The Digestive System GN PDF

The Diges)ve System Biomedical Science Coralie Frances GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their applica;on to pa;ent management 1.1.6 Describe relevant and appropriate physiology and explain its applica;...

The Diges)ve System Biomedical Science Coralie Frances GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their applica;on to pa;ent management 1.1.6 Describe relevant and appropriate physiology and explain its applica;on to pa;ent management Intended Learning Outcomes By the end of the session you should be able to: Describe the organs of the diges;ve system Explain the func;ons of the major organs of diges;on Describe the types of ;ssue and linings associated with the diges;ve organs List the func;ons of gastric juice Summaries the chemical diges;on of food Why is diges)on part of the curriculum? As student Dental hygienists and therapists why do you need to learn about the structure and func;on of the diges;ve system? Why do you think it is important to understand the learning outcomes in this lecture? Mouth is start of digestive tract Role of saliva and effect of lack of saliva may have Assess your knowledge pre lecture What are the Ive main ac;vi;es that take place in the diges;ve system? Look at the next slide Can you name the component parts of the alimentary canal labelled 1-10? Answers The processes are: Of digestive system 1. Inges)on 2. Propulsion 3. Diges)on 4. Absorp)on 5. Elimina)on (defaeca)on) Name the component parts of the alimentary tract labelled 1 – 10 1. Mouth 2. Salivary glands 3. Gall bladder 4. Liver 5. Pancreas 6. Small intes;ne 7. Oesophagus 8. Stomach 9. Large intes;ne 10. Rectum How did you do? Rate your knowledge on a score of 1-5 (1 least knowledge; 5 greatest knowledge) Con;nue with the PPT to refresh your knowledge then answer the same ques;ons again What are your scores now? Useful References Waugh, A. and Grant, A. (2018) Ross & Wilson Anatomy And Physiology In Health And Illness. 13th ed. Elsevier. Ward, J. and Linden, R. (2017) Physiology At A Glance. 4th ed. Wiley-Blackwell. What happens to the food you eat? Order of lecture The structure & func;on of each organ will be described chronologically at each stage as the food reaches it www.visitgreenwich.org.uk/food-and-drink Alimentary Tract Also known as alimentary canal/ gastrointestinal tract/ digestive tract Alimentary tract – a tube that extends from mouth to rectum As food moves through the canal, it is ground and mixed with various diges;ve juices  Absorbed and distrubuted to the all the tissues by the blood. Alimentary tract func)on Converts food into small, nutri;onal molecules for absorp)on and distribu)on by circula;on to all ;ssues of the body, and excretes the unused residue The ac;ve processes are: Inges)on Propulsion Diges)on Absorp)on Elimina)on (defaeca)on) Taking in of food and drink Mixes and moves contents along tract Mechanical breakdown of food, chemical digestion by enzymes Digestive food substances pass through digestive system walls into blood and used by body cells Excretion of waste protucts Alimentary Tract Func)on Inhabited by many microorganisms - balance between immunity and tolerance Stomach lining -secretes hydrochloric acid - ideal conditions for protein digestion enzymes to work - kills bacteria to protect body. It is also part of immune system: Mucus (IgA), Low pH lysozyme Enzymes (saliva, bile) (Saliva poisonous in some animals to quieten down living prey!) Components of diges)ve system Composed of the following parts: The gut – The small and The mouth oesophagus The stomach The rectum Large intes;nes Accessory organs Do not actually move food throughout the body Involved in processes in digestion, ingestion and absorption The The liver The The gall pancreas bladder salivary glands  General structure of the alimentary tract Layers of the walls follow a consistent pattern form the Oesophagus onwards Walls of the diges)ve tract consist of four layers throughout its length Adven))a/Serosa - outer covering of connec;ve ;ssue Muscularis - smooth muscle that provides contrac;ons (peristalsis) to move food consists of two layers, out layer longitudinal, inner-circular Submucous - loose connec;ve ;ssue contains blood vessels, lympha;c vessels, nerves and glands Mucosa - lining epithelial layer coated with mucous  Revision ques)on? What are the 5 ac;vi;es which take place in the alimentary canal? Can you describe them? Ingestion - taking in of