Chapter 23 Digestive system
Describe the normal movements of the large intestine, including the developterm-16ment of diarrhea and how it relates along with the absorption of water.
Cecum is the entrance of the large intestine sends chyme up to ascending colon then the transverse and then to the descending colon. The introduction of bacteria in the colon will irritate the If you have inflammation in the large intestine or inflammation the large intestine will not be able to abrob the water which will create watery stools. This will form diarrahia
Identify the accessory organs of the digestive system and briefly list their primary (digestive) functions.
Digestive secretion Accessory digestive organs are the teeth, tongue, gallbladder and a number of large digestive glands - the salivary glands, liver and pancreas Bolus - mass ball - gets broken down through digestive system
List the components of gastric juice (including from which cells they arise), and explain the function of each component.
Kill any pathogens keep food moving along the way Creates chyme - semi liquid paste Hydrochloric acid Water/minerals, intrinsic factor, hormones Glands are made up of cells Mucus cells - create mucus chief cells - create pepsinogen - inactive form of pepsin. To make active you need hydrochloric acid parietal cells - secrete a lot of hydrochloric acid. This activates pepsinogen Intrinsic factor - very important because it binds to vitamin B12 to allow absorption of nutrients in SI. You can eat all the food you want but if this is not working you cannot extract nutrients from food Hormones located in the small intestine Gastrin and histamine - involved heavily HCL secretion Serotonin - amino acid somatostatin - inhibits HCL secretion (party pooper - stops everything)
Identify the primary anatomy (and related) functions of the mouth, focusing on the components and digestive functions of saliva
oral cavity lips, cheeks - keep food between your teeth teeth - mechanical breakdown - large pieces into smaller pieces tongue forms Bolus is formed from chewing hard palate - top of mouth - friction for chewing Soft palate - assist with swallowing Bolus Tonsils - immunity Mucosal tissue - protect against pathogens salivary glands - secrete saliva to mouth for chemical breakdown Parotid - by ear, submandibular - jaw, sublingual gland - sits under tongue The saliva is mainly composed of water, electrolytes that make it slightly acid. Also has enzymes amylase (breaks down carbs) and lipase (breaks down lipids) - saliva facilitates taste, begins chemical digestion, forms bolus and kills microorganisms sympathetic control - digestion sloes down
Describe the normal movements of the small intestine via the ileocecal sphincter.
****small intestine absorbs all nutrients Going from small intestine to large intestine there is another door - ileocecal spincter. This falls under gastroileoal reflex. Segmentation cause ileocecal spincter to open and push food over
List and identify the 3 structures of the small intestinal mucosa that are mterm-23odified to increase the absorptive surface area. Explain how these structures allow for digestion or absorption of nutrients.
1. Villi- a lot of capillary beds and lacteals - small fingerlike projections. 2. Microvilli - brush border cells (small cells) - They increase surface area-Allows for maximal absorption - break down the last parts of your carbohydrates 3. Instestinal crypts - spaces - lining - endocrine cells - CCK and secretin The lining of your small intestine is set up for the absorption with these cells Chyme moving through small intestine - mixing with bile, pancreatic juices - does a lot of mixing via segmentation (back and forth motion). After that is peristalisis - whatever is left gets sent to large intestine Small intestine is where you are absorbing most of your food
Identify the major organs of the alimentary canal and briefly list their primary functions.
AKA GI tract, mouth and ends at the anus Long muscular tube modifies itself into different structures mouth (ingestion, chewing), pharynx carries food to stomach, esophagus - peristalsis. carries food to stomach, stomach - , large intestine, small intestine, anus oropharynx - swallowing - propulsion Stomach - churning and peristalsis small and large intestine - digestion and absorption. small intestine connects to lymphatic system anus - defecation
List and explain the general functions of the large intestine.
