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Digestive System

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  • 1. DIGESTIVE SYSTEM Before your body can use nutrients in the food you consume, the nutrients must be broken down physically and chemically . This process of breaking down food into molecules the body can use called digestion .
  • 2. THE GASTROINTESTINAL TRACT
    • DIGESTION IS THE BREAKDOWN OF FOOD INTO SIMPLER MOLECULES THAT CAN BE ABSORBED AND USED BY THE BODY.
    • The Digestion System is actually LONG, HALLOW-TUBE called the Gastrointestinal Tract or GI TRACT or DIGESTIVE TRACT . It begins with the mouth and winds through the body to the anus- “ In one end and out the other end “.
    • THE DIGESTION SYSTEM INCLUDES THE MOUTH, PHARYNX, ESOPHAGUS, STOMACH, SMALL INTESTINE, AND LARGE INTESTINE.
    • SEVERAL MAJOR ORGANS, (EXOCRINE GLANDS ), ALONG THE DIGESTIVE TRACT AID DIGESTION, INCLUDING THE SALIVARY GLANDS, THE PANCREAS, AND THE LIVER, ADD THEIR SECRETIONS TO THE DIGESTION SYSTEM, BUT ARE NOT PART OF THE GI TRACT.
  • 3.
    • THREE ACTIVITIES ARE INVOLVED IN THE DIGESTIVE PROCESS :
      • MECHANICAL DIGESTION
      • CHEMICAL DIGESTION
      • ABSORPTION
    • The FIRST TASK of the Digestion System is to BREAK DOWN food into fine PULP ( MECHANICAL DIGESTION ), to increase surface area and expose more food molecules to the actions of Digestive Chemicals .
    • The process of Mechanical Digestion breaks food into tiny pieces WITHOUT changing the CHEMICAL STRUCTURE of the food.
  • 4.
    • The SECOND TASK of the Digestive System is to CHEMICALLY act on food, breaking it down to smaller and smaller particles . The molecules must be small enough and chemically simple enough to be absorbed into the blood stream . Example: STARCHES to simple SUGARS, PROTEINS to AMINO ACIDS .
    • The LAST TASK of the Digestion System is to ABSORB the small molecules and pass them to the BLOODSTREAM AND LYMPH VESSELS for distribution to the rest of the body.
    • Humans are OMNIVORES who eat both plants and animals for energy and our digestion system is adapted to process both vegetable and animal materials.
  • 5. THE MOUTH
    • MECHANICAL AND CHEMICAL DIGESTION BOTH BEGIN IN THE MOUTH.
    • CHEWING is the first step in mechanical digestion.
    • During chewing, Salivary Glands produce SALIVA , a mixture of water, mucus, and a digestive enzyme called SALIVARY AMYLASE , which mixes with the chewed food . Enzymes in the saliva kill bacteria and begin the process of chemical digestion by breaking down starches to sugars . Saliva is produced by three sets of glands located near the mouth .
  • 6. Salivary Amylase
    • The enzymes present in saliva which begins the process of starch digestion in the mouth
  • 7.
    • The mucus in the saliva softens and lubricates food and helps hold the food together . The Salivary Amylase begins the chemical digestion of carbohydrates by breaking down some starch into disaccharide maltose
    • human TEETH are well adapted for chewing many kinds of food . The 32 teeth of the normal adult have three basic shapes, each with a different function :
      • INCISORS - SHARP FRONT TEETH USED FOR BITTING INTO SND TEARING PIECES OF FOOD.
      • CANINES – POINTED TEETH ( VAMPIRE ) NEXT TO INCISORS , USED TO TEAR OR SHRED FOOD.
      • MOLARS – TEETH AT THE BACK OF MOUTH, HAVE LARGE FLAT SURFACES THAT CRUSH AND GRIND FOOD.
  • 8.
    • Every tooth has TWO main parts : the CROWN and the ROOT.
    • A tooth is made of FOUR LAYERS of TISSUE : ENAMEL, DENTIN, CEMENTUM, AND PERIODONTAL MEMBRANE ( LIGAMENT ).
    • The CROWN is covered by ENAMEL , a calcium-containing materials THAT IS THE HARDEST SUBSTANCE IN THE BODY.
