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Digestive (GI) System (Gastrointestinal System) Gastro = stomach 1 Functions – – INGESTION Taking food in by mouth DIGESTION to break food down into simple molecules Mechanical: churning of food in the stomach, manipulation of food with tongue, tearing and grinding with teeth. Chemical: breakdown of food with hydrochloric acid – – ABSORPTION nutrients enter capillaries DEFECATION to eliminate solid waste products 2 Digestive Organs 3 Regional Terms Upper GI – Stomach and areas superior Lower GI – Areas inferior to the stomach 4 Abdominal Quadrants 5 Peritoneum and Mesenteries 6 Peritoneum and Mesenteries 7 OMENTA The liver is suspended by a mesentery called the OMENTUM. There are two omenta: greater and lesser. GREATER OMENTUM is flat, and is in front of the intestines like an apron. Its function is to store fat. LESSER OMENTUM is smaller. It is just some fat above the stomach. 8 Mesenteries 9 10 PERITONEAL CAVITY Why is this important? The peritoneum divides the abdominal cavity into three distinct regions: PERITONEAL CAVITY: digestive organs are here INFRAPERITONEAL CAVITY (inferior to peritoneum); where the bladder is RETROPERITONEAL CAVITY (posterior to it); where the kidneys are 11 PERITONEAL CAVITY This is clinically important because if you tear something in the GI tract (ruptured appendix), bacteria go out into the peritoneal cavity, affects all the organs there, which is the entire GI tract. Bleeding in the kidney will accumulate in the retroperitoneal cavity. Infection in the urinary bladder doesn’t affect the peritoneal cavity. Bleeding and infection are confined to one compartment. 12 Mouth Oral Cavity – Hard and Soft Palate Tongue – Lingual Frenulum Salivary Glands – Parotid, Submandibular, Sublingual Teeth 13 ORAL CAVITY Lined by non-keratinized stratified squamous epithelium. The transition between the skin (keratinized) and the non-keratinized area is the LIPS. You can see what happens when the lips dry out; becomes cracked because the lips don’t have as much keratin as the skin. – PALATE (ROOF of mouth) HARD PALATE: bone SOFT PALATE: soft tissue (can feel with tongue on roof) 14 Mouth 15 Figure 22.8a TONGUE Your tongue is the only muscle in your body that is attached at only one end. The tongue is all muscle, but it is different than all other muscles of the body, where the fascicles are arranged in a particular order. The fibers of the tongue go in all directions, and have no fascicles good ROM. Some people can curl tongue, others can’t. The LINGUAL FRENULUM is the flap of skin under the tongue at the midline. If it is too short, it limits mobility, called tongue-tied. Treatment is to cut it. 16 Figure 22.8b 17 Salivary Glands 18 SALIVARY GLANDS Produce saliva – Names of some salivary glands: Parotid (largest). Mumps is a virus that attacks here. Submandibular Sublingual – Functions of saliva To moisten food so you can swallow, especially dry food like crackers. Saliva is made of mucus and water. The mucus in the saliva is what moistens the food. To inhibit growth of bacteria (which like dark, warm, moist areas). What does this are the antibodies, enzymes, and macrophages in the saliva. 19 Saliva Saliva is not used for digestion of food. There is an enzyme in saliva that breaks down starch, but it takes hours. It is used to break down food stuck between the teeth so the bacteria can’t eat it and cause cavities. Saliva contains bactericidal enzymes that initiate the digestion of carbohydrates, and bicarbonate buffer. However, it does not contain enzymes that begin the digestion of proteins; chemical digestion begins in the stomach. 20 TEETH How many teeth does the average adult have? 32 How many DECIDUOUS TEETH (baby teeth that fall out)? 20 How many INCISORS (most anterior)? 8: for cutting like scissors How many CANINES? 4: for tearing How many PRE-MOLARS(BICUSPIDS = 2 roots)? 8:For chewing, some tearing How many MOLARS (TRICUSPIDS = 3 roots)? They are the most posterior; 12: For chewing, some tearing. The 4 most posterior ones are called WISDOM TEETH, which erupt at age 20, but sometimes grow crooked, called “impacted” 21 STRUCTURE OF TOOTH GINGIVA are the gums CROWN is the area above the gingiva ROOT is embedded in a socket in the bone. In the maxilla, the root can extend into the maxillary sinus. Damage to the sinus can be a lot of problems. ENAMEL is the external layer of the tooth. It is stronger than bone, but does wear out. It is suppose to be ivory color, not white. Whitening procedures scrape away outer oxidized layer, to expose the layer underneath, which is white, but it will oxidize, too. DENTIN