4 Food passes through the digestive tube in the following order Oral cavity pharynx esophagus(mouth) (throat) (gullet)Stomach small largeintestine intestineRectum anus
5 HUMAN DIGESTIVE SYSTEM Liver, pancreas and salivary glands lie outside of the digestive tract and they are called as accessory organs.Food is never found within the alimentary canal itself.These organs aid digestion by the secretion of digestive fluids.
7 THE MOUTH AND PHARYNXMechanical breakdown and chemical digestion occur.Chunks of food are bitten of with the teeth and ground into pieces small enough to swallowThe tongue moves and shapes the food mass in the mouthSaliva is secreted into the mouth by three pairs of salivary glands
9 TYPES OF SALIVA Thin, watery secretion that wets the food Thicker, mucuous secretion that acts as a lubricant and causes the food particles to stick together to form a food mass (bolus)
10 Saliva also contains a digestive enzyme called salivary amylase Saliva also contains a digestive enzyme called salivary amylase . (This enzyme breaks down starch, which is a polysacharide, into maltose, which is a disaccharide.)When the food has been chewed sufficiently , it is pushed by the tongue to the back of the throat, or pharynx. This starts the automatic swallowing reflex, which forces the food into the esophagus, the tube leading to the stomach.To prevent food and liquids from entering the larynx, it is automatically closed off during swallowing by a flap of tissue called epiglottis.At the same time, breathing stops momentarily and passageways to the nose, ears and mouth are blocked
11 THE ESOPHAGUSThe esophagus is a tube through which food passes from pharynx to the stomach.Beginning in the esophagus, the movement of food down the digestive tube is aided by alternate waves of relaxation and contraction in the muscular walls of the alimentary canal. This is called peristalsis.
13 THE ESOPHAGUSWhere the esophagus opens into the stomach , there is a ring of muscle called sphincter. There are two sphincters to isolate the stomach.Cardiac sphincteris located between the esophagus and the stomachPyloric sphincteris located between the stomach and the intestine
15 When the wave of peristalsis reaches the sphincter, it relaxes and opens, and the food (bolus) enters the stomach.During vomitting, a wave of peristalsis passes upward -reverse peristalsis- causing the cardiac sphincter to open, and the contents of the stomach to be “thrown up”
17 THE STOMACH The stomach is thick-walled muscular sac. Food is stored temporarily in the stomach.Mechanical breakdown and the partial digestion of protein occur.Churning of the stomach causes mechanical break down and helps the mixing of the food with its secretions.
19 GLANDS OF THE STOMACH Pyloric glands Secretes mucus Mucus protects the lining of the stomach from being digestedGastric glandsSecretes gastric juice(pH 1.5 to 2.5)GASTRIC JUICEPepsinogenInactive form of pepsin and activated by HClBreaks down large protein molecules into shorter chains of a.a called polypeptides.HClHCl kills the bacteria that are swallowed with foodActivates pepsinogen
25 THE STOMACHThe breakdown of starch by salivary amylase which begins in the mouth, continues for some time after the food mass reaches the stomach. Gradually however, the low pH of the acid in the stomach inactivates this enzyme and starch breakdown.
26 THE STOMACHThere are three mechanisms involved in stimulating the flow of gastric juice.The thought, sight, smell or taste of food stimulates the brain to send messages to the gastric glands, causing them to secrete moderate amounts of gastric juice
27 THE STOMACH2. Food touching the lining of the stomach stimulates the secretion of moderate amounts gastric juice.3. When a food mass enters the stomach, it stretches the stomach wall. The streching of the stomach wall, as well as the presence of proteins, caffeine, alcohol and certain other substances, stimulates the lining of the stomach to secrete a hormone called gastrin directly into the blood. Gastrin further stimulates the gastric glands in the stomach to secrete large amounts of gastric juice.
28 THE STOMACH Liquids pass through the stomach in 20 minutes or less. Solids on the other hand, must first be reduced to a thin, soupy liquid called chyme
29 Most of the digestion takes place FUNCTIONS OF THE SMALL INTESTINE: pyloric sphincter6.5 meters in lengthchyme2.5 cm in diameterduodenumjejenumileumMost of the digestion takes placeFUNCTIONS OF THE SMALL INTESTINE:Most of the chemical digestion takes place and completed in itIt is the site of absorption
31 THE SMALL INTESTINEIt has a number of structural features that increase the surface area for absorbtion.It is very longIts lining has many foldsThe lining is covered with millions of finger-like projections which are called villiThe epithelial cells that make up the intestinal lining have brush borders. In the brush borders, the membranes of cells that face into the intestinal opening have tiny projections called microvilli that further increase the surface area of the cells.
36 Within each villus , there is a network of blood capillaries and in the center of it there is a lacteal. Fatty acids and glycerol are absorbed into tiny lacteals of the lymphatic system.
37 THE SMALL INTESTINEAbsorption involves both diffusion and active transport.When food is present, the small intestine is in constant motion. This peristaltic movements have four effect:They squeeze chyme through the intestineThey mix the chyme with the digestive enzymesThey break down food particles mechanicallyThey speed up absorption of digestive end products by bringing the intestinal contents into contact with intestinal wall.
