胰腺外分泌腺

so the next organ we're going to talk about in our toward abdomen is the pancreas and I've drawn the pancreas right here and let me just write that out this is our pancreas which I believe you may have heard about before the pancreas sits below and behind the stomach and it kind of hugs the first part of our small intestine here which I think you may now recognize is called the duodenum in fact it wraps around a little more than what I've drawn right here but just know that it sits back way back over here in fact some say that the pancreas sits in a completely separate compartment from our stomach our small intestine our large intestine even our liver it's it's not in the peritoneum the peritoneum is where the rest of our guts sit the peritoneum is just a fancy word for the abdomen so our stomachs it's in our peritoneum our liver sits in our peritoneum the small intestine the large intestine all these guys sit in our peritoneum but our pancreas is different because it sits in the retroperitoneum and when we say retroperitoneum that means it sits in the back of the abdomen now it's not there alone a lot of our big vessels that run through the abdomen are also there the abdominal aorta the inferior vena cava these things you may have heard of elsewhere but it sits in this very different compartment and in fact medical professionals the pancreas is actually a force to be reckoned with for a couple of reasons first of all it releases a bunch of powerful enzymes powerful enzymes that we're going to talk about in a minute and these powerful enzymes can digest a whole bunch of our macromolecules things that we eat but also the things that line our cell membranes or make up other parts of our body not just in the retroperitoneum but in the peritoneum the thorax everywhere else in our body so it releases powerful enzymes and to the pancreas is a little strange in that it's uninhabited uninflated which is different from other organs like the liver the livers got the liver capsule the kidney is covered by its own capsule but the pancreas is essentially a slurry of cells that's hanging somehow in the retroperitoneum and that makes it a little difficult especially for surgeons that have to operate nearby you don't want to mess with the pancreas because it's got all these powerful enzymes that could cause a lot of damage around it if they were released no wonder then the pancreas has sort of earned itself a special nickname many physicians consider the pancreas to be the Lion of the abdomen because of how important it is and additionally how powerful the enzymes are that come from it so just like the lion in the jungle you don't want to mess with the pancreas so let's take a few minutes then and talk about what makes the pancreas so special physiologically the pancreas releases two types of things or has two main components to it one there's the exocrine pancreas and the idea behind the exocrine pancreas is that it takes salts and write it down here enzymes so these powerful enzymes I talked about earlier it takes these salts and enzymes and releases them in the duodenum or the duodenum and I think you remember where that is that's the first part of the small intestine right after the stomach and so our exocrine pancreas has four main roles that it accomplishes so firstly as you may recall because the pancreas releases its contents into the duodenum think about what the duodenum is receiving right before hand well as we talked about in the video on the stomach we're getting a whole bunch of time that's been digested by gastric acid or hydrochloric acid and so we'll need something to neutralize all that acid and so the exocrine pancreas release bicarbonate the bicarbonate here will serve to neutralize our gastric acid so we will neutralize the pH or the very low pH that we're receiving from the stomach in the form of gastric acid and remember again the gastric acid is hydrochloric acid next as we move on we'll talk about some of those powerful James that we discussed earlier one of them that we've briefly mentioned when we were talking about the mouth is amylase and if you recall amylase is responsible for the breakdown of starch and if you remember starch is just a whole bunch of carbohydrates stacked upon one another and we break down starch into our smaller carbohydrates so I'll just write smaller carbs for right now and so that'll include things like those glucose monomers or even disaccharides and then another enzyme that we also release from the exocrine pancreas into the duodenum is something called lipase and lipase should be another throwback to the mouth because it's names suggest that it breaks down lipids so specifically it'll take triglycerides which I can draw here so here's a triglyceride right there and you've got these fatty acid chains that are coming off the glycerol head it'll take triglycerides and it'll break them down into free fatty acids and so those will look like this so that's the acid part and here's the fatty acid part as well as things like monoglycerides and monoglycerides look like this and we're calling them mono because they've only got one fatty acid chain on them we can also have diglycerides which I think you might be able to guess what these guys look like if I draw them out like here diglycerides are going to have two fatty acid chains on them there you go and then it also will release glycerol glycerol and glycerol is what happens when you get rid of all your fatty acid chains and so you'll have some of these guys and they're all owe a cheese right here so that's what your lipase will do and it's similar to the lingual lipase that you had in your mouth but in the mouth that was mainly for taste when you digested your triglyceride in the duodenum this enzyme works to break down triglycerides in a greater manner and then finally the last function of the exocrine pancreas involves its proteolytic enzymes so I'll just write proteolytic right here and I'll expand there are two types of proteolytic enzymes there's trypsinogen that it releases trypsinogen there's trypsinogen and there's also kymo this is a longer word kymo trypsinogen trypsin no Jin and I think there's a couple of light bulbs that should be coming on right now because whenever you see the suffix Oh Jen as we see down here that refers to something that's called a zymogen a zymogen which means an enzyme that isn't in active right now because it has an extra bond usually a peptide bond that needs to be broken in order for it to start doing its thing so trypsinogen is the inactive form of trypsin just like how chymotrypsinogen is the inactive form of chymotrypsin and these guys need to be activated and the way that's done is in the duodenum there's an enzyme that sits there called entero peptidase there's a whole bunch of entero peptidases that line the duodenum your entero peptidase will break down trypsinogen to form trypsin trypsin is the active form that's then going to be able to break down proteins and what we're doing here is actually causing a chain reaction because once trypsin is formed the next step in activating chymotrypsinogen is accomplished by trypsin trypsin will cleave your chymotrypsinogen to form and this is a very long word kymo trypsin chymotrypsin and these guys will go wreak havoc and break down proteins in the duodenum now my question to you is these are enzymes and they're inactive because of usually a single bond what happens when that bond that makes them inactive brakes say if you're in a car accident and you get hit in the stomach and there's enough force there that can provide activation energy to break a bond and turn trypsinogen into trypsin what would happen well as we mentioned earlier because the pancreas is uninhabited trypsin will go on to activate chymotrypsin a gene into the chymotrypsin and then will break down proteins wherever they see them and that can be membrane proteins they could be proteins that are in the surface of the duodenum they could be proteins that we digested in our food or they could be proteins that are present in the pancreas so you can see why the pancreas is so feared and that's why the pancreas is something you don't want to have damaged because we can activate these deadly enzymes that should be working in the duodenum