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Digestive System Parts And Function


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Published in: Health & Medicine

Digestive System Parts And Function

  1. 1. Digestive System Parts and Function
  2. 2. Digestion <ul><li>All organisms are composed of four complex biological molecules: lipids (or fats), proteins, carbohydrates, and nucleic acids. </li></ul><ul><li>For consumers such as humans, these molecules must be broken down into their component parts. </li></ul><ul><ul><li>Lipids to fatty acids, proteins to individual amino acids, and carbohydrates into simple sugars </li></ul></ul><ul><li>The chemical breakdown of complex biological molecules into their component parts is the process of digestion. </li></ul>
  3. 3. The digestive system <ul><li>In most animals the digestive system is made up of a tube (alimentary canal) that runs more or less the length of the body. </li></ul><ul><li>Generally the food moves in one direction and different parts are responsible for doing different jobs in the digestive process. </li></ul><ul><li>There are also accessory organs that are important in digestion that connect to the alimentary canal via ducts. </li></ul>
  4. 4. Principle Parts of Alimentary Canal <ul><li>Mouth- mechanical breakdown of food; tasting; secretion of salivary glands (salivary amylase) </li></ul><ul><li>Esophagus- muscular tube that connects the mouth with the stomach </li></ul><ul><li>Stomach- large muscular storage organ; functions in storage, mixing, some secretions (acid and pepsinogen) </li></ul><ul><li>Small intestine (3 parts) </li></ul><ul><ul><li>Duodenum, jejunum, ileum </li></ul></ul><ul><ul><li>Receives bile, pancreatic amylase, other secretions; absorption of nutrients (most sugars absorbed here) </li></ul></ul><ul><li>Large intestine- reabsorption of water; bacteria in colon produce Vit. K </li></ul><ul><li>Anus- external opening surrounded by sphincter muscle </li></ul>
  5. 5. Accessory Organs Connected to Digestive System <ul><li>Liver- has many functions including regulation of amino acids in blood, production of glycogen (a storage molecule) and bile, converting ammonia to urea </li></ul><ul><li>Pancreas- secretion of amylase and insulin (lack on insulin may cause diabetes) </li></ul><ul><li>Gall Bladder- storage of bile </li></ul>
  6. 6. <ul><li>Salivary Glands </li></ul><ul><li>Esophagus </li></ul><ul><li>Stomach </li></ul><ul><li>Pancreas </li></ul><ul><li>Large Intestine </li></ul><ul><li>Appendix </li></ul><ul><li>Small intestine </li></ul><ul><li>Gall Bladder </li></ul><ul><li>Liver </li></ul>
  7. 7. Connections to the Circulatory System <ul><li>Mesenteric Veins- veins connected to capillary bed closely tied with the intestine </li></ul><ul><li>Hepatic Portal System- major blood vessel that takes blood from the intestine to the capillary bed in the liver </li></ul><ul><li>Circulatory system- major system that transports nutrients to the rest of the body </li></ul><ul><ul><li>Absorption of nutrients from the small intestine occurs with the aid of villi and microvilli in the small intestine which increase surface area for diffusion </li></ul></ul>
  8. 8. The Villi of the small intestine
  9. 9. Enzymes <ul><li>They are biological catalysts which greatly increase the rate of a chemical reaction but are not themselves changed during the process </li></ul><ul><li>Enzymes are central in the digestion of many substances including carbohydrates, fats and proteins. </li></ul><ul><li>In most animals, the digestive enzymes are secreted into a special extracellular (outside of the cells) cavity called a gut where digestion actually takes place </li></ul><ul><ul><li>These smaller molecules can then be absorbed by the circulatory system and distributed to cells throughout the body. </li></ul></ul>
  10. 10. Importance of Proteins <ul><li>Proteins are important as a structural element in bones, cartilage, hair, feathers, nails, and cell membranes. </li></ul><ul><ul><li>They are also important as enzymes, hormones, antibodies, and in oxygen transport in red blood cells. </li></ul></ul><ul><li>Proteins are formed by the linkage of amino acids into polypeptides. </li></ul>
  11. 11. Digestion of Proteins <ul><li>Any enzyme that digests proteins is called a protease </li></ul><ul><li>Chemical digestion of proteins begins in the stomach </li></ul><ul><ul><li>The stomach is very acidic (has a low pH, 1.5 - 7) </li></ul></ul><ul><li>Pepsin is the primary digestive enzyme in the stomach </li></ul><ul><li>The small intestine carries out further digestion with trypsin, which is secreted by the pancreas </li></ul><ul><li>As proteins are digested, the polypeptide chains unravel and break up into small chains of amino acids called peptides </li></ul>
  12. 12. Importance of Lipids <ul><li>They are fats and oils which are a fundamental component of cell membranes and may be used for energy storage or insulation </li></ul><ul><li>A characteristic feature is that they do not dissolve in water </li></ul>
  13. 13. Digestion of Lipids <ul><li>It begins in the small intestine by making the molecules more compatible with water so that the digestive enzymes can access them. </li></ul><ul><ul><li>This is accomplished by breaking up the lipid into small droplets which can be distributed in the water of the small intestine </li></ul></ul><ul><ul><ul><li>This process is referred to as emulsification </li></ul></ul></ul><ul><ul><li>Bile which is produced by the liver, stored in the gall bladder and pumped into the small intestine when lipids are present is responsible for emulsification </li></ul></ul><ul><li>Once emulsified, they may be digested into their subunits (glycerol and fatty acids) by digestive enzymes called lipases. </li></ul><ul><ul><li>They are produced in the pancreas and secreted into the small intestine </li></ul></ul>
  14. 14. Importance of Carbohydrates <ul><li>These include simple sugars such as glucose and sucrose and polysaccharides such as starch and cellulose </li></ul><ul><li>They are important as structural compounds and as a source of energy that can be used as ATP </li></ul><ul><li>Starch is a complex polysaccharide made in plants cells for the storage of energy </li></ul><ul><ul><li>Foods such as potatoes and pumpkins are rich in starch and can be good sources of energy </li></ul></ul><ul><li>Cellulose is one of the most common carbohydrates and can be found in the cell walls of plants </li></ul><ul><ul><li>Human digestive system is unable to break down cellulose and is the largest component of dietary fiber </li></ul></ul>
  15. 15. Digestion of carbohydrates <ul><li>The digestion begins by converting polysaccharides (long chains of simple sugars) and disaccharides (two sugars linked together) into monosaccharides (simple sugar units) that can be absorbed by body cells </li></ul><ul><ul><li>It begins in the mouth and is completed in the small intestine (they are not digested in the stomach) </li></ul></ul><ul><li>Amylase is the enzyme responsible for digesting starch </li></ul><ul><ul><li>It can be found in the mouth in one’s saliva as well as in the small intestine secreted by the pancreas </li></ul></ul>