APL6 Digestive System PDF

Year 1 Dental Hygiene & Therapy DE7102: Biomedical Sciences Anatomy & Physiology The Digestive System School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Lecture-specific Learning Outcomes...

Year 1 Dental Hygiene & Therapy DE7102: Biomedical Sciences Anatomy & Physiology The Digestive System School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Lecture-specific Learning Outcomes Identify the structures that comprise the alimentary canal Identify the structures which comprise the accessory organs associated with the alimentary canal State the activities of the alimentary canal Explain the process of mastication and deglutition Explain the process of chemical digestion within the alimentary canal Describe the functions of the large intestine Describe the function of the accessory organs associated with the alimentary canal School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Glossary INGESTION = Taking food into the alimentary canal DIGESTION= Mechanical breakdown of food by mastication, Chemical breakdown of food by enzymes ABSORPTION = Digested food substances pass through walls of some organs of the alimentary canal into blood and lymph for circulation around the body ELIMINATION = Substances which cannot be digested/absorbed are excreted by the bowel as faeces DEFAECATION = elimination of faeces from the body MASTICATION = the act of chewing DEGLUTATION = the act of swallowing PERISTALSIS = Rhythmical muscular contractions that propel foodstuffs and waste products along the intestines of the alimentary canal School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Digestion The chemical breakdown of complex biological molecules into their component parts Lipids to fatty acids Proteins to individual amino acids Carbohydrates into simple sugars Produces various chemicals to break down the food Filters out harmful substances Gets rid of solid wastes School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Digestion Mechanical, changes the physical form of food: Chew Tear Grind Mash Mix School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Digestion Chemical, changes the chemical composition of food with the aid of digestive enzymes Digestive enzymes are special proteins that help break up large molecules of food into very tiny molecules that can be absorbed and used by the cells in the form of nutrition. School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Phases of Digestion Ingestion Movement Digestion Absorption Further digestion School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University The Digestive Tract (Alimentary canal) A long muscular tube with many sections and areas Begins with the mouth and ends with the anus 1. Mouth 2. Oesophagus 3. Small intestine 4. Large intestine 5. Rectum and anal canal School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  The Digestive Tract Parts of the Digestive Tract – Mouth – Pharynx – Esophagus – Stomach – Small Intestine – Large Intestine School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Accessory Parts Organs that are not in the digestive tract but helps in the digestion Teeth - DONE Tongue - DONE Salivary glands - LAST TIME Liver - TODAY Gall bladder - TODAY Pancreas - TODAY School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Mouth Functions: Food enters in the mouth or oral cavity Tasting Mechanical breakdown of food Secretion of salivary glands (salivary amylase) Structures in the mouth that aids digestion: Teeth – cut, tear, crush and grind food Salivary glands – produce and secrete saliva into the oral cavity Saliva moistens the food and contains enzymes (ptyalin or salivary amylase) that begins digestion of starch into smaller polysaccharides School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Mouth Tongue Mixes and rolls food into tiny mashed up bits (Bolus) Pushes the bolus toward the pharynx and into the oesophagus when swallowing School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University Human Deciduous and Permanent Teeth School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University Mechanism of Swallowing Swallowing is a coordinated activity of the tongue, soft palate, pharynx and esophagus. Phases Food is pushed into the pharynx by the tongue. (voluntary) Tongue blocks the mouth Soft palate closes off the nose Larynx (Adam’s Apple) rises so the Epiglottis (a flap of tissue) can close the opening of the trachea. School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University Mastication and Deglutination Saliva moistens food Bolus formed Voluntary muscles of tongue and cheeks push bolus backwards into pharynx Muscle of pharynx propel bolus into oesophagus and then into stomach Presence of bolus in pharynx stimulates peristalsis All other routes are closed to bolus Soft palate rises up and occludes nasal part of pharynx School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Oesophagus A straight muscular tube which connects the mouth with the stomach Food takes about 4 to 8 seconds as it passes through to the stomach Its walls contain smooth muscles that contracts in wavy motion (Peristalsis) Peristalsis propels food and liquid slowly down the esophagus into the stomach Cardiac sphincter (ring-like valve) relaxes to allow food into the stomach School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Peristalsis School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Stomach J-shaped muscular sac Has inner folds (rugae) that increases the surface area of the stomach Churns and grinds together the bolus into smaller pieces Food is mixed with gastric juices (hydrochloric acid (HCL) and enzymes) secreted by the stomach walls HCL helps break down food and kills bacteria that came along with the food School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Stomach School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Gastric Juice Pepsinogen Water which helps to Activated into pepsin by hydrochloric liquefy food acid Pepsin begins digestion of proteins Hydrochloric acid Breaks proteins into smaller Acidifies food molecules Stops action of salivary Intrinsic factor amylase Necessary for absorption of Vit B12 Kills microbes Mucus Prevents injury to stomach wall by Provides acid environment lubricating contents for effective digestion by Converts the bolus into a liquid (chyme) after 4 hrs of mechanical and pepsin