    • DENTINE a bone like tissue make up most of the inside of a tooth .
  • 9.
    • CEMENTUM in a tine layer covers the dentine of the root.
    • The Periodontal Ligament holds the tooth in its socket.
    • The tongue helps to keep the food between the chewing surfaces of the Upper and Lower teeth by manipulating it against the HARD PALATE , the bony membrane covered roof of the mouth . This structure is different from the SOFT PALATE , an area located just behind the Hard Palate.
  • 10. ESOPHAGUS
    • Once the teeth and salivary glands have completed the initial processing , the food is ready to be SWALLOWED.
    • Gathering the food together in a ball called a BOLUS ; the TONGUE pushes it toward the back of the mouth and into the PHARYNX .
    • THE PHARYNX IS AN AREA AT THE BACK OF THE THROAT THAT CONNECTS THE NOSE AND MOUTH TO THE DIGESTION AND RESPIRATORY TRACTS
  • 11.
    • In the pharynx, the GI tract and the respiratory system cross each other.
    • As the tongue moves food into the pharynx, it presses down on a SMALL FLAP of cartilage called the EPIGLOTTIS . When the epiglottis is depressed, it CLOSES the entrance to the respiratory tract and guides the food down to GI Track.
    • FOOD ( THE BOLUS ) MOVES FROM THE PHARYNX INTO THE ESOPHAGUS , A 25 cm LONG MUSCULAR TUBE THAT CONNECTS THE PHARYNX WITH THE STOMACH
  • 12.
    • Once the bolus enters the esophagus , MUSCLES in the esophagus wall move food toward the stomach . The esophagus has two muscle layers : a CIRCULAR LAYER that wraps around the esophagus and a LONGITUDINAL LAYER that runs the length of the tube.
    • WAVES OF MUSCULAR CONTRACTIONS CALLED PERISTALSIS ( payr- ih – stol- sis ) MOVE FOOD THROUGH the digestive tract.
    • Contraction of the muscles move the bolus to a valve called CARDIAC SPHINCTER VALVE where the esophagus joins the stomach . The Sphincter allows food to pass into the stomach but usually NOT letting it move back up into the esophagus .
  • 13. THE STOMACH
    • The partially digested food is now in the stomach .
    • The STOMACH IS A J-SHAPED MUSCULAR SAC WITH THICK EXPANDABLE WALLS LOCATED IN THE UPPER LEFT SIDE OF THE ABDOMINAL CAVITY, JUST BELOW THE DIAPHRAGM .
    • THE STOMACH IS INVOLVE IN BOTH MECHANICAL AND CHEMICAL DIGESTION .
    • The Stomach Walls are made up of layers of muscles that contract in OPPOSITE DIRECTION.
  • 14. Greater Curvature
    • The convex lateral surface of the stomach.
    • Parietal Cells - the cells in the stomach producing hcl to activate enzymes and make stomach contents acidic.
  • 15.
    • Mechanical Digestion occurs when the stomach walls contract strongly, mixing and churning the food. These contractions are responsible for the “ GROWLING ” noises our stomach makes , they are the loudest when we have an empty stomach .
    • Chemical Digestion in the stomach begins with the actions of HYDROCHLORIC ACID and an enzyme called PEPSIN . Both substance are secreted by GASTRIC GLANDS in the stomach. These Fluids that carry out the chemical digestion in the stomach are known as GASTRIC FLUIDS .
    • PEPSIN breaks down proteins into shorter chains of amino acids called PEPTIDES . PEPSIN works best in an acidic environment, which is provided by the hydrochloric acids
  • 16.
    • Another fluid secreted by glands in the stomach is MUCUS . Mucus lubricates food so that it can travel through the digestive tract more easily .
    • Mucus also COATS the walls of the stomach, protecting the muscle tissue from being broken down by other digestive fluids .
    • The inner lining of the stomach is a thick, wrinkled mucous membrane composed of epithelial cells . This membrane is dotted with small openings called GASTIC PITS , they are the open ends of GASTRIC GLANDS that release secretions into the stomach . Some of these glands secret mucus, some secretes digestive enzymes, and still other secret HYDROCHLORIC ACID . The mixture of these fluids form the Acidic Digestive Fluid.
  • 17.
