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In & out
Digestive System
| Question | Answer |
|---|---|
| Ingestion | the act of eating. Food is fuel. |
| Mechanical digestion | much of what we eat is rather larege by cellular standards, and it needs to be broken down into smaller pieces to increase teh surface area available for the enzymes. consists of tearing, chewing and churning effects of peristalsis. |
| Peristalsis | the rhythmic contractions of our digestive organs that propel the food. two layers of muscle in the muscularis layer contract back and forth. |
| Chemical digestion | as the food travels along the digestive tract, various enzymes are released, which chemically change the complex polymers into the basic monomers that our bodies will ultimately use. |
| Secretion | It is important to note that digestive enzymes can digest your own body! Organs thus need to protect themselves by secreting various fluids. |
| Absorption | The monomers and water in the GI tract need to be transported to the body via bloodstream, but they need to be absorbed into the blood. |
| Storage and toxin processing | All of the blood from the abdominal digestive organs passes through the liver, which stores some sugar for emergency, converts other sugars into fat and breaks down toxic chemical before too much gets to the body. |
| Excretion and defecation | release of waste(feces) we do not use via the anus. |
| Main Organs of the digestive tract: My Pink elephant still smells like rotten apples | Mouth, pharynx, esophagus, stomach, SI, LI, Rectum and Anus |
| Accessory Organs | salivary glands, pancreas, liver and gallbladder |
| Layers of digestive organs | mucosa, submucosa, Muscularis, Serosa |
| Mucosa | innermost layer. Cells of mucosa produce and secrete enzymes. Provide chemical protection from enzymes as well. Layer is composed of epithelium |
| Submucosa | made of connective tissue. Lies beneath mucosa. Blood vessels and lymphatics can be found here. |
| Muscularis Externa | uses peristalsis to move food along the digestive tract. consists of layers of smooth muscle, a longitudinal layer, and a trasverse or circular layer. |
| Serosa | outermost layer. combination of connective tissue and an outermost layer of epithelial. Secretes lubricate to reduce friction. Protective layer. |
| bolus | masticated food and saliva. |
| rugae | lare folds in the lining of the gastric mucosa. allow the lumen of the stomach to expand after eating a large meal. |
| Chyme | mixture of food, saliva, and gastric juices |
| Gastrin | a hormone prodcued by the G-cells at the very bottom of the gastric pit, with increase gastric secretion(HCL) by the parietal cells. |
| enterogastric reflex | slowing of gastric contractions follows the "squirting" of chyme into the duodenum. Prevents too much chyme entering the duodenum at one, and also enables the duodenum to prepare, through the production of extra buffers, to counteract the low pH chyme. |
| 3 Phases of Digestion | Cephalic, Gastric, Intestinal |
| ulcer | occurs when stomach starts to digest its own lining. |
| How does the stomach keep from eating itself? | the gastric mucosa makes large quantities of mucus which helps to dilue the acid, thus raising/ buffering the pH of the gastric juice closet to the mucosa. |
| Chief Cells | located at the base of gastric pits, release pepsinogen, an inactive form of the enzyme pepsin |
| Parietal cells | at the neck of the gastric pits which release HLC acid. |
| How is pepsinogen activated | when it combines with HCL at the neck of the gastric pits to become pepsin. |
| greater omentum | connective tissue that hangs down from the greater curvature of the stomach in front of the small intestine, acting in part as a place for depositing excess fat, and prevents the contents from emptying into the abdominal cavity. Also contains macrophages |
| lesser omentum | connects the liver to the the lesser curvature of the stomach. Protective layer and fights against infection. |
| Parts of the small intestine | Duodenum, jejunum and ileum |
| Bile | emulsifies fat. Comes from the liver cells hepatocytes and stored in the gallbladder. |
| plicae | folds in the lining of the SI that contains thousands of fingerlike villi that contain even smaller projections called microvilli. Increase surface area for absorption. |
| lacteals | lymphatic capillary that absorbs lipids |
| large intestine | absorption of water occurs here, vitamin K absorption. pass waste from the body |
| ileocecal valve | this sphincter muscle regulates the flow of material from the ileum to the cecum |
