Compendium 3 Notes PDF

Compendium 3 Notes Lecture 1 Anatomy - Digestive tract also called alimentary tract is a continuous tube - Accessory organs primarily glands secrete fluids into the tract - Oral cavity (mouth) with salivary glands - Where food ingestion occurs - Pharynx (throat)...

Compendium 3 Notes Lecture 1 Anatomy - Digestive tract also called alimentary tract is a continuous tube - Accessory organs primarily glands secrete fluids into the tract - Oral cavity (mouth) with salivary glands - Where food ingestion occurs - Pharynx (throat) - Shared pathway for food and air - Oesophagus - Transports food to the stomch - Stomach - Where food is churned and mixed into chime - Small intestine (duodenum, ileum, jejunum) with liver, gall bladder and pancreas as accessory organs - Large intestine including cecum, colon, rectum and anal canal - Anus - The greater omentum connects the stomach to the large intestine - Mesentery proper - Connects the small intestines to the posterior body wall and provides a lot of blood supply Functions of the digestive system - Ingestion: introduction of food into the stomach normally via the mouth - Mastication: chewing (mechanical), chemical digestion requires large surface area o breaking down large particles mechanically facilitates chemical digestion - Secretive: lubricate, liquefy and digest e.g. mucous: secreted along the entire digestive tract, lubricates food, coats and protects lining - Digestion: mechanical and chemical digestion of food into nutrients - Making food usable by the body - Absorption: movement of nutrients out of the digestive tract into the blood stream - Elimination: waste products are removed from the body, faeces, defecation - The digestive system makes and releases Hormones, has a very important microbiome Histology of the digestive tract - One large tube from mouth to anus plus thr accessory organs 1. Mucosa: innermost layer which secretes mucous, touching the food or chime, epithelial avascular 2. Submucosa: connective tissue layer, contains blood vessels, nerves ect. 3. Muscularis: 2/3 muscle layers, movement and secretioncircular and longditudonal layers under involuntary control 4. Serosa/adventitia: outermost layer, connective tissue, stability holds everything in place, connects organs Peristalsis and segmentation - Process by which food moves through the gut waves of smooth muscle relaxation and contraction - A wave or a series of muscle relaxations or contractions, when relaxed the food can move forward and there will be a contraction behind it to push it forward Peritoneum - The walls and organs of the abdominal cavity are lined with serous membranes - Visceral peritoneum: covers organs - The parietal peritoneum: covers internal surface of the body wall - Mesentries: peritoneum (epithelial tissue) which connects organs together and small intestines to the back of the body wall - Double fold in the peritoneum - Routs by which vessels and nerves pass from body wall to organ - Greater omentum: connects stomach to the transverse colon - Lesser omentum: connect the stomach to liver and diaphragm Oral cavity - Digestion begins in the oral cavity - Hard pallet: hard bone anterior - Soft pallet: soft muscle posterior - Tongue - Muscular, important in chewing, swallowing and moving food around the mouth, taste buds - Teeth - Important for mechanical digestion - Masticate food and turn it into a bolus Teeth - Two sets of teeth - Primary: milk teeth, childhood - Lost from 5-10yrs old - Permanent or secondary: adult (32) - Types - Incisors (8) - Cutting - Canines (4) - Tearing - Premolars (8) - grinding - Molars (12) - Grinding Salivary glands - Salivary glands produce and secrete saliva into the oral cavity - Saliva protects the oral cavity, moistens, loosens and digests food - Amylase enzyme found in saliva that breaks down carbohydrates into smaller sugars - Lysozyme -- antibacterial enzyme involved in immune defence Pharynx and oesophagus - The pharynx connects the oral cavity to the oesophagus - Uvula (the soft pallet) prevents food and drink from entering the nasopharynx - Nasopharynx - The part behind the nose - Oropharynx - The part behind the oral cavity - Laryngopharynx - The part around the larynx - Oesophagus - The tube