Nutrition Metabolism and Digestion PDF

NUTRITION METABOLISM AND DIGESTION Food provides energy and nutrients that are essential for your health. NUTRIENTS: SUBSTANCES USED BY THE BODY TO PRODUCE ENERGY TO DRIVE PHYSIOLOGICAL PROCESSES AND PROVIDE BUILDING BLOCKS FOR GROWTH & REPAIR Classes. Carbohydrates, proteins, lipids, water: requ...

NUTRITION METABOLISM AND DIGESTION Food provides energy and nutrients that are essential for your health. NUTRIENTS: SUBSTANCES USED BY THE BODY TO PRODUCE ENERGY TO DRIVE PHYSIOLOGICAL PROCESSES AND PROVIDE BUILDING BLOCKS FOR GROWTH & REPAIR Classes. Carbohydrates, proteins, lipids, water: required in large amounts. Vitamins, and minerals: required in small amounts. Essential nutrients: (indispensable nutrients) must be ingested, and cannot be synthesized by the body (amino acids, fatty acids, most vitamins, water, minerals) NUTRITION: THE PROCESS BY THE BODY OBTAINS AND USES CERTAIN FOOD COMPONENTS. INCLUDES DIGESTION, ABSORPTION, TRANSPORTATION, AND CELL METABOLISM FOOD AND CALORIE BALANCE Your body uses energy to grow, move, be still, and sleep. The amount of energy you need depends on many factors including your age, your sex, your rate of growth, and your level of physical activity CALORIES-DRIVING ENERGY PROVISION FOR THE BODY The large molecules in food must be broken down to be absorbed into the blood and carried to cells throughout the body. THE PROCESS OF BREAKING DOWN FOOD INTO MOLECULES THE BODY CAN USE IS CALLED DIGESTION. Your cells then break the chemical bonds of the digested food particles and use the energy that is released to make ATP during the process of cellular respiration THE ENERGY AVAILABLE IN FOOD IS MEASURED BY A UNIT CALLED A CALORIE (FOOD LABELS.) The greater the number of calories in a quantity of food, the more energy that food contains. CARBOHYDRATES -> Most come from plants (exception: lactose from milk and dairy products) CARBOHYDRATES THAT EXIST AS SINGLE SUGAR MOLECULES ARE CALLED MONOSACCHARIDES OR SIMPLE CARBOHYDRATES (glucose, fructose, galactose). CARBOHYDRATES MADE OF TWO OR MORE SUGARS LINKED TOGETHER BY CHEMICAL BONDS ARE CALLED COMPLEX CARBOHYDRATES (disaccharides, polysaccharides) Complex carbohydrates must be digested (broken down) into simple sugars before cells can use their energy LACTOSE FROM DAIRY DAIRY PRODUCTS CONTAIN LACTOSE – GLUCOSE AND GALACTOSE LINKED TOGETHER (Lactose intolerance common) USE OF CARBOHYDRATES IN THE BODY - 2-3% total body mass - The main source of chemical energy for generating ATP (the only source used by the brain) - Carbohydrate metabolism is glucose metabolism (in digestion: polysaccharide -> GLUCOSE, fructose, and galactose-> GLUCOSE) - Excess glucose is converted to glycogen and stored in muscles and liver cells - Excess beyond storage is converted to fat RECOMMENDED CONSUMPTION OF CARBOHYDRATES 45-65% of total kilocalories Amounts of less than 100 g per day may result in the overuse of proteins for energy. Complex carbohydrates are recommended over simple sugars because they may contain vitamins & minerals and have less of an effect on blood sugar level PROTEINS 12-18% normal lean adults Proteins are chains of amino acids made up of large molecules with complex structure Types: Essential: must be obtained in the diet. Adults must get nine from food Nonessential: The body can synthesize Digestion: Complex protein structure broken down into Amino acids (20 types) Food Source for Essential: Most animal products such as eggs, milk, fish, poultry, and beef contain all the essential amino acids known as complete proteins. No single plant food contains all essential amino acids. Eating certain combinations of two or more plant products can. FUNCTIONS -> PROTECTION (antibodies), REGULATION (enzymes, hormones), STRUCTURE (collagen), MUSCLE CONTRACTION (action, myosin proteins filaments), TRASPORT ((Haemoglobin, Plasm membrane transporters and Ion Channel). RECOMMENDED CONSUMPTION OF PROTEINS-> 10-35% OF TOTAL