is deep to the enamel. It is like bone, with living tissues and cells. PULP CAVITY with PULP is deep to the dentin. It has blood vessels and nerves. PERIODONTAL LIGAMENT attaches the tooth to the bone. It’s like periosteum. Disease of this structure is 22 the most common cause of tooth loss in adults. Tooth Structure Figure 22.11 23 Tooth Problems When bacteria eat away at the enamel, what’s it called? CARY (CAVITY) The dentist removes a larger area than where the bacteria destroyed, and fills it in. If the cavity extends into the pulp cavity, there is no way to clean it up. The treatment is to make a big hole, scrape out the pulp, and fill up the whole thing = ROOT CANAL. This is a dead tooth, but still there. Bacteria between the gingiva and tooth causes inflammation of the gingiva = GINGIVITIS. When it gets worse, the gingiva pulls away from the tooth and the bacteria extends down to the periodontal ligament = PERIODONTITIS. This is the major cause of tooth loss. The tooth loosens and falls out. That’s why you need to floss. 24 Cavity (called a “cary”) 25 Plaque on Tooth 26 X-ray of Teeth 27 X-ray of Teeth 28 Fun Facts The enamel in your teeth is the hardest substance in your body. Your teeth start growing 6 months before you are born. If you are right handed, you will tend to chew your food on the right side of your mouth. If you are left handed, you will tend to chew your food on the left side of your mouth. 29 Fun Facts Termites chew up dirt and dung and make massive homes. If they were the size of a human, they could make a home taller than the Empire State Building. They also put in air conditioning systems, covered walkways, stairs and gardens. Every person has a unique tongue print. A giraffe’s tongue is 22 inches long What animal bite causes the most human deaths? Snakes take their toll, but Mosquitoes cause millions of deaths a year. The Komodo dragon has saliva so toxic with bacteria, it just bites it's prey and waits for it to die of infection a few days later. The average human produces enough spit to fill two swimming pools in their lifetime. 30 VIDEOS How Dentures are made VIDEO 31 GI Tract This is a tube through the body, forming the esophagus, stomach, small and large intestine. The GI tract functions to digest and absorb. – Esophagus – Stomach – Small Intestine – Large Intestine 32 NOTE When you are referring to a structure that has a cavity (stomach, esophagus, uterus, eye, etc), the layer that touches the lumen is considered the superficial layer, even though from the outside of the body it would be considered deeper. 33 Layers of GI Tube There are four layers: 1. MUCOSA (inner layer). The lining varies from region to region. – Epithelium – Lamina Propria: Loose connective tissue – Muscularis mucosae: very thin smooth muscle, causes little twitches within the mucosa. 2. SUBMUCOSA (moderate dense connective tissue). Lots of elastic fibers, blood vessels, and lymphatic vessels. 3. MUSCULARIS EXTERNA (smooth muscle layer with two parts: – Circular Layer (inner) – Longitudinal layer (outer) 4. Serosa 34 Serosa Mucosa Muscularis Externa Submucosa 35 3. Muscularis Externa Muscularis Externa is extremely important for digestion. It allows for 2 types of actions: a. PERISTALSIS: a rhythmic contraction to push something along. This pushes food down by smooth muscle contraction. b. SEGMENTATION: A back-and-forth squeezing of the muscle to grind up food. Food moves forward then backward a little, then forward again. Function is to churn up the food inside. Some areas have thicker smooth muscle = SPHINCTER. Circular muscles open and closes an opening. – Controls the flow of food from one region to another. 36 Layers of GI Tube 4. SEROSA is not in all regions (none in esophagus). – Simple squamous epithelium – Loose connective tissue – From internal to external, the layers of this tube are the mucosa, submucosa, muscularis, serosa. 37 Esophagus Extends from the oropharynx (back of the throat) to the stomach, about 25 cm long. The things that are specialized in the esophagus are: 1. MUCOSAL EPITHELIUM (non-keratinized stratified squamous epithelium). Why do we want stratified squamous here? Because that is the thickest type of epithelium. It protects against things you swallow; pointy potato chips, etc. Cuboidal would slough. 2. MUSCULARIS EXTERNUM in upper half = skeletal muscle, is under voluntary control. Lower half = smooth muscle, not voluntary. Food gets caught in the lower half because it hasn’t started peristalsis. 38 Cardiac Sphincter The esophagus goes through the thoracic cavity. It needs to go through the diaphragm’s opening (esophageal hiatus). It empties to the stomach through a CARDIAC SPHINCTER = a thickening of the muscularis externa. This is NOT A TRUE SPHINCTER. 