    • Lives of stomach wall cells are short, they are replaces about every three days .
    • After about THREE HOURS ( 3-4 hours ) of mechanical and chemical treatment in the stomach , food is reduced to a soft pulp called CHYME ( kym ).
    • CHYME IS A THICK LIQUID MADE UP OF PARTIALLY DIGESTED PROTEINS, STARCHES, VITAMINS, MINERALS AND ACIDS, AND UNDIGESTED SUGARS AND FATS.
    • At this point, the PYLORIC SPHINCTER VALVE between the stomach and small intestine opens , allowing small amounts of Chyme to pass into the small intestine.
    • By the time chime has left the stomach , MOST PROTEINS have been broken down into smaller Polypeptides . Sugars and Fats have NOT YET been chemically altered. Some stomach molecules have been broken down into Disscharides .
  • 18. THE SMALL INTESTINE
    • As chyme is push through the pyloric valve, it enters the DUODENUM , the first part of the small intestine .
    • The small intestine performs THREE major functions on Chyme that enters from the stomach .
    • THE SMALL INTESTINES DIGEST CARBOHYDRATES AND FATS, COMPLETES THE DIGESTION OF PROTEINS , AND ABSORB DIGESTED NUTRIENTS .
    • The small intestine is long ( 7 m ) but its diameter ( 2.5 cm ) is smaller than the large intestine . The small intestine consists of THREE PARTS :
    • DOUDENUM – THE FIRST SECTION ( 25 cm )
    • JEJUNUM – THE MIDDLE SECTION ( 2.5 cm )
    • ILEUM – MAKE UP THE REMAINIG PORTION .
  • 19. SMALL INTESTINE
    • The body’s major digestive organ.
    • The obligatory urinary output/day of an individual capable of removing wastes from the blood is 400-500 cc /day.
  • 20.
    • Some of the digestive fluids and enzymes that digest food in the small intestine comes from the glands located in the small intestine.
    • These glands produce enzymes that digest proteins and carbohydrates .
    • The PANCREAS , and organ located behind the stomach , secretes Pancreatic Fluid into the small intestine . The Pancreatic Fluid enters the small intestines through the Pancreatic Duct , which joins the common Bile Duct just before it enters the intestine .
    • Pancreatic Fluid contains enzymes that digest proteins, Fats, and Carbohydrates .
    • Pancreatic Fluid also contains SODIUM BICARBONATE , which neutralizes the Hydrochloric Acid in the Chyme ( from acid to a base ), protecting the small intestine.
  • 21.
    • The LIVER is a large brownish organ that lies above the stomach in the abdominal cavity . One of the functions of the liver is to secrete a yellow-brown liquid called BILE.
    • BILE is stored in a small sac called GALLBLADDER . The entrance of food into the small intestine stimulates the release of BILE to small intestine through a Duct .
    • Bile is produced by the liver and stored in the Gallbladder until needed.
    • FATS in the small intestine are broken down into smaller droplets of Bile.
    • One of the main functions of Bile is to dissolve cholesterol . Bile is a salt containing detergent and if the amount of salt in the bile is insufficient , sharp, painful crystals can form , known as GALLSTONES.
  • 22. ABSORPTION
    • MOST OF THE NUTRIENTS ARE ABSORBED INTO THE CIRCULATORY SYSTEM THROUGH THE CELLS THAT LINE THE SMALL INTESTINE.
    • THE INTERNAL SURFACE OF THE INTESTINE IS LINED WITH FINGERLIKE PROJECTIONS CALLED VILLI . The cells covering the Villi , in turn have extensions on their cell membranes called MICROVILLI .
    • Villi increase the surface area of the lining of the small intestine, making absorption more efficient .
    • NUTRIENTS ARE ABSORBED THROUGH CAPILLARES AND TINY LYMPH VESSELS CALLED LACTEALS IN THE VILLI .
  • 23.
    • CAPPILARIES absorb the Carbohydrates ( Monosaccharides ) and proteins ( Amino Acids ) and are carried to the liver.
    • The liver neutralizes many toxic substances in the blood and removes excess Glucose converting it to Glucogen for storage ( FAT ). The filtered blood then carries the nutrients to all parts of the body.