KILOCALORIES - NITROGEN BALANCE  LIPIDS -> 18-25% body mass in lean individuals Insoluble in water, circulate in the blood as lipoproteins (form a complex with protein particles so they become more soluble) Functions in the body: Highly concentrated form of chemical energy (TWICE the energy per gram as carbohydrates or proteins).Triglycerides (95%): used for energy to produce A T P Remainder stored in adipose tissue or liver – this is LIMITLESS LIPIDS IN DIET-> Saturated fats and oils: single covalent bonds between carbons; found in meat fats, whole milk, cheese, and eggs. Unsaturated fats and oils: one or more double bonds between carbons. Monounsaturated fats have one double bond; found in olive and peanut oil. Polyunsaturated fats have two or more double bonds; found in fish and sunflower oil. Trans fats are processed polyunsaturated fats that raise L D L levels. Cholesterol: steroid found in liver, and egg yolks but not found in plants. Phospholipids: for example, lecithin; a major component of plasma membranes, found in egg yolk USE OF LIPIDS IN THE BODY : - Triglycerides: used to produce ATP - Excess stored in adipose tissue or liver - Cholesterol: can be eaten or manufactured in the body (a component of plasma membranes, that can be modified to form bile and steroids) - Phospholipids, lecithin part of the plasma membrane - Eicosanoids involved in blood clotting, tissue repair, and smooth muscle contraction - RECOMMENDED CONSUMPTION OF LIPIDS->A M D R is 20 to 35% for adults (ranges are high for children) Although lipids are essential nutrients, too much fat in the diet is known to harm several body systems. VITAMINS-> organic molecules that exist in minute quantities in food Essential vitamins must be obtained by diet. Classifications: - Fat-soluble: A, D, E, K. Can be stored in fatty tissues to the point of toxicity. - Water-soluble: B and C remain short time and then are excreted. Functions of vitamins function as coenzymes or parts of coenzymes (combine with enzymes and make the enzyme functional) MINERALS-> 4% of total body Inorganic nutrients necessary for normal metabolic functions. Obtained from animal and plant sources. Minerals attached to plant fibers are difficult to absorb. Daily requirements classified into Major minerals & Trace minerals FUNCTIONS-> Nerve function, Strength to bones and teeth, Buffers, Involved in osmotic balance (sodium), Components of coenzymes, vitamins, hemoglobin IRON->Component of hemoglobin;ATPproduction inelectron-transport system / DEFICIENCY SYSMPTONS-> Anemia,decreasedO2 transport,energyloss SODIUM->Osmotic pressure regulation; nerve and muscle function/ DEFICIENCY SYMPTOMS->Nausea, vomiting, exhaustion, dizziness  METABOLISM METABOLISM: TOTAL OF ALL CHEMICAL CHANGES THAT OCCUR IN THE BODY. CELLS ARE CHEMICAL FACTORIES THAT BREAK DOWN ORGANIC BIOMOLECULES (CARBOHYDRATES, PROTEINS, FATS) TO OBTAIN ATP ENERGY. ANABOLISM-> energy-requiring process where small molecules join to form a larger molecule CATABOLISM-> energy-releasing process where large molecules broken down into smaller ones. Energy from nutrient catabolism is used to produce A T P, which can then be used to drive the anabolic reaction ATP DERIVED FROM CATABOLIC REACTIONS DRIVES ANABOLIC REACTIONS 1. Catabolism of nutrients begins during digestion when large molecules, such as polysaccharides and fast, are broken down for absorption. The catabolism process continues in the cells when the absorbed nutrients are further broken down for ATP production. 