Another name for the large intestine is the colon. It is larger in diameter. It also has a lot of gut bacteria, this bacteria breaks up anymore of undigestable food to monomeric form. Example is complex carbohydrate - cellulose (undigested part) will break down in large intestine and release methane and sulfur. Synthesizing necessary vitamins B and K - B12 is very important because intrinsic factor needs to bind vitamin B 12 in order for you to be able to be able to absorb the nutrients. If you don't do that you can take in all nutrients you want but you can't absorb it Vitamin K is involved in blood clotting A lot of water reabsorption is taking place in the large intestine As you are moving indigestible food food going from the small intestine over to large intestine - chyme is moving slowly - water is reabsorbed and you are left with solid Can sit in large intestine for up to 10 hours and is eventually secreted in the form of feces
List the enzymes found in pancreatic juice, and explain the function of each enzyme.
Bicarbonate Pancreatic amylase responsible for breaking down carbohydrates in the small intestine Pancreatic lipase - breaks down lipids Pancreatic nuclease - breaks down nucleic acid into monomeric form - DNA and RNA
What type of feeders are we?
Bulk
Explain how gastric secretions are regulated (3 phases). Include the source and effects of gastrin, as well as the enterogastric reflex and how CCK and secretin affect gastrin.
Circular musculars do segmengtation Phase 1 cephalic - reflex ( sensory input to Cerebral cortex) release with sensory in put - seeing food, smelling food, tasting Phase 2 - gastric (Happens in stomach) Acidity maintained at 2-3 breaking down distension - creating peptides, Gastrin enter G cells Acetylcholine increases HCl release Phase 3 Intestinal (Intestine) intestine releases release gastrin an Secretin - enough with the gastrin Cholecystokinin
Outline the mechanism of deglutition (aka swallowing).
Deglutination - Swallowing begins in esophagus involuntary reflex - epiglottis protects airway from food entering in buccal phase pharyngeal-esophageal phase Pharyngeal-esophageal phase continued Peristalsis moves food through esophagus through to the stomach gastroesophageal sphincter surrounding cardial orifice opens after food enters the stomach, the sphincter closes preventing regurgitation.
Outline the general effects of parasympathetic and sympathetic impulses on the alimentary canal via the enteric nervous system.
Enteric - in house nerve supply of the alimentary canal. Stretch receptors - reflexive system - controlled by smooth muscle. Chemical imbalances that get sent back to the brain. Senensory info gets carried by submucosal nerve plexus and myenteric nerve plexus - lay between circular and longitudinal muscle layers of the muscularis externa. intervating epithelium to the brain Parasympathetic - currently under during - digestion speeds up - Sympathetic - workout - digestion slows down or fight or flight.
Outline the defecation reflex.
Initiated by presence of food Once the food is in the rectum and reaches the anus there is a reflex that allows for the rectal to stretch and colon and rectum both contract together to allow for your spincters (internal and external) When that happens your internal spincter which is made up of smooth muscle and is involuntary And then the external is going to be voluntary cause it is made up of skeletal muscle. Once chyme is in the anal canal - process of elimination is controlled by 2 spincters Internal and external spincters As haustra move food it moves it as a mass - slow peristalsis propelling food forward.
List and describe the basic structure and function of the four layers of the wall of the alimentary canal.
Muscle layers - muscles externa Chief cells (Pepsin) and parietal cells (HCl - hydrochloric acid) Mucosa - absorption and secretion/protection (MALT) - simple columnar epthithelim- inner mucosa - hormone and enzyme secretion - the MALT is immune system immunity protection Submucosa - blood vessels protruding, blood, lymph and nerve supply Muscularis externa - 2 layers - circular layer (segmentation), longitudinal layer (peristalsis) Serosa - outer most layer - simple squamous
Explain how pancreatic and bile secretions are regulated via the functions of cholecystokinin and secretin.