39 Stomach Anatomy 40 Stomach: Functions Store Food Mechanically churns food into a paste called CHYME Kill bacteria Some digestion: of proteins Some absorption: of water, alcohol Gastric emptying is the release of food from the stomach into the duodenum; the process is tightly controlled with liquids being emptied much more quickly than solids. 41 STOMACH FUNCTIONS 1. Store Food, so it can be slowly released into a small intestine. Your whole Thanksgiving dinner can take your stomach diameter from 2” to 8” diameter. 2. Mechanically Churns food. Secretions from the stomach are added, turns everything into a gooey paste. When you throw up, you can see the enzyme secretions = CHYME. 3. Kill bacteria. The stomach is very acidic (pH 1) like battery acid. Chyme will even eat through clothing. 4. Some digestion: of proteins. 5. Some absorption: of water, alcohol (alcohol is absorbed in the mouth, too!) Food takes four hours to completely leave the stomach. 42 FUN FACTS Body measurements for food portions 1 oz = a handful 3 oz = palm size (meat) cup = fist teaspoon = tip of thumb 43 REGIONS OF THE STOMACH 1. 2. 3. 4. 5. Cardiac region (near heart) Fundus (above the cardiac sphincter) Body Pyloric region PYLORIC SPHINCTER (a true sphincter) The lining of the stomach is folded over into RUGAE, to allow for expansion of the stomach. When the stomach is full, the rugae flatten out. 44 The Stomach Figure 22.14a 45 The Stomach Figure 22.14b 46 47 HISTOLOGY OF THE STOMACH Epithelium: simple columnar epithelium. – Its function is for secretion and absorption. Lamina Propria: contains gastric pits. 48 The Stomach Figure 22.15a-c 49 Stomach Cells CHIEF CELLS secrete an enzyme called pepsinogen. When pepsinogen is exposed to hydrochloric acid (HCl), it is cleaved into pepsin, its active form. Pepsin digests proteins. PARIETAL CELLS in the stomach secrete hydrochloric acid. They also secrete intrinsic factor, which is needed to absorb vitamin B12, which is needed to make red blood cells. 50 Intrinsic Factor A person who lacks intrinsic factor (such as those who have a stomach stapling procedure or gastric bypass) will not be able to absorb vitamin B12 and they will get a type of anemia called pernicious anemia. Treatment is injectable B12 shots monthly for the rest of their lives. They also have a new dissolvable oral form of vitamin B12 that enters the bloodstream directly from the mouth. 51 Gastric gland Figure 22.15a-c 52 PARTICULARS OF STOMACH Has a third layer of the muscularis externum: an OBLIQUE LAYER to churn food. 53 The Stomach Figure 22.14b 54 Problems with the stomach There are lots of goblet cells in the stomach which make mucus to prevent the stomach from digesting itself. Bacterial infection can erode this area = GASTRIC (or Peptic) ULCER. Acid Reflux – The acid in your stomach is strong enough to dissolve razor blades. The acid can creep up the esophagus and erode the lining there, causing heartburn. – The acid can stay in the stomach and cause an ulcer. In severe cases, the ulcers are so deep, they bleed, and the person might even vomit blood. – Tends to occur more when a person is under a lot of stress because more acid is produced. 55 Two major causes of Peptic (stomach and duodenum) Ulcers: 1) 60% of gastric and up to 90% of duodenal ulcers are due to a bacterium called Helicobacter pylori. – The body responds by increasing gastrin secretion, which is a hormone that causes HCl to be secreted, which erodes the stomach lining. 2) NSAIDs (non-steroidal anti-inflammatory drugs, such as aspirin) block prostaglandin synthesis. – Prostaglandins promote the inflammatory reaction. They also are found in the stomach, protecting it from erosion. 56 57 Stomach (gastric) ulcer 58 Risk and Transmission The lifetime risk for developing a peptic ulcer is approximately 10%. In Western countries the prevalence of Helicobacter pylori infections roughly matches age (i.e., 20% at age 20, 30% at age 30, 80% at age 80 etc.). Prevalence is higher in third world countries. Transmission is by food, contaminated groundwater, and through human saliva (such as from kissing or sharing toothbrushes or food utensils) 59 Problems With the Stomach The cardiac sphincter doesn’t close well, since it is not a true sphincter; consequences: – You can throw up (reverse peristalsis). Rats do have a true cardiac sphincter, and can’t vomit! – That’s why rat poison won’t kill people or dogs; they can throw it up. Another consequence: hiatal hernia. 