2. The energy derived from catabolism drives anabolic reactions and processes such as active transport and muscle contraction. Anabolism occurs in all body cells as they divide to form new cells, maintain their intracellular structure, and produce molecules, such as hormones, neurotransmitters, and extracellular matrix molecules, for export. CHEMICAL REACTIONS IN METABOLISM-> occur when bonds break from between atoms, ions or molecules. CATABOLISM = BREAKDOWN OF ORGANIC MOLECULES –RELEASES ENERGY ANABOLISM = FORMATION OF NEW ORGANIC MOLECULES – USES ENERGY ENZYMES = PROTEINS THAT ACT AS CATALYSTS (SPEED UP CHEMICAL REACTIONS FUNCTION OF ATP-> Transfers energy from catabolic reactions that release energy to cellular activities that require energy Build up of muscle or bone Muscle contraction Cell division and growth Intracellular transport Cell membrane transport METABOLIC RATE-> IS MEASURED BY THE AMOUNT OF OXYGEN CONSUMED BY THE BODY/MIN. (affected by-> age, body size, outside ramps, muscle mass, movement, hormones) BASAL METABOLIC RATE (BMP)-> The oxygen consumption of an awake relaxed person 12-14 hours after eating and at a comfortable temp. DETERMINED BY-> AGE, GENDER, THYROID SECRETION REGULATION OF ENERGY METABOLISM: - CIRCULATING NUTRIENTS-> Molecules absorbed through the small intestine and brought to the cells -Glucose-Fatty acids-Amino acids) - ENERGY STORES-> Nutrients that are stored in the body can be used for energy GLUCOSE METABOLISM -> can be used to: produce ATP, store as glycogen, make new fatty acids, make several amino acids CATABOLISM OF GLUCOSE -> GENERATES ATP PRODUCTION 4 INTERCONNECTING STEPS, KNOWN AS AEROBIC RESPIRATION) 1 STEP: GLYCOLYSIS-> As soon as glucose enters the cell: the enzyme attaches a phosphate group which “traps” glucose inside the cell. Only liver cells have enzymes to remove phosphate again. Does not require oxygen: anaerobic reaction Glycolysis = Break down of glucose from a 6-carbon molecule into 2 three-carbon molecules called pyruvic acid. Requires a co-enzyme NAD (a Vit B)Produces only 2 net ATP overall and 2 electron carriers (NADH) If pyruvic acid builds up in the cytoplasm – it will be converted to lactic acid 2 STEP: FORMATION OF ACETYL COENZYME A -> Occurs in mitochondria Consumes oxygen =aerobic Each 3-carbon pyruvic acid molecule is converted to a 2-carbon acetyl molecule It also produces one NADH Carbon and oxygen atoms removed –released as CO 3 STEP: KREBS CYCLE REACTIONS-> aerobic requires oxygen, occurs in inner membrane mitochondria Acetyl CoA combines with 4 carbon molecules to form citric acid (6C) This is modified in the cycle to produce 2 ATP, releasing CO2 and reforming the 4C molecule Also: production of NADH and FADH2 4 STEP: THE ELECTRON TRANSPORT CHAIN (OXIDATIVE PHOSPHORYLATION)->aerobic requires oxygen produces the bulk of ATPs a series of enzymes on the inner mitochondrial membrane involved. Electron carriers pass their high-energy electrons through a series releasing energy in small steps to form ATP A process called oxidative phosphorylation- Forms 28 ATP molecules from 1 glucose molecule ANATOMY OF THE UPPER DIGESTIVE TRACT-> The alimentary canal or gastrointestinal (GI) tract digests and absorbs food Alimentary canal / GI tract–mouth–pharynx–esophagus–stomach–small intestine–large intestine Accessory digestive organs–teeth–tongue–salivary glands–liver–gallbladder–pancreas UPPER DIGESTIVE TRACT: ORAL CAVITY, ORAL FISSURE, OROPHARYNX, ESOPHAGUS ORAL CAVITY=MOUTH ANTERIORLY-> lips, fissure vestibule LATERALLY-> cheeks, buccinator muscle SUPERIORLY ->roof, hard and soft palate INFERIORLY -> tongue, Geniohyoid, mylohyoid and glossus muscles POSTERIORLY THE ORAL CAVITY IS CONTINUOUS WITH THE OROPHARYNX  HARD PALATE, formed by: - palatine processes of maxillary bones - horizontal plates of palatine bones - Raphe SOFT PALATE lies posterior to the hard palate - The posterior margin of the soft palate supports the uvula (U) - Closes off nasopharynx in swallowing - Muscular pharyngeal arches: - –Palatoglossal and palatopharyngeal - –Palatine tonsils (T) between arches on either side STRUCTURE OF THE TONGUE EXTRINSIC MUSCLES (x4) Change the position of the tongue, and move the tongue to maneuver food and swallowing INTRINSIC MUSCLES (X4) alter shape and size of tongue for speech and swallowing, tongue rolling All muscles innervated by the hypoglossal nerve (CN XII) TONGUE - BLOOD SUPPLY Arterial –lingual