| Rectum | the final sport for compaction of feces before deification |
| Vermiform Appendix | acts like a "good bacteria factory" that "cultivates and preserves" good bacteria nutrition to help keep your body healthy. Contains MALT. |
| What happens if the colon absorbs too much water? | constipation |
| What happes if the colon absorbs to little water? | Diarrhea |
| what makes feces brown? | urobilinogen |
| segmentation | alternating contractions. Repeated contractions at various points in the SI churn the food, allowing it to mix well with the various enzymes at work. |
| What are the three main salivary glans | parotid, sublingual, submandibular |
| saliva | cleanses the mouth, dissolves food chemicals so that they can be tasted, moistens foods and aids in compacting it into bolus, contains enzymes that begin chemical breakdown of starchy foods. |
| salivary amylase | enzyme for the digestion of starches |
| cystic duct | comes from the gallbladder. Merges with the common hepatic duct to form bile duct. |
| hepatopancreatic ampulla or sphincter of oddi | the common bile duct joins up with the pancreatic duct to form this. Releases into the duodenum. |
| Vitamin and mineral storage | iron and fat soluble vitamins are stored in the liver, to be released only when your diet doesn't have enough. |
| cholecystokinin or CCK | duodenal hormone, which causes the release of pancreatic enzymes. |
| enzymes | large proteins with an active site where the substrate, or molecule to be digested fits. Speeds up reaction. |
| Function of GI System | is to digest food and absorb nutrients, salts and water. |
| Digestion | process of breaking down food into components that can be asorbed |
| Absorption | is the movement of nutrients, salts, and water accross the GI epithelium into blood or lyph |
| villi | Fingerlike projections of the small intestinal mucosa that tremendously increases its surface area for absorption |
| Microvilli | contained within the villi. They greatly increase the surface area of absorptive membrane. |
| Propulsion | second phase of digestive process. food moves through the GI tract after swallowing by means of peristalisis; alternate waves of contraction and relaxation of of muscles in the organ walls. |
| What are the six processes of digestion | 1. Ingestion, 2. Propulsion, 3. Mechanical digestion, 4. Chemical digestion, 5. Absorption,6. Defecation. |
| What is the site of ingestion? | The mouth |
| Which essential digestive activity actually moves nutrients from the outside to the inside of the body? | Absorption. |
| What Sensors in the GI tract are stimulated, they resond via feflexes. What types of digestive activity may be put inot motion via those reflexes? | Reflexes associated with the GI tract promote muscle contration and secretion of digestive juices or hormones. |
| Many of the controlling systems of the giestive system are intrinsic. True or False? | True:nerve plexuses or hormone producing cells are between the muscle layers in the walls of the alimentary canal (gut brain). They influence eacher both in the same and in different digestive organs. |
| Short reflex | Internal GI tract stimuli: are mediated entirely by the local enteric or "gut" plexuses in repsone to stimul arising insidethe GI tract. Example: Stretch reflexes of stomach and chemoreceptors. |
| Long Reflexes | stimuli inside or outisde the Gi tract and invovles CNS and extrinsic autonomic nerves: Example of extrinsic: sight, smell, taste, thought of food. |
| gut brain | Refers to the enteric nervuous system of the digestive organs |
| Visceral peritoneum | covers the external surfaces of most digestive organs |
| parietal peritoneum | lines the body wall |
| peritoneal cavity | a slitlike potential space containinga slippery fluid between teh parietal and visceral peritoneum. |
| Mesentery | double layer of peritoneum. provide routes for blood vessels, lymphatics and nerves to reach digestive viscera;hold organs in place and store fat. |
| Serous cells | produce watery secretion containing enzymes, ions and a timy bit of mucin. Produced by salivary glands |
| mucous cells | produce mucus. |
| What is the role of the tongue? | prepare food for swallowing, speech, and taste. |
| What is the composition of saliva? | contains largerly water 95-97. Slightly acidic 6.75-7.0 Includes electorlytes, digestive enzymes(salivary amylase and lingual lipase), proteins mucin,lysoyzyme and IGA. |
| lysozyme | bactericidal enzyme that inhibits bactera growth in the mouth and may help to prevent tooth decay. |
| Passage of food through the pharynx | from the mouth food passes posterioly into the oropharynx and then the laryngopharynx into esophagus. |