60 HIATAL HERNIA Part of the stomach, protrudes through esophageal hiatus, causing pain and difficulty swallowing. It is the most common of all hernias. There is a great amount of acid reflux; erodes walls of esophagus, causing ulcerations of esophagus. Treatment is surgical; pull down the stomach, and tighten the hernia in a laparoscopic procedure. 61 62 Fun Fact Astronauts can't belch - there is no gravity to separate liquid from gas in their stomachs. 63 64 SMALL INTESTINE (Small bowels) These are the longest part of the GI tract (9-15 feet long, 1” diameter) In a cadaver, they are even longer, because the muscles relax. The small intestine is the most important region of the GI tract because almost all of the digestion and absorption takes place here. 65 Small Intestine Structure The small intestine needs a lot of surface area: 200 square meters, which is the floor space of a typical house. How do you get such a lot of surface area? There are lots of folds called PLICAE CIRCULARIS. Each of these folds also has folds, called VILLI. If you take velvet and fold it, the fold is the plicae, and the velvet hairs are villi. Each of the villi has epithelial cells called MICROVILLI, which make a BRUSH BORDER. 66 The Small Intestine Crypt of Lieberkuhn Figure 22.17a-c 67 Small Intestine Regions Duodenum “12 finger widths long” Jejunum “hungry when empty” Ileum “twisted” 68 DUODENUM This is the shortest region, only one foot long. It receives chyme from the stomach. This is where digestion begins. There are two ducts at the beginning of the duodenum from the pancreas and gallbladder. It is the site of action of liver and pancreas secretions. 69 The Duodenum Figure 22.16 70 Pancreas PANCREAS is an endocrine gland, and also participates in digestion (exocrine). Most of the digestive enzymes are made here. They go out the PANCREATIC DUCT to enter the small intestine. It also produces BICARBONATE (from a hormone called SECRETIN) to increase the pH (decrease the acidity) of the chyme coming from the stomach. If there is too much acid there, get a DUODENAL ULCER. 71 PANCREAS ACINAR CELLS: secretes digestive enzymes ISLETS OF LANGERHANS: secretes insulin 72 Pancreas Histology Figure 22.25a 73 Pancreas Acinar cells (secrete enzymes) Islet of Langerhans (secretes insulin) 74 Gall Bladder GALL BLADDER stores and concentrates bile, which emulsifies fat: It breaks down the fat into microscopic droplets which can be broken down by pancreatic enzymes. Fat doesn’t dissolve in water, so when you go to McDonalds and order the Big Mac, fries, and shake, you get 200 grams of fat (one week supply), which globs together in the intestine, and that much more bile is needed to break it down. 75 What Ronald McDonald is doing to your arteries 76 GALL BLADDER This is located inferior to the liver, and its function is to store and concentrate bile. Bile is a detergent/soap (not an enzyme) which emulsifies fat: It breaks down the fat into microscopic droplets which can be broken down by pancreatic enzymes. It does NOT make or secrete bile; that is done by the liver. Bile is made in the liver from Hemoglobin (Hgb), and also contains cholesterol and other things. The function of bile is to break down lipids (fats) so they can be digested. 77 Gallbladder and Pancreas Figure 22.16 78 Gall Bladder As the liver produces bile, if there is no food in the duodenum, the sphincter closes and bile backs up into the gall bladder. When there is food, the sphincter releases the bile. The gall bladder is similar to the stomach. It is lined with RUGAE (allows organ expansion). Has muscles around it to push bile out. 79 Gall Stones One function of the gall bladder is to concentrate the BILE, but if the bile salts crystallize, GALL STONES can form. The stones block the cystic duct, and causes a lot of pain as the bile backs up. Treatment is to cut the cystic duct and remove the gall bladder. Now that person can only eat small amounts of fats at a time. 80 Types of Gall Stones Stones made out of cholesterol (most common type). It has nothing to do with the cholesterol levels in the blood. Stones made from too much bilirubin in the bile. Gallstones are more common in women, Native Americans and other ethnic groups, and people over age 40. Gallstones may also run in families. 81 82 Jejunum JEJUNUM (“empty”) This is the part of the small intestine where most absorption occurs. It is 3 feet long. 83 Ileum ILEUM (“twisted”) is 5-10 feet long. It is the terminal portion of the small intestine. The rest of the absorption takes place here. 84 Histology of Small Intestine The intestines are lined with simple columnar epithelium with lots of goblet cells that make mucus for protection. However, the pancreatic enzymes can digest the mucus and the epithelial cells, so the lining of the small intestine is replaced every day. The basic functions of this epithelium are secretion and absorption. Absorption is a digestive process in which nutrients enter the capillaries. 