 Hi everyone, I'm Leah your lead course instructor here at Advanced E-Clinical Training if you don't already know me by now but you should because we've been going over anatomy and physiology and Today we are going to go over the gastrointestinal system so the gastrointestinal system here so functions of the gastrointestinal system there are four main ones so Motility is one so material motility refers to the movement of food through the GI tract through the process of ingestion mastication, which is chewing and dead lute Really part one. I'm Leah your lead course instructor here at Advanced E-Clinical Training and By now, you know that we have been going over anatomy and physiology And so today we are going to talk about the gastrointestinal system So there are four main functions of the gastrointestinal system and they include Motility so motility is referring to the movement of food through the GI tract through the process of ingestion chewing swallowing and then peristalsis Digestion the role of digestion I'm sorry the role of the digestive process is to break down these food compounds into Particles that are absorbable Micronutrients and to separate the individual nutrients from the complex food matrix that enters the body Through absorption that is the transport of Digested end products from the lumen of the GI tract to the blood or lymph Where it's absorbed and for absorption to happen the digestive food Must first enter the mucosal cells by active or passive transport processes and Then the fourth function of the gastrointestinal system is of course elimination So elimination of indigestible residues from the GI tract via the anus and the form of feces So the organs of the the digestive system can be separated into two main groups First we have the elementary canal also known as the gastrointestinal tract And its main function is to nourish the body and then we have the accessory Digestive organs and these organs are critical for Orchestrating the breakdown of food and the assimilation of its nutrients into the body So first we'll begin talking about the elementary canal organs The gastrointestinal tract and this first one is the mouth So food of course enters the digestive tract through the mouth We have the lips the lips protect the opening of the mouth We have our cheeks and the cheeks form the lateral or the sidewalls of the mouth We have the palate and the hard palate forms the top of the mouth or the anterior roof of the mouth And the soft palate forms its posterior roof or the bottom part of the mouth We have the usula and that is a fleshy finger-like projection of the soft palate Of course, we have the tongue and that's the tongue is a muscle that occupies the floor of the mouth and has several bony attachments and Two of these are to the hyoid bone and the styloid process of the skull Which we talked about in the musculoskeletal system and then we have the linguinal frenulum and this Is a fold of mucus membrane that secures the tongue to the floor of the mouth and limits Back movements or posterior movements. We also have the palentine tonsils and at the Top end of the oral cavity are a pair of masses of lymphatic tissue known as the palentine tonsils And then we have the linguinal tonsils and the linguinal tonsils cover the base of the tongue and just beyond Moving along with the elementary canal organs of the gastrointestinal system We have the pharynx and as you can see here from the mouth food passes posteriorly into the oral pharynx and the layer laryngeal pharynx so the oral pharynx is Behind or at the bottom to the oral cavity and the larynge Pharynx is continuous with the esophagus just below both of which are common passageways for food fluids and air Moving along we have the esophagus So the esophagus runs from the pharynx through the diaphragm to the stomach as you can see here in this Diagram It is approximately 25 centimeters or 10 inches long and the structure so the walls of The esophagus to the large intestines are made up of the same four basic tissues of Tunics that include the mucosa the sub mucosa The muscularis externa the serosa and the intrinsic nerve flexuses which you can see here in this diagram moving along to the stomach so The stomach's function is it acts as a temporary storage tank for Your food as well as a site for food breakdown. So the stomach has five distinctive Sections that include the cardiac as you can see here on this diagram The cardiac is right here and this is the top part of your stomach And it contains the cardiac sphincter which prevents food from traveling back up to your esophagus the fundus of The stomach is a rounded section next to the cardiac as you can see right here And it's below your diaphragm The next part of the stomach is the corpus or the body and this is the largest section of your stomach in the body Your body will begin to contract and begins to mix the food here so they Answering lies below the body of the stomach and it holds food until your stomach is ready to send it into your small intestines and then next we have the pylorus which is right here and this is the bottom part of your stomach and This includes the pyloric