arteries (branch off the external carotid arteries) Venous–lingual veins (drain into the internal jugular veins) SALIVARY GLANDS-> 3 PAIRS:–Parotid –Submandibular –Sublingua - Produce saliva, a mix of serous and mucus fluid - Moisten mouth surfaces (mucous membranes) - Lubricate and dissolve food in chewing/mastication–mechanical breakdown - Begin chemical breakdown of food PAROID GLAND-> Inferior to the zygomatic arch, covers the lateral and posterior aspect of the mandible - Produce watery serous secretion only–enzyme salivary amylase (breaks down starches) - Drained by a parotid duct, surrounded by a parotid capsule - Facial Nerve located within the gland - Mumps Parotid Duct -pierces the cheek muscle and opens in the oral cavity opposite the 2nd upper molar tooth (involved in mastication) SUBMANDIBULAR GLANDS ->Medial to the inferior margin of the mandible, anterior to the angle  - Mucus AND serous secretions - The greatest volume of saliva production - Submandibular ducts–open immediately posterior to teeth–either side of the lingual frenulum SUBLINGUAL GLANDS->Covered by the mucous membrane of floor of the mouth - Produce mucous secretion:–buffer and lubricant - Sublingual ducts (8-20 ducts)–either side of the lingual frenulum TEETH, made of: –enamel -covers the crown –dentine -hard avascular calcified tissue types of teeth: Incisors Canines Bicuspids/premolars Molars Deciduous teeth: -primary teeth -2,1,0,2 Secondary teeth -permanent dentition -2,1,2,3 per quadrant MUSCLES OF MASTICATION->Temporalis, Masseter, Lateral pterygoid, Medial pterygoid PHARYNX (nasopharynx, oropharynx, laryngopharynx) A funnel-shaped tube that extends from the back of the nasal cavity to the esophagus posteriorly, and to the larynx anteriorly –Nasopharynx functions in respiration only –Both oropharynx and laryngopharynx share digestive and respiratory functions –Skeletal muscle contractions help propel food to esophagus during deglutition (swallowing) OESOPHAGUS-> Collapsible, smooth muscle tube that connects the pharynx to the stomach for transport Lined with non-keratinized stratified squamous epithelium–Multi-layers of moist cells abraded during swallowing - 3 PARTS-> CERVICAL (NECK, C6-T1), THORACIC (CHEST, OPENING IN DIAPHRAGM, T10), ABDOMINAL (T11) Superior oesophageal sphincter(cervical part) –regulates the movement of food from the pharynx into the esophagus Inferior oesophageal sphincter(abdominal part) –regulates the movement of food from the esophagus to the stomach, and prevents regurgitation of acidic stomach contents (heartburn) TONGUE TIE-> The Lingual frenulum tethers the bottom of the tongue to the floor of the mouth, Restrictive movement of the tongue LIVER-> largest gland in the body (1500 grams, 2% body weight Located-> right hypochondrium, inferior to diaphragm  Features 2 Surfaces: - The diaphragmatic surface is divided into anterior, right (lateral), superior, and posterior, covered with visceral peritoneum - Visceral surface -inferior part of the liver, opposes visceral organs of GIT HAS 4 LOBES: RIGHT, LEFT, CAUDATE, AND QUADRATE THE FALCIFORM LIGAMENT: - Separates the right and left lobes anteriorly - Suspends the liver from the diaphragm and anterior abdominal wall VISCERAL SURFACE-> H-shaped structure, crossbar porta hepatis The quadrate lobe lies between the gallbladder and the falciform ligament The caudate lobe lies between the IVC and the ligamentum venosum The lesser omentum anchors the liver to the lesser curvature of the stomach The hepatic blood vessels enter the liver at the porta hepatitis The gallbladder rests in a recess on the inferior surface of the right lob PORTA HEPATIS (located on the visceral surface)-> entrance/exit for the liver -common hepatic artery-Oxygen-rich blood -portal vein-Oxygen-poor, nutrient-rich -hepatic ducts BLOOD SUPPLY-> Hepatic artery 25% / Portal vein 75% Venous drainage from the liver hepatic veins into the inferior vena cava PORTAL VENOUS SYSTEM All blood from the GIT