85 Crypt of Lieberkuhn The INTESTINAL CRYPT (CRYPT OF LIEBERKUHN) is where the new epithelial cells come from, and they are pushed upwards into the villi to replace the digested cells. Also in this crypt are cells that produce enzymes and hormones. 86 Crypt of Lieberkuhn Lacteal 87 Crypt of Lieberkuhn Figure 22.17a-c 88 Absorption in Small Intestine In the villis is a fenestrated capillary bed (has holes in the walls of the blood vessels), which needs to absorb a lot of material. The small intestine absorbs carbohydrates, fats, and proteins (although protein enzymes have already begun working earlier in the digestive tract in the stomach). 89 Intestinal Villi 90 Lymphatics of Small Intestine There are also large lymphatic capillaries in each villis called LACTEALS, whose function is to absorb breakdown products of fat. The vessel is large so it won’t get clogged up. Under all this are the MUSCULARIS MUCOSA muscles which can twitch to move the villa so food does not get stuck. 91 Inguinal Hernia The inguinal canal is open in the male to allow for passage of the spermatic cord. In the female, the area is closed, but weak. When there is abdominal pressure (lifting a weight), a piece of small intestine can push out of this canal, causing pain. Symptoms and warning signs: http://www.symptomfind.com/diseases-conditions/hernia-symptoms-warning-signs/ 92 Problem with Small Intestine Crohn’s Disease – Autoimmune disease of the GI tract – Most common area affected is small intestine – Inflammation causes pain and diarrhea (may be bloody) – Genetic cause (high risk if siblings have it) – Usually occurs in males in their 20’s – No cure; just treatment of symptoms 93 Celiac disease (Sprue; gluten intolerance) Genetic autoimmune disorder of the small intestine, causing chronic diarrhea. The person is allergic to gluten. Causes destruction of microvilli and villi. It is characterized by having pale, loose and greasy stools (steatorrhoea) which are voluminous and malodorous. It often presents with abdominal pain and cramping, abdominal distension, and sometimes mouth ulcers. Without adjusting the diet, coeliac disease leads to an increased risk of adenocarcinoma (small intestine cancer). 94 Celiac disease (Sprue; gluten intolerance) They may develop ulcerative jejunitis and stricturing (narrowing as a result of scarring with obstruction of the bowel). The changes in the bowel make it less able to absorb carbohydrates, fats, minerals (calcium and iron), and the fat-soluble vitamins A, D, E, and K. Anemia may develop in several ways: iron malabsorption may cause iron deficiency anemia, and folic acid and vitamin B12 malabsorption may give rise to megaloblastic anemia. Calcium and vitamin D malabsorption may cause osteopenia (decreased mineral content of the bone) or osteoporosis (bone weakening and risk of fragility fractures). A small proportion have abnormal coagulation due to vitamin K deficiency and are slightly at risk for abnormal bleeding. Coeliac disease is also associated with bacterial overgrowth of the small intestine, which can worsen malabsorption or cause malabsorption despite adherence to treatment. 95 Celiac disease (Sprue; gluten intolerance) Celiac disease is caused by an allergy to gluten. Gluten is present in Wheat subspecies (such as spelt, semolina and durum) and related species such as barley, rye, triticale and Kamut. A small minority of coeliac patients also react to oats. It is most probable that oats produce symptoms due to cross contamination with other grains in the fields or in the distribution channels. Generally, oats are therefore not recommended. Other cereals such as maize (corn), millet, sorghum, teff, rice, and wild rice are safe for patients to consume, as well as non cereals such as amaranth, quinoa or buckwheat. Non-cereal carbohydraterich foods such as potatoes and bananas do not contain gluten and do not trigger symptoms. 96 Gluten-free diet Gluten is used in foods in some unexpected ways, for example as a stabilizing agent or thickener in products like ice-cream and ketchup. People wishing to follow a completely gluten free diet must also take into consideration the ingredients of any over-the-counter or prescription medications and vitamins. Also, cosmetics such as lipstick, lip balms, and lip gloss may contain gluten and need to be investigated before use. Glues used on envelopes may also contain gluten. Most products manufactured for Passover are gluten free. Exceptions are foods that list matzah as an ingredient, usually in the form of cake meal. A blood test for IgA antiendomysial antibodies can detect coeliac disease. 