sphincter. So this ring of tissue controls when and how your stomach Contents move to your small intestines. Of course now we're going to talk about the small intestines So this is the body's Major digestive organ the small intestines So it extends all the way from the pyloric sphincter Remember, which is at the end of the stomach to the large intestine and it is the longest section of all of these Elementary tubes with an average length of 8 to 20 feet long subdivisions of the small intestines include the duodenum the jejunum and the ilium We also have the eliocecal valve and this is where the ilium meets the large intestines And it joins the both of them together the small and the large intestines at this valve So we have microvilli and these are tiny projections of the plasma membrane of the mucosa cells that give the cell surface like a very fuzzy appearance so They help to complete the digestion of proteins and carbohydrates in the small intestines The villi are finger-like projections of the mucosa that help to give it a velvety appearance and feel much like like the soft nap of a towel and then we have pyrus patches and we talked about pyrus patches in our Lymphatic lesson, but they are actually a collection of lymphatic tissue found in the sub mucosa and it helps to increase the number Toward the end of the small intestines Next of course, we're going to talk about the large intestines So we went from the mouth to the esophagus to the stomach to the small intestines and now we're at the large intestines So the large intestines is a much is much larger in diameter Than the small intestines, but it is actually shorter in length It is only about five feet long as compared to the small intestines. So again The large intestines is they're only Bigger in diameter not length And extends all the way from the eliasacal valve all the way to the anus So the major function of the large intestine is to dry out Indigestible food residue by absorbing water and to eliminate these residues from the body As species so it frames the small intestines on all three sides and has the following subdivisions the cecum the appendix the colon the rectum and the anal cavity so you can see here and this diagram This is the large intestines right here and right in the middle. That's the small intestines so the cecum is a sac like and it's the first part of the large intestines and then you move on to the appendix and the appendix hangs from the cecum and is Kind of warm like and then we have the ascending colon So the ascending colon travels up the right side of the abdominal cavity and makes a turn to travel across the abdominal cavity the transverse colon is the This is where the ascending colon makes the turn that I just described Continues to be the trans transverse as it moves across transverse across the abdominal cavity and Then next of course we have the descending colon. So then this the large intensive large intestines Turns again at the colic or the splenic flexure and continues down the left side of the descending colon Then we have this sigmoid colon. So the intestines then enters the pelvis Where it becomes the S-shaped sigmoid colon and then we have the anal canal And that ends at the anus which opens to the exterior of the body, of course, and then we have the external anal sphincter And this anal canal has an external voluntary sphincter The external anal sphincter is composed of skeletal muscle. So moving on to now to the accessory Digestive organs or parts first remembering the beginning of this lesson. There are two main parts to the gastrointestinal tract So now we're moving on to the second part the accessory Organs or parts so the role the first one we're going to talk about are the teeth So the role the teeth that play The role the teeth play in processing Food obviously, you know, it doesn't need a whole lot of introduction So we masticate or chew by opening and closing our jaws and from moving the food side to side While continuously using our tongue to move the food between our teeth So next we have the salivary glands as part of the accessory digestive Organs of the gastrointestinal system So there are three pairs of salivary glands that empty their secretions into the mouth We have the parodic glands and these large parodic glands are Interior to the ears and empty their secretions into the mouth as you can see right here Then we have this submandibular and this sublingual glands and These glands empty their secretions into the floor of the mouth through tiny ducts can think of these if you Eat or if you eat something Very sour like a lemon you can sometimes feel the sublingual glands just start to excrete Their secretions that's where they come from. So next we have saliva So the product of the saliva glands Is saliva obviously and it's a mixture of mucous and cirrus fluid and then we have salivary Amylase and this is a clear cirrus portion that contains an enzyme Which is very important. It's in a bicarbonate rich juice that begins the process of starch digestion in the mouth Moving on to the pancreas So only the pancreas produces enzymes that break down all caloric glories of digestible foods So