enters the liver via the portal vein Portal vein = splenic, superior, and inferior mesenteric vein From the liver blood enters the IVC via the hepatic veins LIVER ANATOMY-> Hexagonal-shaped liver lobules are the structural and functional units of the liver –Composed of hepatocyte (liver cell) plates radiating outward from a central vein –Portal triads are found at each of the six corners of each liver lobule  Portal triads consist of bile canaliculi and–Hepatic artery –supplies oxygen-rich blood to the liver–Hepatic portal vein –carries venous blood with nutrients from digestive viscera HEPATOCYTES’ FUNCTIONS INCLUDE: - Production of bile - –Processing blood-borne nutrients - –Storage of fat-soluble vitamins - –Detoxification Secreted bile flows between hepatocytes toward the bile ducts in the portal triads GALLBLADDER (PEAR SHAPED, 7-10CM LONG, 50ML STORAGE CAPACITY) The digestive function of the liver is to produce bile Storage organ for bile Intraperitoneal structure Lies against the visceral surface of the liver in the gallbladder fossa ANATOMICAL AREAS : Fundus -projects from the inferior border of the liver Body -contacts the visceral surface of the liver Neck –narrow portion, tapers of to become the cystic duct (spiral valve) Cystic duct –connects the neck of the gallbladder to the common hepatic duct Bile leaves the liver via: The right and left hepatic ducts Hepatic ducts, which fuse into the common hepatic duct The common hepatic duct, which fuses with the cystic duct These two ducts form the bile duct BILIARY TREE The bile ducts descend posteriorly to the 1stpart of the duodenum At the 2ndpart of the duodenum the bile duct comes into contact with the pancreatic duct  Unite to form the hepatopancreatic ampulla The distal end of the ampulla opens into the duodenum through the major duodenal papillae Contraction of the sphincter of Oddi prevents bile from entering the duodenum Bile thus passes back up through the cystic duct into the gallbladder for concentration and storage BLOOD SUPPLY Cystic artery coming from the right hepatic artery (coeliac trunk) Cystic veins drain into the portal vein PANCREAS Accessory digestive organ Both retro & intra peritoneal structure Both endocrine & exocrine functions Posterior to the stomach Laterally -spleen Medially -duodenum–The duodenum encircles the head and the tail connects to the spleen Head–the widest part; lies within the C-shaped curve created by the duodenum Uncinate process–a projection arising from the lower part of the head; that lies posterior to the superior mesenteric vessels. Neck–located between the head and the body of the pancreas. It overlies the superior mesenteric vessels Body–centrally located, lies behind the stomach Tail–left end that lies within close proximity to the hilum of the spleen; is contained within the splenorenal ligament with the splenic vessels; only part of the pancreas that is intraperitoneal PANCREAS BLOOD SUPPLY Superior pancreaticoduodenal artery (coeliac trunk) Inferior pancreaticoduodenal artery (SMA) Nervous supply -ANS DUCT SYSTEM The pancreatic duct runs the length of the pancreas and unites with the common bile duct Forms the hepatopancreatic ampulla of Vater Opens into the duodenum via the major duodenal papilla Secretions into the duodenum are controlled by a muscular valve –the sphincter of Oddi, which surrounds the ampulla of Vater, acting as a valve The exocrine pancreas secretes pancreatic juice which breaks down all categories of foodstuff (Pancreatic amylase) THE ENDOCRINE FUNCTION OF THE PANCREAS IS TO RELEASE INSULIN AND GLUCAGON LIVER-> The largest organ receives 25% of cardiac output, and a greater variety of functions than any other organ, due to: diverse enzymes, unique structure, and receives venous blood from the intestine. LIVER LOBULE-> contact between the HEPATOCYTES (LIVER CELL) AND THE CONTENT BLOOD LIVER LOBULES-> Cells are arranged into functional units called liver lobules. In the middle of each