chemical digestion School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Movements in Stomach School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Small Intestine Long (20 ft.), coiled tube beneath the stomach Has three parts: Duodenum upper part connected to the stomach where the digestive juices from the pancreas and the liver combine with chyme making it thin and watery Jejunum Ileum School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Small Intestine Site of greatest amount of digestion and absorption School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Small Intestine Takes about 4 – 8 hrs to complete its journey Mucosa (inner wall) – secretes several enzymes that acts on the food Where the pancreatic enzymes are emptied into Digested nutrients are absorbed through intestinal walls Absorbed materials cross the mucosa into the blood then other parts of the body for storage or further chemical change School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Small Intestine Has folded inner walls covered with fingerlike projections (villi; sing. = villus) Each villus has tinier projections called microvilli that absorbs digested food Villi and microvilli increases the surface area of the small intestine for greater absorption Peristalsis moves the undigested food to the large intestine School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Movement in small intestine: Mixing: Segmental contraction that occurs in small intestine Secretion: Lubricate, liquefy, digest Digestion: Mechanical and chemical Absorption: Movement from tract into circulation or lymph Elimination: Waste products removed from body School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Large Intestine a.k.a. Colon larger diameter, but shorter (5 ft.) Water is absorbed from the undigested food making the waste harder until it becomes solid Waste stays for 10–12h School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Large Intestine Waste is pushed into the expanded portion (rectum) of the large intestine Solid waste stays in the rectum until it is excreted through the anus as faeces Appendix hangs on the right side of the large intestine School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Large Intestine Functions 1. Absorption of water continues until a semi-solid consistency of faeces is achieved Mineral salts and some drugs are also absorbed into blood capillaries in the large intestine 2. Microbial activity – microbes synthesize Vit K and folic acid 3. Defaecation – elimination of faeces from the body School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Accessory Organs - Liver Produce or store enzymes that helps in digestion Largest gland of the body (skin?) Stores vitamins A,D,E,K Stores sugar and glycogen Produces bile (watery, greenish substance) Secretes bile to the gall bladder via the hepatic duct and cystic duct Converts glucose into glycogen in the presence of insulin Changes liver glycogen to glucose in the presence of glucagon Desaturates fats – converts stored fat into a form easily utilised by the tissues to provide energy Forms plasma proteins and most blood clotting factors from available amino acids Metabolizes ethanol from alcohol Inactivates hormones – cortisol, insulin, glucagon, sex hormones, thyroid hormones and aldosterone School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University Accessory Organs – Gall Bladder Stores bile in between meals Secretes bile to the duodenum through the bile duct during mealtime Bile contains bile salts, pigments, cholesterol and phospholipids Bile is an emulsifier NOT an enzyme Emulsifier – dissolves fat into the watery contents of the intestine School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University Accessory Organs – Pancreas Produces a juice that contains enzymes (amylase and insulin) to break down carbohydrates, fats and protein Secretes the juice into the duodenum through the pancreatic duct Approximately 12-15cm long Head lies in curve of duodenum Tail lies in front of left kidney Body lies behind stomach Just before entering duodenum pancreatic duct joins common bile duct to form ampulla of bile duct Islets of Langerhans – see endocrine system School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Pancreatic Juice Water Mineral salts Enzymes Pancreatic amylase – splits starch and dextrin into maltose Lipase – splits fats into fatty acids and glycerol Peptidase precursors (trypsinogen/chymotrypsinogen) – splits proteins School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  The Excretory System Gets rid of wastes and other substances that the body doesn’t need 1. Solid Waste – from the Digestive System in the form of faeces 2. Metabolic Wastes – produced by chemical reactions like respiration, hydrolysis, synthesis and neutralization Water Carbon Dioxide Salts Urea School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Removal of Wastes Egestion = removal of digestive waste Excretion = removal of metabolic waste School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Organs of Excretion - Skin Allows water, salt and urea to diffuse from the blood (capillaries) into the sweat glands Releases sweat from the sweat glands through the sweat ducts out to the skin pores School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University Organs of Excretion - Lungs Excretes the waste product of respiration during exhalation Carbon dioxide and water vapor School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University  Organs of Excretion- Liver Part of the digestive, circulatory and excretory systems Removes excess amino acids from the body Breaks down the amino acids through deamination to form the urea which is excreted in the urine School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University Organs of Excretion – Kidneys (See excretory system) Major excretory organs of the body which removes most of the body wastes Purify blood by filtering out water, salts, digested food particles and urea in the form of urine Urine passes out through the urinary tract – Ureter – a tube that transports urine to the urinary bladder – Urinary Bladder – a sac of tissue that has the ability to expand as it fills with urine – Urethra – a tube at the bottom of the bladder where urine passes out of the body School of Dentistry Yr Ysgol Ddeintyddiaeth © School of Dentistry, Cardiff University