Pancreas - insulin and glucagon system Pancreatic juice is made - heavily rich in enzymes trypsin chymotrypsin - breaks down protein Bicarbs = more basic pancreatic amylase - responsible for breaking down carbohydrates in the small intestine Pancreatic lipase - responsible for breaking down fats and lips Nucleases - break down amino acid into monomeric form DNA and RNA No digestion = closed spincters No chyme = No juices ... need to have food present for secretion 1st door - esophageal spincter 2nd Pyloric spincter by the dueodenum CCK and Secretin inhibit gastrin secretin (HCl) Secretin promotes production of bile production of the liver and bicarb production in the pancreas - will cause secretion into duodenum CCK - tell pancreas to secrete juices and also cause the gallbladder to secrete bile through common bile duct into duodenum and bein chemical digestion As soon as we send chyme over - empting contents into dueodenum you have entero endrine cells that sit on the walls. What they do - they release secretin and CCK. They travel in the blood and go to liver to tell liver to make bile - and tell gallbladder to contract to secrete stored bile over into small intestine, go to the pancreas and tell it to secrete pancreatic juice that is rich in enzymes, and then they will tell the stomach to stop making gastrin so it is not acidic
Summarize the digestion and absorption of the following nutrients:a.Carbohydrates: a. dietary carbohydrate variations, organs and associated enzymes involved with digestion, absorption via secondary active transport in small intestine b.Proteins: organs and associated enzymes involved with digestion, absorption via secondary active transport in small intestine c.Lipids: organs and associated enzymes involved with digestion, emulsification, and functions of micelles and chylomicrons in absorption into lacteal
See chart - know where all food sources are broken down
Distinguish between mixing movements (segmentation) and propelling movements (peristalsis) and state what type of muscle allows for each type of movement.
Segmentation - circular layer - move food back and forth - allows food to break down even more Peristalsis - rythmich involuntary contraction propelling food into digestive tract Bolus - rounded mass of chewed of food - Muscul;ar externis
State the function of the gallbladder.
Stores and releases bile into the duodenum through the cystic duct
Describe the structure (gross anatomy) and overall functions of the stomach. Gross anatomy includes: cardia, fundus, body, greater/lesser curvature, pylorus, pyloric sphincter, rugae.
Vagus nerve - swallowing and initiating thatfundus cardia - surrounds cardial orifice through which food enters the stomach from the esophagus fundus - dome shaped part tucked beneath the diaphragm that bulges suprolaterally to the cardia. Most of chemical breakdown of the food takes place here greater/lesser curvature - greater is the lateral surface, lesser is medial surface pylorus - continuous with duodenum through pyloric sphincter pyloric sphincter - valve which controls stomach emptying or filling. Must open for food to enter rugae - allow stomach to extend 80X, internal folds - hold 4 liters of food
Describe the composition of bile, focusing on the function of bile salts.
watery green substance Bile salts - acidic and can surround the lipid to breakdown
Describe the gross anatomy of the large intestine, including: cecum, colon (ascending, transverse, descending), haustra, rectum, anal sphincters.
Large intestine is also know as the colon. Large intestine is broken up into 3 parts 1. Cecum - entrance Appendix is where MALT is located, protecting from invaders. Can live without appendix. If appendix gets inflamed, appendicitis happens. Also stores resident bacteria 2. Large intestine aka colon (ascending, transverse and descending) Large intestine have pouches have pouches called haustra that help food move up. Haustra contract and allow chyme to move up and transfers through colon - slow segementation promoting water reabsorbtion ascending colon - transverse colon - descending colon - 3. Once chyme is in the anal canal - process of elimination is controlled by 2 spincters Internal and external spincters
List and explain the metabolic and digestive functions of the liver.
