that, the pressure from this gas can actually pop the lower esophageal sphincter open too. So heartburn is a very serious condition. Stomach cancer is still the second leading cause of cancer death in the world. Esophageal cancer is very dangerous too. So like stomach, health, esophageal health, very, very important. But if you have heartburn, don't always just jump to acid lowering medications because we need acid in our stomach as well. So see a specialist. You know, I'm not medical advice, just my opinion, but I think you should see someone figure out the actual cause of your problems so you can get better without always having resort to getting rid of the acid in your stomach because it's there for a reason. OK, so that is the deglutition or swallowing process. I hope this helps. Have a wonderful day. Be blessed.