that connects the pharynx to the stomach 25cm long, lies posteriorly to the trachea , 25cm long - Epiglottis - Prevents food and drink from entering the trachea - Gastro-oesophageal sphincter Swallowing 1. Voluntary phase -- tongue pushes the bolus to the back of the oral cavity, towards the pharynx (oropharynx) 2. Pharyngeal phase -- soft pallet (uvula) closes off the nasopharynx. Bolus touches receptors on the oropharynx and the swallowing reflex moves the bolus down the pharynx and into the oesophagus. epiglottis covers trachea 3. Oesophageal phase -- bolus is moved down the oesophagus towards the stomach by peristalsis Stomach - Located in the abdomen - The holding point for food - Food comes from the oesophagus and the stomach mixes it (churns) into chyme (a thick liquid) - Produces mucus, hydrochloric acid, protein-digesting enzymes (pepsin) - Assists with the break down of food - Contains a thick mucus layer that contains and protects the epithelial cells on the stomach wall from acid pH 2-3 - Openings/sphincters - Gastroesophageal: to oesophagus - Pyloric: to duodenum - Parts - Cardiac (closest to the oesophagus) - Fundus (sits superiorly) - Body (main part) - Pyloric -- antrum and canal - Layers - Visceral peritoneum or serosa - Muscularis: 3 layers - Outer longitudinal - Middle circular - Inner oblique - Submucosa under the epithelial layer, connective (very rich in blood supply) - Mucosa -- simple columnar epithelium - Rugae -- folds in the stomach wall that allow the stomach to stretch after eating, increase the surface area, can hold up to 2L of contents Movements of the stomach - The 3 muscle layers enable the churning of food to make chyme - Combination of mixing waves (80%) and peristaltic waves (20% ) - Both oesophageal and pyloric sphincters are closed - Water takes about 1-2h to exit (via kidneys and urethra) after ingestion - Stomach empties every 4 hours (6-8 after a fatty meal and quicker with a spicy meal) Small intestine - 6 meters in length with a small diameter - Very folded to fit in the body - Large surface area for efficient absorption of nutrients - Connected to the posterior body wall by mesenteries - Divisions - Duodenum - First 25cm beyond the pyloric sphincter - Curves around the pancreas, chyme mixes with various digestive enzymes - Mucus from Brunner's glands (under the epoithelium) neutralises acidic chyme - Located in epigastric and umbilical regions - Jejunum - 2.5 meters long - A large amount of nutrient absorption - Extensive villi - Located in the left lumbar and umbilical region - Ileum - 3.5m long - End at the ileocecal junction - Located in the hypogastric region - Adaptions increase the surface area of the small intestine (600 fold) to increase absorption 1. Plicae circulars: circular folds in the wall of the small intestine 2. Villi: finger-like folds of epithelium, that contain capillaries and lacteals - The carbohydrates and proteins are absorbed into the blood and the lipids are absorbed into the lacteals 3. Microvilli: small extensions on epithelial cell surface Liver and gall bladder - The liver makes 100ml of bile per day - Bile enters the duodenum and helps to emulcify and break down large lipids into smaller lipids - The liver also filters the nutrient rich blood coming from the small intestines - The liver stores glucose as glycogen and can store lipids for energy - The liver detoxifies toxins and drugs - The gall bladder is a muscular sac which stores and concentrates bile - Bile enters the duodenum via the common bile duct and emulsifies fats/lipids Pancreas - Produces digestive enzymes - Produces insulin and glucagon for blood sugar homeostasis - The pancreas has an exocrine function meaning it makes a substance that exits the organ via a duct system - Lipase breaks down lipids - Pancreatic amylase breaks down carbohydrates - Trypsin breaks down proteins Large intestine - Once the chyme has reached the large intestine almost all of the nutrients have been absorbed from it - Absorption of water and NaCl (sodium chloride aka salt) - Extends from the ileocecal junction to the anus - Consists of the cecum, colon (ascending, transverse, descending and sigmoid), rectum and anal canal - Bacteria/microbes synthesise vitamins B and K - 18-24h