Unit ix
- 1. 1 Year 1 Semester 2 UNIT IX Life saving son Post Rn BScN NIAMAT ULLAH
- 2. unit ix metabolism of carbohydrates, FATS, PROTIEN There are four (4) stages of food processing: Ingestion (eating): taking in nutrients (important part in food) Digestion: using physical and chemical means to break down Complex organic molecules into smaller usable parts Absorption: pulling in digested molecules into the cells of the digestive tract, then into the blood Egestion: the removal of waste food materials (e.g. cellulose = fiber) from the body. These four steps are done by the digestive system. The steps occur in the gastrointestinal tract (a long tube open at both ends). Accessory glands Such as the liver and pancreas help during the process. The GI tract is also called the Alimentary tract. 1. Ingestion: The mouth food enters the gastrointestinal tract through the mouth. 2. Digestion: A) Mouth – both physical (mechanical) and chemical digestion begins here Physical - Two main structures involved: teeth and tongue i) TEETH - four types (normal adult has 32 teeth on average). Tooth type Number Function a) Incisors 8 cut food b) Canine 4 pierce and tear food c) Bicuspids 8 pierce and tear
- 3. d) Molars 12 crush and grind ii) Tongue - both tongue and teeth help to physically break apart food. Chemical digestion: using enzymes to break up food In the mouth, Salivary glands produce Saliva which contains the enzyme amylase which acts on starch, breaking it into maltose. STARCH amylase maltose Bolus: the resulting ball of food in the mouth made by the actions of the teeth, tongue, and saliva. PERISTALSIS: the rhythmic muscular contractions that push digested food in one direction through the gastrointestinal tract. The bolus is swallowed and travels down the esophagus into the stomach. It moves down the esophagus by peristalsis. B. STOMACH: physical and chemical digestion the bolus passes through the Cardiac Sphincter, the top opening in the stomach. Sphincter: a muscle that controls the opening i) Cardiac: esophagus & stomach ii) Pyloric: stomach and duodenum Physical: the stomach is a muscular storage organ that churns the food Chemical: Gastric juice mixes with bolus- stomach contents now called Chyme (Gastric juice contains: a) HCl – hydrochloric acid b) Pepsin – enzyme that breaks down protein HCl: - helps breakdown fibrous tissue - kills bacteria- helps pepsin work properly (ph = 2 optimal pH for pepsin). PEPSIN: - enzyme begins to break down PROTEIN into smaller polypeptides. MUCUS: - also made by stomach to protect itself from strong acid, Chyme stays in stomach until adequate protein digestion has occurred. This is why you feel less hungry between meals
- 4. if you have eaten some protein. The chyme is kept in the stomach by the pyloric sphincter. C. SMALL INTESTINE A.Final area where most digestion occurs and absorption begins. Physical – villi and microvilli help separate food particles Chemical – where many enzymes complete the digestive process, many enzymes from accessory glands (liver, gall bladder, and pancreas) are dumped into the SI to help with digestion SMALL INTESTINE – STRUCTURE The small intestine is a long tube (7 m) in length and 2.5 cm in diameter with a total inner surface area of 30 m2 (due to the villi and microvillus). The SI is also divided into three sections: a) Duodenum b) Jejunum c) Ileum Duodenum: - first 25 cm portion - means 12 fingers in Latin (duo = 2, den = 10) - Pancreas and liver dump enzymes here to help digestion - most digestion occurs here - produces intestinal enzymes: maltase maltose peptidase polypeptides Chyme leaves the stomach through the pyloric sphincter where it is mixed with intestinal and pancreatic enzymes, bile and sodium bicarbonate, which neutralizes the acidic chyme. Accessory glands: Pancreas: - releases sodium bicarbonate to neutralize acidic chyme (PH 2.5 8) - releases digestive enzymes: pancreatic amylase starch