| Heartburn | burining, radiating substernal pain that occurs when the acidic gastric juice regurgitates into the esophagus. Occurs when a person has eaten or drunk to excess which forces abdominal contents upwards. |
| hiatal hernia | common with heartburn, the superior part of the stomach protrudes slightly abouve the diaphragm. This is often due to an abdnomral relaxation or weakening of the gastroesophgeal sphincter. |
| Name four antimicrobial substances found in saliva. | lysozyme, fefensins, cyanide compuounds, and IgA antibodies. |
| What is the importance of the serous portion of saliva | The serous portion of saliva is rich in salivary amylase, an enzyme that chemically breaks down starch. Helps to hydrate the foodstuffs and help provide protection aganist microorgansims. |
| How is Salivation controlled | by the parasympathetic division of ANS. |
| What is the functional significance of the epithelial change seen at the esophagus stomach junction | The esophagus is merely a chute for food passage and is subjected to a good deal of abrasion, which a stratified squamous epithelium can withstand. The stomach mucosa is a secretory mucosa served well by a simple columnar epithelium. |
| What role does the tongue play in swallowing? | The tongue mixes the chewed food with saliva and compacts the food into bolus. |
| How are the respiratory passwages blocked during swallowing? | During swallowing the larynx rises and teh epiglottis covers its lumen so that foodstuffs are diverted into the esophagus posteriorly. |
| Deglutition | process of swallowing. 2 phases (bucal) & Pharyngeal-esophegeal. Voluntary and an involutary. |
| mucous neck cells | found in the upper regions of the gastric glands. Secrete mucus. |
| Enteroendocrine cells | located deep in gastric glands. release histamine and sertonin. |
| What structural modification of the stomach wall underlies the stomach's ability to mechanically digest food? | The stomach has three layers of smooth muscle-longitudinal,circular, and oblique. Addition of the oblique layer allows the stomach to pummel food in addition to its peristalic movements. |
| Two substances secreted by cells of the gastric glands are needed to produce the active protein digesting enzyme pepsin. What are these substances | The chief cells produce pesinogen, which is the inactive pepsin enzyme, and the parietal cells secrete HCL needed to activate pepsinogen. |
| What protective substances or activities makes up the so called mucosal barrier? | The mucossal barrier consists of epithelial cells of the mucosa are joined by tight junctions, thick coating of bicarbonate rich mucus is built up and the quick replacement of dead or dying cells by stem cells. |
| Intrinsic factor | Secreted by the stomach.Required for intestinal absorption of vitamin b12, to produce mature RBC. In absence pernicious anemia results. |
| Cholecystokinin(CCK) | produce in duodenal mucosa. Stimulus for production is the prescence of fatty chyme. Target organ is liver/pancreas. Increases output of enzyme rich pancreatic juice. Stimaulates gallbladder to release bile |
| Gastric Inhibitory peptide (GIP) | Produced in Duodenal mucosa. Produced in the presence of glucose, fatty acids, and amino acids in SI. Target organ is stomach and beta cells of pancreas. Stimulates insulin release and ihibits HCL production. |
| Gastrin | Produced in the stomach mucosa (g cells). Produced in the presence of food.Target organ is SI,stomach, LI,illeocecal valve. Stimulate contration of the the intestinal muscle. Increases HCL secretion. Stimulates gastric empyting. Stimulates mass movement. |
| Motilin | Production in Duodenal mucosa. Production occurs during fasting; perodic release everyone 1.5-2hrs. Stimulates migrating motility complex in proximal duodenum |
| migrating motility complex | are waves of activity that sweep through the intestines in a regular cycle during fasting state. "Growling" in stomach sound |
| Secretin | produced in duodenal mucosa. produced in the presence of acidic chyme. Inhibits gastric gland secretion and gastric motility during gastric phase of secretion. Increase output of pancreatic juices. Increases bile out put. |
| How does the presence of food in the intestines inhibit gastric secretion and motility? | The presence of food in the duodenum inhibits gastric activity by triggering the enterogastric reflex and the secretion of certain hormones. |
| enterogastric reflex | reflex that inhibit the vagal nuclei in the medulla, inhibit local reflexes and activate sympathetic fibers that cause pyloric sphincter to tighten and prevent further food entry into the SI. Trigger release of enterogastrone(hormones) |