transit time; chyme -\> faeces - 1500ml of chyme enters the cecum, 90% reabsorbed yielding 80-150ml of faeces - Defecation reflex triggered by rectal distension (rectum is dull of faeces) - Goblet cells secrete mucus allowing a smooth passage of faeces through the intestine and out through the anal canal Digestive process - Digestion: mouth, stomach and small intestine break food molecules for absorption into circulation, mechanical breaks down food particles into smaller ones and chemical breaks covalent bonds through digestive enzymes - Absorption : nutrients from the small intestine, water from the large intestine. Molecules are moved out of the digestive tract and into circulation for distribution throughout the body via the liver Lecture 2 Enzymes - A protein catalyst (made of proteins) that increases the rate at which a chemical reaction proceeds without the enzyme being permanently changed - Highly specific - active site on an enzyme can only bind to a specific reactant - Many different enzymes needed in the body for different chemical reactions - Often named by adding 'ASE' as a suffix to their reactant - Lipase is an enzyme that breaks down lipids - Protease is an enzyme that breaks down proteins Nutrients - Chemicals taken into the body to - Produce energy - Provide building blocks to build other molecules - 6 classes: - Carbohydrates -- mono/di/polysaccharides (sugars) -- plants and vegetables - Protein - chains of amino acids -- meat fish poultry beans legumes leafy green veg - Lipids - triglyceride -- oils, dairy, fats, eggs - Vitamins -- organic molecules -- vit A/B/E animal and plant products - Minerals -- inorganic nutrients -- calcium iron from animal and plant products - Water - Carbohydrates, proteins and lipids are the major organic macronutrients (organic = contains carbon) - We need a large amount of carbohydrates, protein, lipids and water - Only need small amounts of vitamins and minerals - Taken into the body without digestion - Essential nutrients are chemicals that must be taken into the body because we can't make them ourselves - Includes some amino acids, fatty acids, carbohydrates, water and most vitamins and minerals Recommended amounts - Raw foods tend to have the highest amounts of vitamins and minerals - Carbohydrates - 45-65% of daily kilocalories - Lipids - 20-35% or less of daily kilocalories - Proteins - 10-35% of total daily kilocalories Carbohydrates - Come from plants - Exception is lactose from milk - Contain carbon (C), Hydrogen (H), and Oxygen (O) = CHO - 2H and 1O for every C (the 2H:1O is the same for water) - Carbo = carbon, hydrate = hydrated/water - Large molecules are made up of small building blocks - Monosaccharides (mono = 1, saccharide = sugar) - Simple sugars are glucose and fructose Mono and disaccharides - Monosaccharides - Glucose (blood sugar) - Fructose (fruit sugar) - Galactose (milk sugar) - Disaccharides - Sucrose (table sugar) glucose + fructose - Lactose (milk sugar)- glucose + galactose - Maltose (two glucose) glucose + glucose Polysaccharides - Long chains (3000+ monosaccharides) - Glycogen - Animal polysaccharide - Glucose molecules - Stored in humans in liver and muscle until the body needs the energy - Starch and cellulose - Plant polysaccharides - Humans break down starch - Energy - Humans cant breakdown cellulose - Dietary fibre - Improves gastro intestinal health Carbohydrate absorption - Polysaccharide chain e.g. glycogen is digested by saliva (salivary amylase) in the oral cavity and by the pancreatic amylase in the duodenum - A disaccharide chain e.g. sucrose is digested by surcease in the intestine - Monosaccharide chain e.g. glucose is absorbed into the blood via the villi and microvilli in the intestine then the glucose is transported to the liver via the hepatic portal vein Uses of carbohydrates in the body - Glucose -\> ATP (energy) - Energy -\> warmth, movement, brain activity, muscle contraction, ect. - Excess glucose can be stored in the liver or muscles as glycogen - Excess beyond storage is turned into fat - Sugars also become part of DNA, RNA and ATP, glycoproteins and glycolipids Proteins - Contain carbon (c), hydrogen (H), oxygen (O), nitrogen (N), and sometimes sulphur (S) - From meat, nuts, eggs, dairy, legumes, green