97 Large Intestine (Colon, or large bowel) This is about 5 feet long, diameter of 4”. Absorbs a LOT of water Absorbs salts and electrolytes (Na, K, etc) Stores feces for defecation (terminal portion) Contains abundant bacteria (E. coli): – – – – Make vitamins (B5, K, biotin) Allow material to move through large intestine easier Keep out harmful bacteria They eat things you can’t digest Fiber Some sugars that we don’t have enzymes for 98 Intestinal Gas When these bacteria are happy and dividing, they produce gas. If you are lactose intolerant, your are missing the enzyme for lactose so the bacteria gets more sugar and you get more gas! Beans also have these sugars, so they give you gas. Mexico has different strains of E. coli in their water; the two strains battle it out and you get diarrhea. Diarrhea is when the large intestine does not absorb water dehydration and electrolyte imbalance. Cholera is a disease which attacks the large intestine, preventing water absorption, and can be fatal in 24-48 hours. The difference between diarrhea and constipation is the amount of water absorbed from the large intestine. 99 ReynoldsUnwrapped.com offers FANTASTIC, inexpensive daily email subscriptions, where you can receive a HILARIOUS new cartoon every day, and it is a MARVELOUS idea for a UNIQUE gift for your family and friends as well. That is how I learned about this...one of my fellow teachers gave me a subscription as a birthday present. He also has FUNNY greeting cards and BEAUTIFUL paintings for sale as well. You can also get reprints suitable for framing, or originals. Here is more info about his work and a YOUTUBE video. https://nccnews.expressions.syr.edu/?p=11515 100 Regions of the Large Intestine Cecum Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Anus 101 Large Intestine Figure 22.18a 102 Gross Anatomy of the Large Intestine The large intestine is divided into regions, but they function the same. The ileum enters into the first region of the large intestine called the CECUM. The ileo-cecal valve separates these and controls the amount of chyme that enters into the large intestine. It also prevents the E. coli from leaving the large intestine and getting into the small intestine, where they would cause disease. 103 104 Appendix Below the cecum is the APPENDIX, which is a lymph node, but it contains E. coli as well. It might become inflamed, which closes off the opening: APPENDICITIS This is dangerous because It can rupture. Need antibiotics and surgery or can be fatal. Most common age for this is late teens to early 20’s because a child has a larger opening which shrinks with age. When you’re done growing, it’s done shrinking, so if you haven’t had a problem by then, you might be ok. 105 Large Intestine Up from the cecum is the ASCENDING COLON, TRANSVERSE COLON, and DESCENDING COLON. Then there is an “S” shaped section called the SIGMOID COLON, which leads to the RECTUM, and out the ANUS. 106 107 SIGMOID COLON This area allows for the passage of gas without passage of feces. The LEVATOR ANI MUSCLE, when relaxed, allows only gas to pas. When contracted, the feces can pass. Therefore, this muscle controls defecation by lifting the anal canal superiorly around the feces. Another thing that controls defecation is the INTERNAL and EXTERNAL ANAL SPHINCTER. The internal one is smooth muscle, and the external is skeletal muscle (voluntary control). The smooth muscles which line the large intestine work in coordinated fashion to move the feces out. It takes about 24 hours for food to be processed through the entire digestive tract. 108 Sigmoid Colon 109 Problems with Large Intestine DIVERTICULITITS INFLAMMATORY BOWEL DISEASE – Crohn’s Disease – Ulcerative colitis IRRITABLE BOWEL SYNDROME COLON CANCER HEMORRHOIDS 110 DIVERTICULITITS DIVERTICULUM (singular) DIVERTICUA (plural) can form, which are small pouches in the large intestine. They can become inflamed, usually from a small, hard piece of feces, causes the condition known as DIVERTICULITITS. These are painful and often need to be surgically removed. May be caused by lack of fiber, causing increased pressure in the colon. 