food or drink Digestion - breakdown of food - mechanical and chemical Propulsion - mix and propel food Absorption - Digestive food substances pass through digestive system walls into blood and used by body cells Elimination - Excretion of waste products  Teeth break down food into small pieces with aid of tongue - voluntary muscles Shapes food into bolus In the Mouth - Mechanical During swallowing - soft palate and uvula move superiority upwards to close off nasopharynx to prevent food entering nasal cavity. If this fails - nasal regurgitation occurs - may occur in people with neuromuscular disease Teeth - To tear, rip and chew food to physically break it into smaller pieces and produce a bolus Uvula- Stops food or liquid entering nasal cavity Tongue - Voluntary muscular structure important in mas;ca;on and deglu;;on  Mouth - mechanical and chemical Salivary amylase - break down of food - enzymes In the mouth - Chemical Salivary amylase (ptyalin) breaks down polysaccharides, starch in the bolus to maltose, a less complex sugar (start of diges;on) Large par;cles like starch cannot be absorbed into small intes;ne Taste buds allow apprecia;on, also sample poten;al hazards  After mastication, food is formed into bolus Salivary secreted by glands in mouth moisten the food to aid in swallowing Salivary enzymes begin process of digestion Bolus A round or oval shaped mass of food formed in the mouth aeer thorough chewing, in prepara;on for swallowing Food is crushed, ground by teeth – mas$ca$on Salivary glands secrete saliva which makes food moist and easy to swallow (stuck together with mucin) as well as containing enzymes that commence diges;on  Exocrine glands -ducts through which the saliva is secreted. Salivary Glands (3 pairs) Submandibular A at the angle of the jaw opens into the goor of the mouth, source of 70% of saliva Sublingual B in front of the submandibular pair and opens into the goor of the mouth, source of 5% of saliva Paro)d C below the external acous;c meatus the duct opens into the mouth opposite the buccal of second upper molar, source of 25% of saliva Saliva D 99.5% is water and only 0.5% other substances (mucus a and diges;ve enzyme called salivary amylase which begins the diges;on of carbohydrates)  1st phase of swallowing is voluntary Swallowing The tongue forces food in pharynx Next stage is involuntary - tongue blocks mouth and soft palate rises to close nasopharynx - larynx rises to that epiglottis closes off trachea to prevent food entering lungs Bolus move along pharynx and oesophagus by peristalsis - relaxation/contractions create wave like movement that push bolus forwards. Involves co-ordinated ac;vity of tongue, soe palate, 1 pharynx and oesophagus 2 First phase is voluntary as food is forced into the pharynx by the tongue 3 Aeer this, swallowing is a re2ex process Tongue blocks the mouth, soe palate closes nose and 4 larynx rises so that epiglois closes oj trachea Food moves into pharynx and 5 onwards by peristalsis Video of swallowing hkps://www.bing.com/videos/search?q=video+of+swallow+anatomy&ru=%2fvideo s%2fsearch%3fq%3dvideo%2520of%2520swallow%2520anatomy%26qs%3dMM%2 6form%3dQBVR%26sp%3d2%26ghc%3d1%26pq%3dvideo%2520of%2520swallowin g%26sk%3dMM1%26sc%3d2-19%26cvid%3d7492F7227E984C7C9811A7634E7F469 9&view=detail&mid=81EC2DB5BDE9964A8EC081EC2DB5BDE9964A8EC0&rvsmid= BDAFC53EBDE8FEE9E496BDAFC53EBDE8FEE9E496&FORM=VDQVAP  Located in Three stages of swallowing of bolus  GI tract from mouth to stomach = oesophagus Oesophagus Swallowed bolus travels from mouth to stomach via a muscular tube, the oesophagus About 25cm long, it is the Irst part of the diges;ve tract proper Oesophagus: - Lined with mucus membrane - Secretes guid to lubricate downward movement of food - Smooth muscle wall contracts to squeeze food towards stomach  Series of wave like muscle contractions Propels food through digestive tracts through relaxation/contraction of circular and longitudinal smooth muscles Bolus enters stomach through oesophageal sphincter Peristalsis Rhythmic contrac$on of smooth muscles propels contents through diges;ve tract Waves – circular contrac;on occurs behind bolus to prevent backwards movement, followed by contrac;on of longitudinal smooth muscles to push bolus forwards Bolus enters stomach to become chyme More diges)ve tract movements Segmenta)on: A muscular movement in the small intes;ne Periodic constric;on of segments of intes;ne without movement backwards or forwards A mixing rather than