the pancreas is a gland that extends across the abdomen from the spleen to the duodenum But most of the pancreas lies posteriorly To the parietal peritoneum So pancreatic pancreatic enzymes Are secreted in the duodenum and an alkaline fluid that neutralizes the acidic chime coming in from the stomach because of the stomach is very Is known to be a very acidic a very acidic environment. So now this is where all that acid is neutralized And then of course the endocrine function of the pancreas, which we talked about in our endocrine lechthin Also Obviously has endocrine functions. It produces hormones such as insulin and glucogen Moving on to the liver So the liver is the largest gland in the body. It's located under the diaphragm more to the right side of the body The liver has four lobes And it is suspended from the diaphragm and abdominal wall by delicate by a delicate mesentery cord The liver's digestive function is to produce bile So bile is a yellow to green watery solution containing bile salts, bile pigments, cholesterol phospholipids and a Variety of electrolytes bile salts Do not contain enzymes, but it's bile salts emulsify fats by physically breaking down large fat globules into smaller ones And this helps to provide more surface area for the fat digesting enzymes to work on Moving on to the gallbladder So while in the gallbladder bile is concentrated by the removal of water The gallbladder is a small thin walled green sac that hides in a shallow groove in the inferior surface of the liver As you can see right here in this diagram And when food is not occurring I'm sorry when food digest this digestion is not occurring bile backs up The cystic ducts and enters the gallbladder to be stored here So let's break this all down What we just talked about so stages of digestion Step one, of course, we're chewing we're wetting the food with saliva in the mouth We're swallowing the food the saliva in the mouth starts to break down the carbohydrates Next we're swallowing so after we swallow food enters our esophagus, and this is where the parastolic Propulsion of food through the esophagus to the stomach so the movement Of food through the esophagus here to the stomach Stage three is stomach digestion and this is where proteins are digested By the way of gastric acid and other digestive juices moving along to the small intestine And of course the liver and the pancreas produce digestive juices and enzymes to digest food Digestion of carbohydrates fats polypeptides nucleic acids All happen here Then we move down to the large intestines is where absorption begins And then to stage six or step six waste elimination so The physiology of digestion so it's food ingestion and breakdown So of course we've talked about this in the beginning once food is placed in the mouth Both mechanical and chemical digestion begins So of course, there's the physical breakdown We're chewing the food. It's broken down into smaller particles And then the chemical breakdown begins and so When the food is mixed with saliva, that's where the saliva amylase begins the chemical digestion of starch. So remember that starch Is begun to being broke down in the mouth So stimulation of saliva. So when food enters the mouth stimulation of saliva from the Salivary glands begins and then the passageways of course the pharynx and the esophagus Have no role digestive function. They just simply provide pass a passageway to carry food from the mouth To the next processing site, which is the stomach so next The next stage of the physiology of digestion is food propulsion swallowing and peristallis so Degligution or swallowing is a complex process that involves the coordinated activity of several Structures including the tongue the soft palate the pharynx and the esophagus We have the bucle phase of swallowing and the first phase the voluntary bucle phase occurs in the mouth Once the food has been chewed and while mixed with saliva the bolus is forced into the pharynx by the tongue Then moving on to the pharyngeal esophageal phase, which is the second phase of the involuntary And it's an involuntary phase So this transports food through the pharynx and the esophagus So the parasympathetic division of the autonomic nervous system controls this phase and promotes the mobility of the digestive organs from this point on Food routes so all routes that the food may take except the desired route Distal into the digestive tract are blocked off. So the tongue blocks off the mouth Not allowing food to come back from the pharynx or the esophagus into the mouth So the soft palate closes off the nasal passages They're there the larynx rises so that it's opening is covered with the epiglottis So that prevents the epiglottis actually prevents food from going down into Your lungs And then it enters the stomach and so once the food reaches The very end of the esophagus is it oppresses against the Cardiosophageal sphincter causing it to open and that's when the food then enters the stomach Next we're going to talk about food breakdown during the physiology of digestion So the site smell and taste of food stimulate Parasympathetic nervous system reflexes which increase