    • The tiny lymph vessels called lacteals absorb glycerol and fatty acids , which are carried through the lymph vessels and eventually to the bloodstream through lymphatic vessels near heart.
    • MOST OF THE NUTRIENTS USED BY THE BODY ARE ABSORBED THROUGH THE LINING OF THE SMALL INTESTINES.
  • 24. LARGE INTESTINE
    • AFTER ABSORPTION IN THE SMALL INSTETINES IS COMPLETE , UNDIGESTED MATERIALS LEAVES THE SMALL INTESTINE THROUGH A VALVE AND ENTERS THE LARGE INTESTINE OR COLON.
    • It is the final organ of the digestion and consists of FOUR MAJOR PARTS : ASCENDING COLON, TRANVERSE COLON, DESCENDING COLON, and SIGMOID COLON.
    • An organ called the APPPENDIX is located near the junction of the small and large intestine . The appendix is finger-shaped pouch, which does not serve any known function . If the appendix becomes infected with bacteria , resulting in appendicitis , the appendi x must be removed.
  • 25. LARGE INTESTINE
    • Its major function is to dry out indigestible food residue by absorbing water and consequently eliminating residues from the body as feces.
  • 26.
    • The large intestine , also called the Colon , is about 6 cm wide and 1.5 m long.
    • THE LARGE INTESTINE ABSORBS WATER FROM THE MATERIAL REMAINING IN THE DIGESTIVE TRACT .
    • WATER-SOLUBLE VITAMINS ARE ABSORBED ALONG WITH THE WATER, Vitamin K.
    • When most of the water has been removed from the undigested material, a solid waste matter , called FECES remains.
  • 27.
    • PERISTALSIS propel the feces through the large intestine and into the RECTUM , the last few inches of the large intestine . Feces collected in the rectum are eliminated through the ANUS .
    • Sometimes a disease or disorder prevents the large intestine from absorbing enough water – the result is diarrhea , or water feces . Severe Diarrhea can result in a loss of water , or Dehydration , that can be FATAL .
  • 28.
      • Bile - it is produced by the liver necessary to emulsify fats.
  • 29. Your Digestive System and How It Works
    • The digestive system is made up of the digestive tract—a series of hollow organs joined in a long, twisting tube from the mouth to the anus—and other organs that help the body break down and absorb food
  • 30.
    • Organs that make up the digestive tract are the mouth, esophagus, stomach, small intestine, large intestine—also called the colon—rectum, and anus. Inside these hollow organs is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tiny glands that produce juices to help digest food. The digestive tract also contains a layer of smooth muscle that helps break down food and move it along the tract.
  • 31.
    • Two “solid” digestive organs, the liver and the pancreas, produce digestive juices that reach the intestine through small tubes called ducts. The gallbladder stores the liver’s digestive juices until they are needed in the intestine. Parts of the nervous and circulatory systems also play major roles in the digestive system.
  • 32. Why is digestion important?
    • When you eat foods—such as bread, meat, and vegetables—they are not in a form that the body can use as nourishment. Food and drink must be changed into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which food and drink are broken down into their smallest parts so the body can use them to build and nourish cells and to provide energy.
  • 33. How is food digested?
    • Digestion involves mixing food with digestive juices, moving it through the digestive tract, and breaking down large molecules of food into smaller molecules. Digestion begins in the mouth, when you chew and swallow, and is completed in the small intestine.
  • 34. Movement of Food Through the System
    • The large, hollow organs of the digestive tract contain a layer of muscle that enables their walls to move. The movement of organ walls can propel food and liquid through the system and also can mix the contents within each organ. Food moves from one organ to the next through muscle action called peristalsis. Peristalsis looks like an ocean wave traveling through the muscle. The muscle of the organ contracts to create a narrowing and then propels the narrowed portion slowly down the length of the organ. These waves of narrowing push the food and fluid in front of them through each hollow organ.
  • 35.
    • The first major muscle movement occurs when food or liquid is swallowed. Although you are able to start swallowing by choice, once the swallow begins, it becomes involuntary and proceeds under the control of the nerves.
  • 36.
    • Swallowed food is pushed into the esophagus, which connects the throat above with the stomach below. At the junction of the esophagus and stomach, there is a ringlike muscle, called the lower esophageal sphincter, closing the passage between the two organs. As food approaches the closed sphincter, the sphincter relaxes and allows the food to pass through to the stomach.