a propulsive movement Vomi)ng: Propulsion comes from contrac;on of abdominal muscles- peristalsis does not reverse in the oesophagus Ques)ons? What is formed during Bolus mas;ca;on, ready for swallowing? What assists this to be Salivary enzymes and mastication formed? What needs to be closed oj Nasopharynx by uvula before swallowing takes and soft palate place? Trachea by larynx and epiglottis Ques)on? What is the func;on of the smooth muscle found in the wall of the oesophagus? Contracts to push bolus downwards  Food enters mouth - bolus - enters oesophagus - leaves through oesophageal sphincter into stomach Leaves through pyloric sphincter into small intestine. Stomach Secretions of gastric juice containing hydrochloric acid - causes stomach to be highly acidic environment Hollow muscular organ, J-shaped, lee Fundus, body and side of the abdominal pylorus recognised as cavity (liver is on the dis;nct regions right) Pyloric sphincter - separates stomach from small intes;ne Highly acidic Oesophageal sphincter environment - separates stomach from oesophagus  Lining stomach - highly specialised Structures of the Stomach The lining of the stomach has numerous folds when empty called rugae; they allow for expansion when we eat Has numerous gastric glands that secrete “gastric juice” into the stomach The most common cells found in the glands are: Parietal cells – produce HCL acid that denatures proteins. Hydrochloric Chief cells – produce pepsin that begins protein diges;on Mucus cells – produce mucus that protects from Hydrochloric ac;on  Glands secrets enzymes which produces proteins Stomach lining And hormones that stimulate acid production and stomach motility Majority of absorption occurs in small intestine Some absorption occurs from stomach such as some water and alcohol. Epithelium forms deep pits which can contain glands Hormones – e.g. gastrin which increases Hall secre;on and stomach mo;lity Glands secrete enzymes, hormones and mucus Stomach absorbs some water, lipids, cajeine, alcohol Enzymes – e.g. pepsinogen → pepsin, necessary for protein diges;on  Parietal - gastric glands of stomach lining secrete hydrochloric acid Sec)on through stomach lining Enteroendocrine cells - secrete CCK Specialised cell found within GI tract, stomach and pancreas - produce and release hormones in response to a number of stimuli. Hormones may be released into blood stream to produce systemic effects and can be distributed as local messengers. Secrete thick layer of mucous to protect lining from digestive juices ↑  Rugae folds expand when stomach fills with food Func)ons of the Stomach Temporary storage area for food (3-4 hours) which is also churned by And mixed with digestive juices and enzymes muscular layers to form chyme, a creamy substance voided via pyloric sphincter to duodenum Muscles relax and contract to aid mechanical breakdown Surface area increased by rugae Pyloric sphincter holds food in stomach allows for emptying of chyme into small intes;ne Stomach - digestive juices formed by gastric glands - secretes include enzyme pepsin which breaks down proteins and hydrochloric acid. Chyme passes through pyloric sphincter into first part of small intestine. Ques)ons What is the food called Chyme within the stomach? Oesophageal What is the name of sphincter sphincter A? A B Pyloric sphincter What is the name of sphincter B? Acidic What is the pH environment of the stomach?  Food enters mouth - bolus - enters oesophagus - leaves through oesophageal sphincter into stomach - leaves through pyloric sphincter into small intestine. Small intes)ne Main function - Aid digestion Nutrients absorbs through vili into walls Comprises: and blood stream 1. Duodenum 2. Jejunum 3. Ileum Site of majority of diges;on Jkjfg Longest part of system Usually sterile In healthy individuals - contains few microorganisms due to gastric acid  Preparation for absorption begins Duodenum First part of small intes;ne, 25 cms long Curves around head of pancreas and entry of common bile duct Chemical degrada;on of small amounts of food controlled by pyloric sphincter begins here Enzymes secreted by pancreas and duodenum itself aid diges;on of fats by emulsifying fats 2 Ducts enter Duodenum Both drain into duodenum delivering bile and pancreatic juices containing enzymes Bile duct draining gall bladder from liver Pancrea;c duct draining pancreas  Absorption of sugars, amino acids, fatty acids and any remaining nutrients that didn’t get absorbed by duodenum