39 Chyme from the stomach is mixed with Pancreatic juicefrom pancreasIntestinal juice from glands in the wall of the intestineBile from the liver*** Fluids in the small intestine are generally alkaline
40 PANCREASPancreas is located in the abdominal cavity between stomach and duodenum.It is both endocrine and exocrine gland.It secretes insulin and glucagon form the Islets of LangerhanspH of pancreatic juice is 8.5
43 pass throuh the pancreatic duct PANCREATIC JUICEWhen the acidic chyme from the stomach enters the small intestine, it stimulates cells in the intestinal lining to secrete two hormonesCHOLECYSTOKININSECRETINstimulatesPancreas to secrete pancreatic juice and pancreatic enzymespass throuh the pancreatic ductonto the ampulla of vater in the duodenum part of the small intestine
46 PANCREATIC JUICE Enzymes Bicarbonate ions Amylase ProteasesLipaseBicarbonate ionsConverts the acidic chyme into alkaline solutionChyme is neutralised by HCO3- and turns into alkaline solution.H HCO H2 CO3Alkaline because medium of intestine is basicAcid from stomachBicarbonate from liver and pancreas
47 ENZYMES OF PANCREATIC JUICE Pancreatic Amylase:Starch + water maltose + dextrinamylase2. ProteasesTrypsinTrypsinogen trypsin(inactive) (active)chymotrypsinanterokinaseThey continue the break down of large protein molecules into amino acids begun in the stomachTrypsin and chymotrypsinPolypeptides + water peptide + amino acids
48 ENZYMES OF PANCREATIC JUICE 3. Lipaselipaselipid fatty acids + glycerol4 . NucleasesNucleic acids nucleotides
49 Digestion in small intestine (pancreatic juice) cells in intestinal liningAcidic chymeto secrete hormonesSecretin and cholecystokininstimulatePancreasto secretePancreatic juicePancreatic ductgiven toSmall intestine
51 BILE is secreted from liver stored and concentrated in gall bladder has no enzymeis alkalineconsists of water, ions, cholesterol and bile salts, pigmentsit passes from gall bladder to duodenum through the bile ductthe release of bile from the gall bladder is stimulated by cholecystokinin hormone.it aids in the digestion of fats and oils by breaking them up into tiny droplets. This is called emulsification. It increases the surface area for enzyme action.since bile is alkaline, it aids in neutralizing the acidic chyme from stomach.
52 Digestion in small intestine (bile from gall bladder) Hormone cholecystokininstored in theBile produced in the livergallbladderreleases bile into theBile ductopens toSmall intestine
58 INTESTINAL JUICE Peptides amino acids 2. Maltose 2 glucose The wall of the small intestine contain millions of intestinal glands, which secrete intestinal juice.Peptides amino acids2. Maltose 2 glucose3. Sucrose glucose+fructose4. Lactose glucose+galactosepeptidase(erepsin)maltasesucraselactase
62 HORMONAL CONTROL OF DIGESTION HORMONESOURCETARGET TISSUEACTIONFACTORS THAT STIMULATE RELEASEGastrinStomach(Mucosa)(Gastric glands)Stimulates gastric glands to secrete pepsinogenPresence of food in stomach and certain substances such as caffeineSecretinSmall intestine(Duodenum mucosa)PancreasSignals secretion of sodium bicarbonateAcidic chyme acting on mucosa of duodenum (small intestine)LiverStimulates bile secretionCholecytokininsStimulates release of digestive enzymesPresence of fatty acids and partially digested proteins in duodenum(small intestine)GallbladderStimulates emptying of bile
64 LARGE INTESTINEUndigested and unabsorbed materials pass from the small intestine through a sphincter into the large intestine.No digestion occursOn the right side of the abdomen, where the small intestine joins the large intestine, is a small pouch the appendix.(It plays no part in the HDS)The appendix becomes infected or inflamed, a condition known as appendicitis
65 FUNCTIONS OF THE LARGEReabsorbtion of water form the food mass ¾ of water is reabsorbed.If too much water is reabsorbed, constipation results.If too little water is reabsorbed , diarrhea results.2. The absorption of vitamins (vitamin K and Vitamin B) that are produced by bacteria that normally live in the large intestine.3. The elimination- removal of undigested and indigestible material from the digestive tract.
66 LARGE INTESTINEThis material consists of cellulose, bacteria, bile, mucus and worn-out cells from the digestive tract. As this material travels through the intestine, it becomes feces.Fecal matter is stored in the rectum and periodically eliminated, through the anus.
67 Check If Your Feces Are Healthy Dietary fibers and lactobacillus bifidus are essential for a healthy and comfortable life.The best feces are like bananas. They are modestly hard with no strong smell. Feces are like a barometer of your health and beauty. Check the following questions to see if you have a healthy feces or not.Do they float? They float point They sink pointsHow often do you evacuate? Once a day point Not everyday pointsHow hard are they? Like toothpaste point Hard pointsWhat color are your feces? Yellow point Dark brown pointsHow much do they weight? ( 2 pcs of feces a day, each about 2cm in diameter and about 15cm in length ) Over 200g point Below 200g pointsDo your feces smell? Not much point Bad smell pointsIf you score: 7 to 9 points You are quite healthy 10 to 12 points......Be careful what you eat everyday Take more dietary fibres. 13 to 14 points......Warning! If these conditions continue long, you should see a doctor.Like pebbles...2pointsLike paste....1 pointLike banana....1 pointVery hard....2 pointLiquid....2 pointLike mud....2 point