  • 37.
    • The stomach has three mechanical tasks. First, it stores the swallowed food and liquid. To do this, the muscle of the upper part of the stomach relaxes to accept large volumes of swallowed material. The second job is to mix up the food, liquid, and digestive juice produced by the stomach. The lower part of the stomach mixes these materials by its muscle action. The third task of the stomach is to empty its contents slowly into the small intestine.
  • 38.
    • Several factors affect emptying of the stomach, including the kind of food and the degree of muscle action of the emptying stomach and the small intestine. Carbohydrates, for example, spend the least amount of time in the stomach, while protein stays in the stomach longer, and fats the longest. As the food dissolves into the juices from the pancreas, liver, and intestine, the contents of the intestine are mixed and pushed forward to allow further digestion.
  • 39.
    • Finally, the digested nutrients are absorbed through the intestinal walls and transported throughout the body. The waste products of this process include undigested parts of the food, known as fiber, and older cells that have been shed from the mucosa. These materials are pushed into the colon, where they remain until the feces are expelled by a bowel movement.
  • 40. Production of Digestive Juices
    • The digestive glands that act first are in the mouth—the salivary glands. Saliva produced by these glands contains an enzyme that begins to digest the starch from food into smaller molecules. An enzyme is a substance that speeds up chemical reactions in the body.
  • 41.
    • The next set of digestive glands is in the stomach lining. They produce stomach acid and an enzyme that digests protein. A thick mucus layer coats the mucosa and helps keep the acidic digestive juice from dissolving the tissue of the stomach itself. In most people, the stomach mucosa is able to resist the juice, although food and other tissues of the body cannot.
  • 42.
    • After the stomach empties the food and juice mixture into the small intestine, the juices of two other digestive organs mix with the food. One of these organs, the pancreas, produces a juice that contains a wide array of enzymes to break down the carbohydrate, fat, and protein in food. Other enzymes that are active in the process come from glands in the wall of the intestine.
  • 43.
    • The second organ, the liver, produces yet another digestive juice—bile. Bile is stored between meals in the gallbladder. At mealtime, it is squeezed out of the gallbladder, through the bile ducts, and into the intestine to mix with the fat in food. The bile acids dissolve fat into the watery contents of the intestine, much like detergents that dissolve grease from a frying pan. After fat is dissolved, it is digested by enzymes from the pancreas and the lining of the intestine.
  • 44. Absorption and Transport of Nutrients
    • Most digested molecules of food, as well as water and minerals, are absorbed through the small intestine. The mucosa of the small intestine contains many folds that are covered with tiny fingerlike projections called villi. In turn, the villi are covered with microscopic projections called microvilli. These structures create a vast surface area through which nutrients can be absorbed. Specialized cells allow absorbed materials to cross the mucosa into the blood, where they are carried off in the bloodstream to other parts of the body for storage or further chemical change. This part of the process varies with different types of nutrients.
  • 45. CARBOHYDRATES
    • Most digested molecules of food, as well as water and minerals, are absorbed through the small intestine. The mucosa of the small intestine contains many folds that are covered with tiny fingerlike projections called villi. In turn, the villi are covered with microscopic projections called microvilli. These structures create a vast surface area through which nutrients can be absorbed. Specialized cells allow absorbed materials to cross the mucosa into the blood, where they are carried off in the bloodstream to other parts of the body for storage or further chemical change. This part of the process varies with different types of nutrients.
  • 46.
    • The digestible carbohydrates—starch and sugar—are broken into simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining of the small intestine. Starch is digested in two steps. First, an enzyme in the saliva and pancreatic juice breaks the starch into molecules called maltose. Then an enzyme in the lining of the small intestine splits the maltose into glucose molecules that can be absorbed into the blood. Glucose is carried through the bloodstream to the liver, where it is stored or used to provide energy for the work of the body.
  • 47.
    • Sugars are digested in one step. An enzyme in the lining of the small intestine digests sucrose, also known as table sugar, into glucose and fructose, which are absorbed through the intestine into the blood. Milk contains another type of sugar, lactose, which is changed into absorbable molecules by another enzyme in the intestinal lining.