Jejunum & Ileum Jejunum (2metres) and ileum (3 metres) con;nue the absorp;on process of carbohydrates, proteins & fats Surface area increased by being covered in wrinkles/folds with microscopic projec;ons called villi Lined with simple columnar epithelium, the cells of the villi carry projec;ons called microvilli Large surface area available for nutrient absorp;on Villi Each villus has a capillary and a lacteal: Lacteal Capillaries absorb fat into absorb lympha;c system everything else Surface layer of columnar cells and lacteal surrounded by blood capillaries Video of role & structure of small intes)ne Ques)ons? What are the parts of the small intes;ne? Duodenum Jejunum Ileum Villi What 2 ducts enter the small intes;ne? Bile and pancreatic duct What is the major func;on of the small intes;ne apart from diges;on? Absorption of nutrients, carbohydrates and fats. Lymphatic drainage Accessory Organs Don’t directly take part in the movement of food Liver Largest solid organ and largest gland in the body Mul;func;onal Secretes bile, which accumulates in gall bladder between meals Capillaries of small intes;ne drain fat and other nutrient- rich lymph into it via hepa;c portal system Gall Bladder Small pear-shaped organ on underside of liver Stores and concentrates bile during the fas;ng state When fat enters duodenum, mucosal cells release the pep;de hormone cholecystokinin on its release this s;mulates the gall bladder to contract and discharge bile Bile is alkaline and makes the food alkaline so pancrea;c enzymes can act on it Gallstones are usually cholesterol-based; may block the hepa;c or common bile ducts causing pain and jaundice Bile A watery greenish guid produced by liver and secreted via hepa;c duct and cys;c duct to gall bladder for storage Released on demand via common bile duct to an opening near the pancrea;c duct in duodenum Contains bile salts/acids, bile pigments (mainly bilirubin, the non-iron part of haemoglobin), cholesterol and phospholipids Bile salts and phospholipids emulsify fats, the rest Increase surface area to aid digestion are for excre;on accomplished by lapse and enzymes from pancreas Large amounts of bile (acids) secreted every day, but only rela;vely small quan;;es lost as 95% are reabsorbed in the ileum, returned to the liver and reused Pancreas Endocrine and exocrine gland The exocrine part produces many enzymes which enter the duodenum via the pancrea;c duct The endocrine part produces (insulin and glucagon) Secrete hormones directly into blood The exocrine pancreas has two main diges;ve func;ons: 1. Secretes diges)ve enzymes in response to cholecystokinin to help with diges;on of fats, starches, proteins 2. Secretes aqueous bicarbonate solu;on to help neutralise stomach acid entering small intes;ne  Contains digestive enzymes that pass to small intestine where they help to break down carbohydrates, proteins and lipids. Liquids secreted in pancreas and contains variety of enzymes Pancrea)c Fluid Acts on carbohydrates, proteins and fats Contains: Sodium bicarbonate to neutralise acidity of contents arriving from stomach (brings pH back up to 8) Pancrea)c amylase – carbohydrates → simple sugars (together with maltase, sucrase, lactase) Pancrea)c lipase – lipids → faky acids & glycerol Trypsin & chymotrypsin – protein → amino acids Nucleases – hydrolyse ingested nucleic acids (RNA/DNA) into component nucleo;des Func)ons of the liver including the role the liver plays in diges)on Heaviest organ 2 main lobes Filters blood Digestion Hkps://www.youtube.com/watch ?v=s2JwoqcnyS8 Time 5.39 minutes Major role it plays in digestion Peticites which produce bile Absorption and storage of vitamins A, D, E, K, B12 With pancreas it helps regulates blood glucose by storing glucose in the form of glycogen and releasing it as glucose when needed by body. Ques)ons Liver, gall bladder, bile, pancreas and pancreatic fluid Name the accessory organs of the diges;ve system CCK Chlolecystokin GI What hormone s;mulates the release of bile from the gall bladder? What is the func;on of the bile salts and phospholipids in the bile? The GI tract con)nued –the large intes)ne  Last part of GI tract Large Intes)ne (colon) Food not broken down any more Food enters mouth - bolus - enters oesophagus - leaves through oesophageal sphincter into stomach - leaves through pyloric sphincter into small intestine. Leaves small intestine at illeocecal valve - empties into large intestine. Absorp;on of remaining water Small