111 Inflammatory Bowel Disease (IBD) IBD is a group of inflammatory conditions of the colon and small intestine. The major types of IBD are Crohn's disease and ulcerative colitis 112 Ulcerative Colitis The main symptom is constant diarrhea mixed with blood, of gradual onset. An intermittent disease, with periods of exacerbated symptoms, and periods that are relatively symptom-free No known cause, but may be genetic May be triggered by environmental factors Dietary modification may reduce the discomfort It is treated as though it were an autoimmune disease (anti-inflammatory drugs, immunosuppression) Colectomy (partial or total removal of the large bowel through surgery) is occasionally necessary, and is considered to be a cure for the disease. 113 Ulcerative Colitis 114 IRRITABLE BOWEL SYNDROME (IBS) IBS is a diagnosis of exclusion. Symptoms are chronic abdominal pain, bloating, and alteration of bowel habits in the absence of any detectable organic cause. May manifest as diarrhea or constipation or may alternate between the two. May be caused by infection, stress, or onset of maturity No cure; treatments attempt to relieve symptoms, including dietary adjustments, medication and psychological interventions. 115 COLON CANCER This is the #1 most deadly cancer (kills more people) because it metastasizes and there are no symptoms. It can be suspected by seeing blood in the stool; this is an easy test, but not very accurate. A more accurate test is a SIGMOIDOSCOPY. A tube is inserted into the sigmoid colon, done in the doctor’s office. The tube has a light, and they look for growths on the walls of the intestine = POLYPS, which are pre-cancerous growths. A COLONOSCOPY is done under general anesthesia since the tube has to go through the entire colon, but it’s more effective. 116 Colonoscopy Photos Ileo-cecal valve 117 HEMORRHOIDS HEMORRHOIDS are varicose veins in the rectum. There are large veins along the rectum, with nothing constricting them. They are common in pregnant women and in fighter pilots from the g-forces they pull. They can be surgically removed. 118 FUN FACTS ABOUT THE RECTUM A healthy individual releases 3.5 oz. of gas in a single flatulent emission, or about 17 oz. in a day. The bombardier beetle combines chemicals in his rear end and can squirt out boiling hot acidic liquid which quickly neutralizes any attack. All land spiders breathe through a hole on the rear part of their bodies. The Fitzroy river turtle absorbs two-thirds of the oxygen it needs through its rectum. 119 FUN FACTS HOW LONG DOES IT TAKE TO DIGEST A MEAL? Should be about one day. Because plant cells are made of cellulose and we cannot digest that, you can swallow a few kernels of corn (whole, without chewing), and you’ll be able to easily see them in your stools and find out how long it takes to go all the way through your digestive tract. 120 Hepatic Portal System Almost all of the blood coming from the digestive system drains into a special venous circulation called the portal circulation. This is because it contains all the nutrients and toxins that have been absorbed along the digestive tract from ingested food. Before these absorbed substances can go into the systemic circulation (the main blood circulation in the body), it must be filtered first to remove or detoxify toxic substances first. This filtering and detoxification is one of the 500+ functions of the liver. 121 Hepatic Portal System Many drugs that are absorbed through the GI tract are substantially metabolized by the liver before reaching general circulation. As a consequence, certain drugs can only be taken via certain routes. For example, nitroglycerin cannot be swallowed because the liver would inactivate the medication, but it can be taken under the tongue or transdermal (through the skin) and thus is absorbed in a way that bypasses the portal venous system. 122 A portal system is one that has two separate capillary beds between the arterial supply and the final venous drainage. 123 LIVER This is the largest internal organ of the body, located on the right side, below the diaphragm, and extends below the costal margin (can palpate). It has many functions and is the most complex organ except the brain. The liver has 500+ known functions. 124 Liver Makes blood clotting factors Makes blood proteins (albumin) Makes bile Regulates glucose levels Processes fats Makes cholesterol Processes amino acids Detoxifies chemicals 125 Liver It is also the only organ that can regenerate. As much as 80% of your liver could be cut away and it would grow back to a full size in approximately three months. With only 1/6th of your liver present your body could continue to function. It is usually hard to determine if the liver is damaged until the damage is quite advanced. 