leafy veg - Amino acids are the basic building blocks - Each amino acid has an amine group (NH2), a carboxyl group (COOH), a hydrogen and a side group - A side group is what is different between amino acids - Amino acids link together to form peptides, poly peptides and proteins - Amino acids are not stored in the body - Essential amino acids cant be produced by the body so must be obtained through the diet e.g. histidine, isoleucine - Non essential amino acids are still required by our body but these we can synthesise from essential amino acids - Functions of proteins is to regulate body functions - Globular proteins (haemoglobin) - Structural -- muscle proteins or CT - Cell membrane transport - Enzyme - Antibodies - Hormones - Complete protein -- food that contains enough of all 9 essential amino acids - Meat, fish, poultry, milk, egg, cheese - Incomplete protein - Leafy green veg, beans, legumes, grains (have to mix these to get all essential amino acids) Protein absorption - Protein (long chain of amino acids)is digested by pepsin in the stomach - Polypeptides are digested by trypsin in duodenum - Peptides are broken down into individual amino acids are absorbed into the blood via villi and microvilli in the intestine Lipids - Composed mostly of carbon, hydrogen, oxygen and sometimes nitrogen and phosphorus - Lower ratio of O to C than in carbs, which makes them relatively insoluble in water - Lipids/fats ingested are broken down to release energy - Triglycerides make up 95% of fats in the body - Glycerol +3 fatty acids (building blocks of triglycerides) - Fatty acids - Different lengths (e.g. 14 or 18 C atoms) - Saturation -- how many H atoms are on each carbon on the chain - Saturated -- animal fats e.g milk butter chees beef and pork - Unsaturated -- plant sources - contains 1 or more double bonds in the carbon chain so there is less H atoms, more relaxed structure (liquid at room temp) - Trans fats -- unsaturated fats that are artificially altered and carry the highest CVS (cardiovascular system) risk - Increases risk of blocked ateries and high cholesterol - Used in a lot of fast foods - The more double bonds the helthier and less saturated something is Lipid absorption - Lipid (triglycerides) digestion begins in the duodenum - Bile from the gall bladder emulsifies lipids - Lipase from the pancreas causes further breakdown in the duodenum - Short-chain fatty acids (monoglycerides) are absorbed into the lymphatic system via lacteals in villi - Lipids are stored in the adipose tissue and liver until needed Uses of lipids in the body - Triglycerides: used as ATP (excess is stored in adipose or liver) - Cholesterol:found in liver and egg yolk or manufactured by body. Component of plasma membranes modified to form bile salts - Phospholipids: major components of plasma membranes, myelin sheath, part of bile - Eicosanoids: derived from fatty acids, involved in inflammation, blood clotting, tissue repair and smooth muscle contraction Water absorption - Approximately 9L of water enters the digestive tract each day - This includes secretions such as saliva (1L) gastric secretions (2L) bile (0.7L) pancreatic secretions (1.2L) small intestine secretions (2L) - 99% of water entering the digestive tract is absorbed - Water can move across the intestinal wall in either direction if required - Ions: sodium, potassium, calcium, magnesium and phosphate are actively transported in water Vitamins - Organic molecules (w/ carbon) in very small quantities in food - Essential for normal metabolism and can't be produced by the body - No one food provides all necessary vitamins, some are produced by intestinal bacteria e.g. vitamin K - Vitamins can be fat soluble (K, E, D, A) or water soluble (B + C) -- consider the route of admission and what you might need to have with them to make sure it is properly absorbed - Too much - Vitamin C -- stomach inflammation -- diarrhea - Vitamin A -- toxic during pregnancy (birth defects) - Vitamin D -- alters calcium metabolism - Vitamin deficiencies - Vitamin D -- rickets - Vitamin C -- Scurvy - Vitamin B (thiamine) -- beriberi Minerals - Inorganic nutrients (no carbon) - Major minerals \>100mg per day - Calcium, magnesium, sodium, potassium - Trace minerals \