lobule is a central vein. All the central veins converge to form the hepatic vein which drains into the vena cava At the periphery of each lobule is a hepatic portal vein and a hepatic artery. Blood mixes in sinusoids: - Uptake of oxygen, nutrients, and toxins by cells –Substances returned to blood –Bile made by liver cells put into bile canaliculi –Blood drains via the central vein, to the hepatic vein and inferior vena cava BLOOD SUPPLY OF LIVER Arterial blood: Hepatic artery – supplies oxygen-rich blood to the liver Venous Blood: 70% of blood from the intestine and spleen goes to the liver via the portal venous system. This contains high levels of nutrients THE LIVER, PANCREAS, AND GALLBLADDER ALL CONNECT TO THE GASTROINTESTINAL TRACT VIA: THE DUODENUM LIVER HAS A CENTRAL ROLE IN BODY TEMPERATURE REGULATION-> PRODUCES HEAT, the main heat-producing organ of the body and distributes it around the body- contributes to maintaining normal body temperature - DETOXIFICATION OF BLOOD-> The Liver can inactivate and remove hormones, drugs, toxins, and other biologically active molecules from the blood by - Metabolizing products making them less potent (first-pass metabolism)- drugs & alcohol. - Making products water-soluble (conjugation with a protein) so they can be excreted into the bile or urine- for example, bilirubin - Phagocytosis of any bacteria or foreign agents by Kupffer cells (resident white blood cells) - Chemical alteration of the molecules. - Ammonia (toxic) is produced by removing nitrogen from amino acids. - The liver converts it into urea (relatively harmless) which is excreted in large amounts in urine LIVER STORAGE FUNCTIONS: 1. Stores glycogen –carbohydrates broken into glucose and stored as glycogen) 2. Stores iron (ferritin) and copper 3. Stores fat soluble vitamins A, D,E, and K as well as synthesis the water-soluble Vit B12 and folate Released into the body when needed BILE PRODUCTION IN THE LIVER LOBULES ( BILE AND BLOOD DO NOT MIX IN THE LIVER) The hepatocytes produce bile. It is then secreted into bile canaliculi Drains into bile ductule and hepatic ducts. Stored in gallbladder BLOOD FLOWS WITHIN SINUSOIDS FROM A PORTAL VEIN TO A CENTRAL VEIN BILE FLOWS WITHIN HEPATIC PLATES FROM THE CENTER TO BILE DUCTALS AT THE PERIPHERY BILE PRODUCTION The liver cells produce and secrete 250 – 1500ml of bile/day. Bile is a watery, yellowish-brown or olive-green substance Bile salts emulsify lipids facilitating fat digestion Bile salts: produced in the liver and derived from cholesterol. Bilirubin: a product of iron of worn-out RBCs broken down in the spleen. It travels to liver and is conjugated (with glucuronic acid) in the liver which renders it soluble for excretion into bile. Bile enters the small intestine - contents excreted in faeces Small amount reabsorbed across the intestinal wall into the bloodstream - excreted in kidneys GALLBLADDER AND BILE Bile is stored and concentrated (x10) in the gallbladder until it is needed When required hormones (CCK and secretin) from the small intestine cause the gallbladder to contract and eject bile into the duodenum CLINICAL APPLICATION: If obstruction of the biliary tree occurs a series of symptoms develop Decrease of bile salts in the intestine leads to: decreased absorption of fat into lymphatics increased fat in feces = steatorrhoea Faeces become pale in color Bilirubin in mucous membranes – yellowish tinge to the skin THE LIVER IS RESPONSIBLE FOR THE METABOLISM OF CARBOHYDRATES FATS AND PROTEINS The Small Intestine connects to the Liver via the Hepatic Portal Vein Metabolic Functions of the Liver The hepatocytes extract nutrients and other substances from arterial and portal blood and carry out a large number of biochemical reactions. Some of the products are used by the liver but some are transported and used in other parts of the body. Carbohydrate, protein, and lipid metabolism LIPID METABOLISM Hepatocytes take up chylomicrons (lipids) and synthesize them into