126 Liver It has a right and left lobe, separated by the FALCIFORM LIGAMENT. The liver gets blood from 2 sources: Artery = Hepatic artery Vein = Hepatic portal system = Blood from the spleen, stomach, pancreas, small and large intestines which all go through the liver. The nutrients that are absorbed by the GI tract go to the liver first for processing, then to the rest of the body. 127 Liver Figure 22.22 128 INTERNAL STRUCTURE OF LIVER The liver is made of hundreds of thousands of LIVER LOBULES; each one is the size of a sesame seed, giving the liver a grainy texture when you eat it. Each lobule carries out all of the functions of the liver. 129 LIVER LOBULE It has a hexagonal shape, at each corner are some vessels = HEPATIC TRIAD: – ARTERIOLE from the hepatic artery – VENUOLE from the hepatic portal vein – BILE DUCT, which goes to the gall bladder. 130 (Kupffer cells) 131 Liver Hepatic Triad: Vein, Artery, Bile Duct Figure 22.23a,132 c, d Liver Lobules 133 Liver: Central vein and sinusoids 134 Sinusoids LIVER SINUSOIDS are channels that blood can flow through. Cells that line the sinusoids are called HEPATOCYTES, and each one faces the sinusoid and is in contact with blood. The hepatocytes are what carry out all of the functions of the liver. If you made a machine to do the work of the liver, it would have to be the size of a large oil refinery. 135 Liver: sinusoids and hepatocytes 136 Function of Hepatocytes Detoxification of poisons Picking up and processing of nutrients from the portal blood – This includes picking up glucose from the nutrient-rich blood coming from the small intestine and stores it as glycogen (the storage form of glucose) for when the body needs it later. Storage of the fat soluble vitamins 137 Kupffer Cells Within the sinusoids are KUPFFER CELLS, which are macrophages. As blood flows through the sinusoids, they phagocytize old erythrocytes. The released Hgb is given to the hepatocytes, which convert it to bilirubin, one of the main components of BILE. Bile flows through a series of channels called the BILE CANNICULI to the bile duct. 138 The Liver Destroys Old Red Blood Cells By the way, when you have dark circles under your eyes, it is from hemoglobin and iron deposits from broken RBC’s that leaked out of the delicate capillaries under the thin skin there. Will skin creams remove this? 139 Problems with the Liver HEPATITIS CIRRHOSIS JAUNDICE 140 Liver Problems Infection of the liver = HEPATITIS (can be deadly) CIRRHOSIS is when the hepatocytes die and are replaced by connective tissue. This is often from alcoholism, which kills the hepatocytes. 141 Jaundice One of the symptoms from any liver disorder is a connection of the bile canaliculi and the sinusoid so some bilirubin can enter the blood. Bilirubin is yellow-green (later in its degradation it will turn brown and that is what gives the feces its color). The yellow color of bilirubin in the skin is known as JAUNDICE. 142 Jaundice Jaundice is not a disease; it is a symptom of liver disorder. It first shows up in the sclera because it is white there. The skin has other pigments, so yellow doesn’t show up as well. Newborns get jaundice from a lot of erythrocytes being broken down, and the liver gets overloaded, but it’s harmless. The treatment is UV light or sunlight, goes away in a few days. 143 144 145 146 Liver Transplant Adult-to-adult liver transplantation has been done using the donor's right hepatic lobe which amounts to 60% of the liver. Due to the ability of the liver to regenerate, both the donor and recipient end up with normal liver function if all goes well. 147 Situs Inversus Congenital condition in which the major visceral organs in the thorax and abdomen are reversed or mirrored from their normal positions. The heart is located on the right side of the thorax, the stomach and spleen on the right side of the abdomen and the liver and gall bladder on the left side. The left lung is trilobed and the right lung bilobed, and blood vessels, nerves, lymphatics and the intestines are also transposed. Situs inversus is generally an autosomal recessive genetic condition, although it can be X-linked or found in identical "mirror" twins. 148 149 Situs Inversus As long as there are no heart defects, the person has no health issues. However, donating an organ is more complicated, since the connecting blood vessels are not in the same place! People are not aware of their condition until an unrelated health issue arises, such as appendicitis, presenting on the left side instead of the right side. The doctor cannot find the heart sounds in the proper location, either. 150 40 lb Abdominal Tumor 151 Warning! The Government has issued a health warning not to swallow chewing gum. The following is a photo of what can happen: 152 153