intestine finish process of absorption of nutrients and digestion from indiges;ble food maker Residue passes into large intestine Further absorption of water and electrolytes not absorbed by small intestine take place Vitamins are synthesised Some electrolytes and indiges;ble Waste products are stored and eliminated food lee Stores and eliminates waste Absorbs vitamins produced by gut bacteria, especially vitamin K and certain B vitamins  Less muscular More goblet cells which secrete mucus for lubrica;on No villi Takes about 16 hours to complete remaining processes Gas – due to bacterial fermenta;on of undigested material Chyme mixed with mucus and bacteria (mostly commensals) → Faeces (given colour by bile pigments) Gut bacteria: - synthesise vitamins - digest polysaccharides for which we have no enzymes (10% of our calories) Rectum Last 13 cms of large intes;ne Stores solid waste un;l it leaves the body through the anus – external opening Peristal;c waves Sphincter relaxa;on (voluntary and involuntary) Ques)ons What is absorbed in the large intes;ne? Water and electrolytes not absorbed by small intestine What is the reason for gas produc;on in the large intes;ne? Bacterial fermentation of undigested material Diges)on  Process by which body break down food we eat into nutrients for energy, growth and cell repair Happens though the passage of food thought the GI tract Diges)on Involves the mixing of food, the movement of food and the chemical breakdown of larger food molecules into smaller ones(catabolism) Gut modiIes food physically and chemically and disposes of unusable waste ModiIca;on depends on exocrine and endocrine secre$ons and controlled movement of food through diges;ve tract Diges)ve juices Stomach and small intes;ne each produce a diges$ve juice Other diges;ve juices empty into the alimentary canal from salivary glands, gall bladder and pancreas Most juices contain diges$ve enzymes which speed up the reac;ons involved in the breakdown of food Diges)ve Enzymes AMYLASE: Salivary glands in pancreas 3 main starch → types: maltose → glucose LIPASE: PROTEASE: lipids → protein → faky acids amino Produced in pancreas and acids glycerol Produced by pancreas and stomach Diges)on of Carbohydrates Diges;on begins in the mouth (salivary amylase) Salivary and pancrea;c amylase converts disaccharides (double sugars) Intes;nal enzymes (sucrase, maltase, lactase) break down into disaccharides and monosaccharides Polysaccharide + salivary amylase -> maltose & small polysaccharides Undigested polysaccharides + pancrea;c amylase -> maltose, disaccharides + maltase, sucrase & lactase -> monosaccharides Diges)on of Proteins Starts in the stomach and ends in the small intes;ne Pepsin in stomach, trypsin and chymotrypsin in pancrea;c juice digest protein. Aminopep;dase present in intes;nal secre;on Inally digest protein into amino acids. Protein + pepsin -> short polypep;des Short polypep;des + trypsin, chymotrypsin -> small polypep;des & pep;des + carboxypep;dase, pep;dases, dipep;dases -> amino acids Diges)on of Lipids Bile produced by the liver is poured into the duodenum and brings about emulsiIca;on Pancrea;c lipase splits the lipid molecules into faky acids and glycerol Fats + bile salts -> emulsiIed fat droplets + pancrea;c lipase -> faky acids & glycerol Absorp)on Stomach absorbs only a few substances Include alcohol and aspirin Main absorp;on occurs in small intes;ne Occurs by combina;on of simple dijusion, facilitated dijusion and ac;ve transport Amino acids and glucose are directly transported to the liver via the hepa;c portal vein Absorp)on Majority occurs in the jejunum In small intestine Faky acids and glycerol are absorbed by intes;nal cells Iron absorbed in duodenum Vitamin B12 / bile salts absorbed in terminal ileum Water and lipids absorbed throughout By passive diffusioin Please complete the following table with the aid of Ross & Wilson P.342 Table 12.2 Summary of the sites of digestion and absorption of nutrients Small Intestine Nutrient Mouth Stomach Digestion Absorption Large Intestine Ques)ons Amylase What type of enzyme helps diges;on of starch? Proteases What type of enzyme helps digest protein? Lipase What type of enzyme helps digest lipids? Revision Exercise Review and revise the exercises on pages 366 & 367 in Waugh, A. and Grant, A. (2018) Ross & Wilson Anatomy And Physiology In Health And Illness. 13th ed. Elsevier. Links to youtube video hkps://www.youtube.com/watch/Og5xAdC8EUI TEDex diges