various lipids required by the body. Examples:  Lipoproteins: transport fatty acids around the body. Cholesterol : to make bile salts. Phospholipids : cell membrane structure CHOLESTEROL & LIPOPROTEINS 15% Cholesterol ingested; 85% made in liverTransported using lipoproteins. LDL Cholesterol 60%. Transports cholesterol to cells. Cells have LDL receptors, allowing cells to take in cholesterol and other lipids. # of LDL receptors become less once the cell’s lipid/cholesterol needs are met. Excess cholesterol can be deposited in arterial walls. The BAD guy HDL Cholesterol 30% Transports excess cholesterol from cells to the liver. The GOOD guy Eating food rich in saturated fats increases LDL and decreases LDL receptors PROTEIN METABOLISM Hepatocytes take up amino acids and synthesises them into various forms of proteins that are required by the body. Plasma Protein Synthesis –Albumin constitutes 70% of the total plasma protein. Contributes most to the colloid osmotic pressure in the blood. –Synthesises clotting factors. –Globulins: plasma transport proteins for cholesterol and some hormones. Amino acids–used as building blocks for cellular structure and function CARBOHYDRATE METABOLISM Crucial role in maintaining blood glucose levels within normal limits (3.5-7mmol/L). Post meal, blood rich in glucose enters the liver via the portal vein. Hepatocytes prevent the blood glucose level from rising too high by absorbing some glucose and converting it to glycogen(25% of body glycogen stores are in the liver) Also converts excess glucose to triglycerides (stimulated by INSULIN) which is then stored in adipose tissue LIVER: Role In Fasting (Glycogenolysis) During fasting, the liver prevents the blood sugar level from dropping by releasing glucose from glycogen stores into the bloodstream (stimulated by the hormone GLUCAGON) Also converts amino acids and triglycerides into ketones (alternative energy source) STOMACH Dilated part of the digestive tract Stores food T7and L3 J-shaped Size/capacity: variable Located in the Epigastric region Relations: Anterior: anterior abdominal wall, liver, diaphragm Posterior: ‘stomach bed 2 openings: cardiac and pyloric 2 surfaces: anterior and posterior surfaces 2 borders: lesser and greater curvatures-short lesser curvature forms medial surface-long greater curvature forms lateral surface Intraperitoneal Greater and lesser omenta attached STOMACH REGIONS Cardia surrounds the superior opening of the stomach Fundus-the rounded, often gas-filled portion superior to and left of the cardia Body-the large central portion inferior to the fundus Pyloric part(antrum + canal) -area connects the stomach to the duodenum OMENTUM-> ORGAN Lesser omentum –attached to the lesser curvature of the stomach Greater omentum –attached to the great curvature of the stomach, fatty sheet, hangs like an apron PYLORIC SPHINCTER Located between the pylorus and the duodenum Controls the exit of chyme(food and gastric acid mixture) from the stomach Increasing intragastric pressure causes the stomach to overcome the pylorus and empty GERD -Gastroesophageal reflux disease STOMACH BLOOD SUPPLY Coeliac artery + branches: left gastric, splenic, common hepatic Venous drainage: gastric, gastro-omental, splenic STOMACH INNERVATION Autonomic nerves Parasympathetic = vagus (CNX) Sympathetic = thoracic splanchnic nerves SMALL INTESTINE 3 parts -Duodenum, Jejunum, Ileum Plays a key role in the digestion and absorption of nutrients 90% of nutrient absorption occurs in the small intestine Runs from the pyloric sphincter of the stomach to the ileocecal valve DUODENUM First part of the small intestine, connects stomach to jejunum, shortest part of small intestine, C-shaped 4 parts –superior, descending, inferior, ascending Half of superior part has mesentery (duodenal cap), remainder retroperitoneal Blood Supply –Coeliac artery (1st& 2nd) -superior pancreaticoduodenal artery –SMA (3rd& 4th) -inferior pancreaticoduodenal artery Veins -drain