Largest gland in the body, stores vitamins A, D, E and K K - blood clotting) - , sugar and glycogen falls under metabolic functions of the liver. converting glucose into glycogen for storage Nutrient rich blood is getting processed through hepatic portal vein/duct Major detoxification takes place here, ammonia, medication, alcohol Digestive function. Bile is made in the liver - watery greenish substance - made to break down fat. Bile salts which breaks down fat and recycling them - puts them in lactels and capillary beds. Bile pigments - Billy ruben Cholesterol - HDL and LDL When bile is made it gets transported to the gallbladder for storage. When performing chemical digestion in small intestine gallbladder contracts releasing bile. Sends bile to duodenum making it less acidic compared to the stomach. Bile Transferred from liver to the gallbladder for storage via hepatic duct and cystic duct Bile Transported by gallbladder to duodenum through common bile duct
Where do Carbohydrates, lipids, proteins and nucleic acids
Mechanical digestion - oral cavity - mouth - salivary amylase, starch and 1 se carbohydrates Chemical digestion - stomach and small intestine Carbohydrates - mouth amylase Protein - Small intestine Nucleic acids - small intestine Put back in hepatic portal vein gets detoxified and sent to tissues for growth Exception are Lipids - Enter in lymphatic system via lacteals. Dropped off at tissues and they stay there forming adipose tissue to be used for fuel. Mechanism 1st consume fats - bile salts secreted by liver that emulcifies fat turning it into fat globules. And then the fat globule get broken down by pancreatic lipase - its going to break in down to free fatty acid and glycerol. That turns into turns into small aggregates - call micelles - aggreagate fat globules mixed with chyme. once they become these they become vehicles to transport them to the small intestine Micelles cross epithelial cells of the small intestine - once they cross they turn back into to trigylcerides From triglycerides they get packaged by Golgi apparatus into small packages called chylomicrons - chylomicrons fuse with the lining forming exocytosis to get to the lacteals then get carried to tissue and blood. The rest will get stored as adipose tissue. Remainder gets transported as cholesterol (HDL and LDL) ***** Non polar does not require much effort they diffuse Polar will require a carrier protein Know chart in the slides A. Carbohydrates - moreaks down the polysaccharide uth, salvatary amylase, polysaccharides and disaccaraides transported to stomach then dueodumen where a lot of mixing takes place with bile and pancreatic juice and then pancreatic juice - pancreatic amylase breaks down polysaccharide into disaccharides then that is sent to small intestine where disaccharides are broken down into monomers - monosaccharides B. Protein - the only ones that break down in the stomach - due to pepsin. Inactive form of pepsin is pepsinogen in the stomach reacts and breaks down to polypeptides. HCl turns pepsinogen on to become active pepsin. Once you have pepsin your proteins get broken down just a little bit becoming small, they become polypeptides that get sent to the duodenum, that's when other enzymes get activated. pancreatic enzymes cleave bonds adjacent to amino acids turning them into peptides. Carboxypeptidase breaks peptides into amino acids. They are further broken into their monomeric forms and are absorbed by the epithelium of the small intestine. C Lipid - do not get broken down until the small intestine. A little gets broken down in the duodenum by the bile salts (lipase) breaking down to pre fatty acids and triglycerides - will eventually break down in the small intestine monoglycerides. bile produced by the liver is stored in the gallbladder - gets released through crystal - reacts with fat to form fat globule. - micelles cross into small intestine and form triglycerides. Send to Golgi apparatus get packages into chylomicrons sent out via exocytosis into lacteal ****** No digestion takes place in the esophogus Know micelles, why it gets turned into triglyceride and what chylomicrons are
List and explain the functions of the small intestine.
Small intestine composed of 3 parts (long coiled tube): 1. Duodenum (sits right below stomach, directly connected to stomach - pyloric spincter - opens up allowing stomach to empty chyme) 2.Jejunum 3. ileum Receives accessory organ secretions, a lot of bile, pancreatic juices mixing in with chyme - not very acidic anymore - becomes more basic here - bicarbonate in pancreatic juices gastrin gets secreted by G cells get inhibited because of secretin, CCK because you no longer need HCL to be there anymore complete digestion - because major macromolecules carbs, lipids, nucleic acids and proteins all get digested into monomeric basic structure complete Nutrient absorption Smaller structure that increase surface area to harvest and absorb nutrients
State the digestive function of the pancreas.
accessory organ - secretes insulin and glucagon levels - important role in digestion Pancreatic juice - heavily rich in enzymes. Trypsin, chymotrypsin and carboxypeptidase which all break down PROTEIN pancreatic juices have bicarbs - contrast going on with stomach - more basic to mix with chyme Pancreatic amylase responsible for breaking down carbohydrates in the small intestine Pancreatic lipase - breaks down lipids Pancreatic nuclease - breaks down nucleic acid into monomeric form - DNA and RNA Secretes juice into duodenum
