welcome back welcome back welcome back to science today we're going to be talking about the digestive system so as an introduction uh we're going to go through about 10 slides here so digestion is going to require two things it's going to require mechanical digestion and chemical digestion both of these are involved in breaking down the food mechanical digestion is literally grinding the food together that we start with our teeth there are other processes that are also going to be massaging the chemicals into the food by the contractions of our stomach and other things like that chemical digestion it's going to utilize different enzymes to break down many of the different kinds of macromolecules within our system the digestive system the organ of the digestive system is going to require mechanical and chemical digestion ingestion propulsion absorption and defecation the digestive system consists of the Elementor canal and the accessory organs so we're going to start with the alimentary canal what is the elementary canal this is the food passageway this is going to consist of organs that extend from mouth to anus so we are tube within a tube so mouth pharynx esophagus esophagus stomach small intestine large intestine and eventually the anal canal it's a muscular tube roughly eight meters long the accessory organs are going to be used and utilized in this process they're going to have secretions that are going to empty into the alimentary canal allowing for the digestion of many of the different food sources that we have included but not limited to salivary glands gallbladder pancreas to name a few here are the accessory organs that are going to be involved here salivary glands in the mouth we can see all of these different things that are going to be involved in this process of the breakdown of our food food stuff symbolus until it's to the point of being completely absorbed so the wall of the alimentary canal is composed of four layers those four layers are going to be going from innermost to outermost is the mucosa so mucosa muscularis and the serosa in the mucosal layer you're going to have a mucous membrane and it's going to have lots of folds on it the folds that exist within the digestive system is to increase the amount of surface area because the nutrients will be absorbed through the surface the more surface you have would be similar to having a longer intestine so our small intestine if it was way longer it would be equivalent to what it is now with all the different curvatures of the things going in and out of those different things this is going to absorb dietary nutrients secrete mucus and enzymes now just on the other side of the muco layer is going to be the submucosa some mucosa is going to nourish cells it's going to transport absorbed food molecules and eventually we're going to have this food taking into the blood supply the muscularis is going to have circular muscles as it's going around and this is going to be involved in two different parts one is going to be the movement of things in a non-directional form and there's also a directional form of contraction a peristaltic type movements that moves things through the system the outermost layer is the the seroso layer and the seroso layer just like other organs has a visceral peritoneal layer that's going to cover all this in the abdominal cavity here are these different layers and you can see the cutaways you can even see the mucosal layer submucosa and in closer might zoomed up you can see some of these things there so the mucosa layer with all the different surface area and you can see zoomed up the goblet cells that are there you can see the capillary bed and the lymphatic lacteal that's there you can see the submucosa a nourishing layer you can see the muscular layer that's there muscularis and then you can see the serosal layer that's on the outside that has the visceral layer that's on on that so two types of movements that we see in the elementary Canal one is the mixing movement you have your stomach and small intestines that are going to turn move things back around it is not directional it's just going to essentially mix massage back and forth in the fluids with the enzymes to make sure that we're coating getting as much exposure as possible on those food parts the propelling movements this is where we are moving things in a directional area and that process is called peristalsis if you took a balloon a long balloon like what clowns tie and put a marble in the balloon and your goal was to move the marble to the other end you could do it by alternating in the contractions of your fingers these alternation of contractions as it moves stuff downward that would represent a peristaltic movement peristalsis is the arithmetic contractions and a wave-like motion that moves food down essentially a structure so here we have the movement and here's the peristalsis right here moving this bolus all the way down through that peristaltic actions now Innovations of the elementary Canal you're going to have branches of the sympathetic and parasympathetic that's going to be involved here we know that parasympathetic is going to be the rest and digest so we're not surprised to see this having a major part in secretion in the motility now sympathetic is going to have an action if at some point we need to prevent the the Dead the rest and digest and move on to something so if we want to stop the secretion and motility the sympathetic nervous system would take care of that so the submucosal plexus is going to control secretion and the myantaic plexus is going to control the gastrointestinal motility the enter Endocrine cells these can be found in the stomach so they secrete and regulate the gastrointestinal organs and processes so these are hormones that are entire and taught entitled in programming uh the process all right guys let's dig into more of it in just a moment we'll talk about the math