| enterogastrones | are hormones that include: secretin, CCK, and VIP. all inhibit gastric secretion. |
| what common advantage do circular folds, villi, and microvilli provide to the digestive process? Which these modifications causes chyme to spiral through the lumen and slows its passage? | All of these modifications increase the surface area of the SI. The ciruclar folds force the chyme to spiral through the lumen. |
| What are bush border enzymes? | brush border enzymes are enzymes associated with the microvilli of the Small intestine mucosal cells. Examples are Glucoamylase (Maltase) Sucrase-Isomaltase Lactase Peptidases |
| What is the lacteal and what is its function? | A lacteal is a blind ended lymphatic capillary that picks up lymph, which is returned to the blood. |
| Name three secretory products that help to protect the intestinal mucosa from bacterial damage | IgA, HCL, defensins, and lysozyme protect the intestinal cells from bacterial damage. |
| What is a portal triad? | A portal triad is a region at the corner of a hepatic lobule that contains a branch of the hepatic portal vein, a branch of the hepatic artery and the bile duct. |
| What is the importance of the enterohepatic circulation | The enterohepatic circulation is important recycling mechanism for retaining bile salts needed for fat absorption. |
| What is the role of the kupffer cells of the liver? | Kupffer cells are macrophages that rid the blood of bacteria and dead cells. |
| Maryanne has pancreatitis and her pancreas is swollen and temporarily unable to produce pancreatic juice. What type of foods stuffs will probably not be digested until she recover? | The pancreas is the only important source of lipases, so fats will probably not be digester or absorbed during her illness. |
| What is the functional difference between pancreatic acini and islets? | pancreatic acini produce the exocrine products of the pancreas( digestive enzymes and bicarbonate rich juice). The islets produce pancreatic hormones, most importantly insulin(beta) and (alpha) glucagon, and somatostatin (delta) |
| What stimulates CCk release and what are its effects on the digestive process? | CCk is secreted in response to the entry of chyme rich in protein and fat in the duodenum. It causes the pancreatic acini to secrete digestive enzymes and stimulates the gallbladder to contract to release bile. |
| What is the makeup of the fluid in the pancreatic duct? In the cystic duct? In the bile duct? | Fluid in the pancreatic duct is bicarbonate-rich, enzyme rich pancreatic juice. Fluid in the cystic and bile ducts is bile. |
| Pancreatic enzymes | trypsinogen, chymotrypsinogen, procraboxypeptidase, amylase, lipases, nucleases. |
| Pancreatic proteases | pancreatic enzymes that break down protein. trypsinogen, chymotrypsinogen, procraboxypeptidase |
| Distension of teh stomach and duodenal walls have different effects on stomach secretory activity. What are these effects? | Distension of the stomach walls enhances stomach secretory activity. Distension of the walls of the SI reduces stomach secretory activity. |
| Which is more important in moving food along the small intestine-peristalsis or segmentation? | Segmentation. |
| What is the MMC and why is it important. | MMC is the migrating motility complex, a pattern of peristalsis seen in the SI that moves the last remnat fo a meal plus bacteria and other debris into the large intestine. |
| Mass movements | are long, slow moving, but powerful contractile waves that move our large areas of the colon three or four times daily and force the contents toward the rectum. |
| What propulsive movements are unique to the Large intestines? | Mass movement. |
| What is the result of stimulation of stretch receptors in the rectal walls? | Activation of stretch receptors in the rectal wall initiates the defecation reflex. |
| In what ways are enteric bacteria important to our nutrition? | Enteric bacteria synthesize B vitamins and most of the K the liver needs to synthesize clotting process. |
| What type of chemical reaction is the basis of all enzymatic food digestion? | All food digestion depends on hydrolysis reactions |
| Fill in the blank. Amylase is to starch as _ is to fats. | lipase |
| What is the role of bile salts in the digestive process? In Absorption? | bile salts emulsify fats so that they can be acted on efficiently by lipase enzymes and form micelles that aid fat absorption. |
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