- 5. Lipase lipids Trypsin polypeptides These enzymes, as well as intestinal enzymes, have an optimal pH = 7.5, Therefore need to have the chyme neutralized before they can work properly. Liver: - 1.5 kg organ - secretes Bile (bile salts) these help emulsify (separate) fats which increases the surface area, enabling lipases to break down lipids more efficiently. The liver performs a vast number of functions (500), including production of bile from cholesterol, recycling of red blood cells, glycogen storage, storage of fat-soluble vitamins, deamination of amino acids, and detoxification of poisons. Everything that enters the body must go through the liver to be cleared. Gall bladder: - small sac near liver stores bile. 3. Absorption of nutrients Stomach: - small amounts of water- alcohol some medicines, e.g. aspirin Small intestine: jejunum - where most of the absorption takes place. Ileum: where the remaining nutrients are absorbed Absorption is greatly aided by the folded interior structure of the intestine, particularly due to the presence of the villi and microvilli. Structure of Villi: - tiny finger like projections lining the interior of the intestines - contain two types of vessels: capillaries – tiny blood vessels - collect water soluble nutrients glucose, amino acids
- 6. lacteal - contain lymph - collect products of fat digestion fatty acids and glycerol Final products of digestion (or what is absorbed) Macromolecule Digestion starts Digestion complete Final product Starch (CHO) mouth - amylase duodenum (SI) glucose Protein stomach HCl + pepsin duodenum (SI) amino acids Lipids duodenum bile + lipase duodenum (SI) fatty acids + Glycerol small molecules like vitamins, minerals, natural glucose and amino acids do not need to be digested and are easily absorbed by the small intestine. Water is absorbed throughout the alimentary (GI) tract but the majority of water absorption occurs in the large intestine also known as the Colon. The Colon – the large intestine (the bowel) Structure: - 1.5 m in length, 5 cm in diameter (twice the diameter of SI) - made up of four sections: Ascending Transverse Descending Sigmoid process -the colon ends with the rectum Function: - main job is to reabsorb water- bacteria here produce vitamins k. 4. Egestion of waste Cellulose: main component of feces, along with living and dead bacteria and water. - Fiber, found in plant cell walls, cannot be digested by humans Feces: - waste is stored in rectum- removed by body removing possible toxic materials.
- 7. Egestion controlled by anal sphincter which allows feces to leave rectum through the anus. Toilet training is learning how to control the anal sphincter. Small Intestine Enzymes 1. Cholecystokinin – Stimulates digestion of proteins and fats 2. Secretin – Controls secretion of duodenum and osmoregulation 3. Sucrase – Convertssucrose to disaccharides and monosaccharide 4. Maltase – Converts maltose to glucose 5. Lactase – Convertslactose to glucose and galactose 6. Isomaltase – Converts maltose to isomaltose Stomach Enzymes Pepsin is the main gastric enzyme. It breaks proteins into smaller peptide fragments. Gelatinase degrades type I and type V gelatin and type IV and V collagen, which are proteoglycans in meat. Gastric amylase degrades starch, but is of minor significance. Gastric lipase is a tributyrase by its biochemical activity, as it acts almost exclusively on tributyrin, a butter fat enzyme. Pepsin enzyme is secreted by gastric glands Renin enzyme change the liquid milk to solid Mouth Enzymes 1. Ptyalin – Converts starch to simple soluble sugars 2. Amylase – Convertsstarch to soluble sugars 3. Betaine – Maintainscell fluid balance as osmolytes 4. Bromelain – Anti-inflammatory agent, tenderizes meat Pancreas Enzymes 1. Pancreatic lipase – Degrades triglycerides into fatty acids and glycerol 2. Chymotrypsin – Converts proteins to aromatic amino acids 3. Carboxypeptidase – Degradation of proteinsto amino acids 4. Pancreatic amylase – Degradation of carbohydrates to simple sugars
- 8. 5. Elastases – Degrade the protein elastin 6. Nucleases – Conversion of nucleic acids to nucleotides and nucleosides 7. Trypsin – Converts proteins to basic amino acids 8. Steapsin – Breakdownof triglycerides to glycerol and fatty acids 9. Phospholipase – Hydrolyzesphospholipidsinto fatty acids and lipophilic substances. WEBSITES: http://www.medtropolis.com/VBody.asp http://www.innerbody.com/htm/body.html http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/smallgut/anatomy.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FramesVersion.html