the secretion of gastric juice by the stomach land. So Gastric juice is just a secretion of Gastric juices and it's regulated by both the neural and humoral factors Gastron So the hormone the hormone gastron stimulates the stomach glands to produce more pepsigen mucus and hydrochloric acid Pepsigen So the extremely acidic environment that hydrochloric acid provides is necessary because it activates this Pepsigen to pepsin The active protein digestive enzyme renin so renin The second protein digestive enzyme produced by the stomach works mostly on milk protein and converts it into a substance that it looks like sour milk And then there's food entry. So as food enters and fills the stomach The stomach walls begin to stretch at the same time as gastric juices are being secreted And then the stomach um wall activation. So muscles of the stomach walls Become active so they churn food breaking it apart physically while simultaneously mixing the food with the gastric juices So that chime is formed moving on to Food propulsion. So peristalsis as we talked about previously is the movement of food towards the digestive tract peristalsis so Once food is mixed That's when peristalsis begins in the upper half of the stomach and the contractions increase in the stomach Enforce as the food approaches the pyloric valve Once it gets to once the food or the contents get to the pyloric passage of the stomach This is where The pyl, so the pylorus of the stomach only holds about 30 ml of chime So it allows only liquids and very small small particles to pass through the pyloric sphincter With each contraction of the stomach muscles sending around three ml's a less or less of chime into the small intestine Next we have that entero gastric reflex So when the duodenum is filled with chime a nervous reflex that entero gastric reflex Occur so this reflex actually slows gastric activity and slows the emptying of the stomach By inhibiting the vagus nerves and tightening the pyloric sphincter to allow time for intestinal processing to catch up Because you can't just empty all of the contents of the stomach Into the small intestine all at one time. So that's what this reflex helps with So moving on to absorption um of the physiology of digestion so Food reaching the small intestine is only partially digested carbohydrates and protein digestion though has begun But digestion of fats has not We have brush border enzymes and these are the microvilla the small intestine cells that contain The brush border enzymes that break down double sugars into simple sugars and complete the protein digestion And then foods entering the small intestine are saturated with enzyme rich pancreatic juices from the pancreas along with brush border enzymes That complete the digestion of starches and are totally responsible for fat digestion and digestion of Newly nucleic acids So next when chime enters the small intestine it stimulates the mucosa cells to produce Hormones called secretin and this helps to release the pancreatic juices and bile And then absorption of water Of the end of products of digestion occurs in the small intestines Most substances at this point are absorbed through The intestinal cell plasma membranes by the process of active transport Then we have diffusion so lipids or fats are absorbed passively by the process of diffusion And then debris at the end of the ilium which remains is some water some indigestible food materials large amounts of bacteria All of this remaining debris enters the large intestines through the iliocecal valve We've did talk about food propulsion. So parastylysis is the major major means of propelling food through the digestive tract um The way that food is moved through the small intestines Is like the way that toothpaste if you can think of toothpaste being squeezed from the tube This is done with um rhythmic contractions so rhythmic contractions of the segmental movements produced can constructions of the intestines that mix and chime With the digestive juices and help to propel the food through the intestines Moving on to food breakdown and absorption So the contents that are now in the large intestines Contain little nutrients and will remain there for 12 to 24 hours um the bacteria that live in its lumen of the large intestines metabolize some of the remaining nutrients releasing gases that continue to the odor of feces and flatulence flatulence or gas about 50 mls of gas is produced by humans each day much more when certain carbohydrate rich foods are consumed um So the large intestines is limited to the absorption of vitamin k some b vitamins some ions and most of the remaining water And then bc so this product is delivered to the rectum contains the undigestible food residues mucous Lots of bacteria and just enough water to allow passage So that was a lot and there's a lot to know in the gastrointestinal system um If you have questions about it if you have concerns if you need any clarification You know that you can always email me or you can schedule office hours with me But I appreciate you all sticking with me through this We're almost done here. I hope you all have a wonderful rest of your day. Bye