into the portal vein Innervation-autonomicsympathetic: local plexi parasympathetic: vagus JEJUNUM Second part of the small intestine Runs from duodenum to ileum Length -40% of 7 meters (20 feet) Locations -central abdomen, umbilical + left lumbar regions Blood Supply: –Superior Mesenteric vessels -Jejunal and Ileal Arteries –Jejunal veins drain into the portal vein  Innervation-autonomicsympathetic: local plexus parasympathetic: vagus ILEUM Third & longest part of the small intestine, from the jejunum to termination (ileocaecal junction), intraperitoneal Length-60% of 7 metres (20 feet) Location -lower right quadrant Peritoneal attachment to the posterior abdominal wall is called the mesentery, fan-shaped blood Supply Superior Mesenteric vessels -ileal & ileocolic branches Ileal veins drain into the portal vein Innervation autonomic sympathetic: superior mesenteric plexus parasympathetic: vagus THE MESENTERY ->is a double fold of peritoneal tissue that suspends the small intestine and large intestine from the posterior abdominal wall. JEJUNUM AND ILEUM ->are suspended by a peritoneal fold called the mesentery The mesentery attaches the Jejunum and Ileum to the posterior abdominal wall. The mesentery is fan shaped, containing the bloods vessels supplying the Jejunum and Ileum. Root of the mesentery -15 cm long -Runs across from the left side of L2 to right iliac fossa: downwards obliquely to the right -Crosses abdominal aorta, inferior vena cava, and right ureter HIATUS HERNIA Occurs when a part of the stomach protrudes into the chest through the oesophageal hiatus in the diaphragm. There are two main types of hiatal hernias:–Sliding–Rolling GLUCOSE IS SOURCED FROM CARBOHYDRATES (most come from plants except-> lactose) Carbohydrates that exist as single sugar molecules are called monosaccharides or simple carbohydrates glucose, fructose, galactose 2-3% total body mass Main source of chemical energy for generating ATP Only source used by the brain Carbohydrate metabolism is glucose metabolism DIGESTION &ABSORPTION OF CARBOHYDRATES-> begins in the mouth, salivary amylase, nothing in the stomach, continues in small intestine using pancreatic amylase and brush border enzyme  Can be absorbed across epithelial cells of mucosa as a single monosaccharide (glucose) Diffuse into the bloodstream- into the hepatic portal system Under normal conditions, one-third of the glucose in the portal vein is taken up by the liver, and the rest of it is delivered to the rest of the body through arterial blood GLUCOSE IN THE BLOOD CIRCULATES AND IS TAKEN UP BY THE CELL Insulin-dependent except for the brain GLUCOSE ENTERS THE METABOLIC PATHWAY AND GENERATES ATP 1 GLUCOSE = 32 ATP BLOOD GLUCOSE REGULATION (GLAND AND HORMONE) Excess glucose converted to glycogen and stored in muscles and liver cells OR CONVERTED TO FAT Carbohydrate metabolism Crucial role in maintaining blood glucose levels within normal limits (3.5-7mmol/L). Post-meal, blood-rich glucose enters the liver via the portal vein. Hepatocytes prevent the blood glucose level from rising too high by absorbing some glucose and converting it to glycogen(25% of body glycogen stores are in the liver) Also converts excess glucose to triglycerides (stimulated by INSULIN) which is then stored in adipose tissue During FASTING, the liver prevents the blood sugar level from dropping by releasing GLUCOSE from GLYCOGEN stores into the bloodstream (stimulated by the hormone GLUCAGON) Also converts amino acids and triglycerides into ketones (alternative energy source) BLOOD GLUCOSE MONITORING-> continuous monitoring and traditional glucose testing In the early morning hours, hormones, including cortisol and growth hormone, signal the liver to boost the production of glucose, which provides energy that helps you wake up. This triggers beta cells in the pancreas to release insulin to keep blood glucose levels in check. Note: Acute/chronic stress elevates blood glucose – liver release energy in glucose