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Digestive System

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  1. Digestive System

  2. The digestive system is responsible for the physical and chemical breakdown of food so it can be taken into the bloodstream and used by body cells and tissues.

  3. The Digestive System includes: • The Alimentary Canal: • Long muscular tube • Begins at the mouth and includes the pharynx, esophagus, stomach, small intestines, large intestines, and the anus. • The Accessory Organs: • The salivary glands, tongue, teeth, liver, gallbladder, and pancreas

  4. Where does digestion start? • Mouth, buccal, or oral cavity • A. Receives food as it enters the body • B. Actions in the mouth • 1. Food is tasted • 2.Brokendown physically by the teeth • 3. Lubricated and partially digested by saliva • 4. Swallowed

  5. Teeth Special structures in the mouth 2. Break down food physically by chewing and grinding the food, a process called mastication

  6. Tongue Muscular organ 2. Contains special receptors called tastebuds that allow person to taste sweet, salt, sour, and bitter sensations 3. Also aids with chewing and swallowing of food

  7. Within the mouth: • Hard palate • 1. Bony structure that forms the roof of the mouth • 2. Separates the mouth from the nasal cavities

  8. Soft palate • 1. Located behind the hard palate • 2. Separates the mouth from the nasopharynx

  9. Uvula • (a) Cone-shaped muscular structure • (b) Hangs from the middle of the soft palate • (c) Prevents food from entering the nasopharynx during swallowing

  10. Salivary Glands • 1. Three pairs of glands • Parotid, sublingual, and submandibular • 2. Produce a liquid called saliva • (a) Lubricates the mouth during speech and chewing • (b) Moistens food so it can be swallowed easily • (c) Also contains an enzyme called salivary amylase • aa. Substance speeding up a chemical reaction • bb. Begins the chemical breakdown of carbohydrates or starches into sugars that can be taken into the body

  11. Pharynx or Throat A. After the food is chewed and mixed with saliva, it is called a bolus and it enters the pharynx or throat B. Tube that carries both air and food C. Carries the air to the trachea or windpipe D. Carries food to the esophagus

  12. In the esophagus: When bolus is swallowed, muscle action causes the epiglottis to close over the larynx 2. Prevents bolus from entering respiratory tract 3. In this way, the bolus enters the esophagus

  13. Normal Swallow Animation - Thick and Easy Dysphagia - YouTube www.youtube.com/watch?v=1YfO11Pry6Y&feature=player_detailpage

  14. Esophagus • Muscular tube dorsal to the trachea • Receives bolus from the pharynx and carries it to the stomach • Relies on a rhythmic, wavelike involuntary movement of its muscles, called peristalsis, to move the food in a forward direction

  15. Stomach • Enlarged part of the alimentary canal • Receives the food from the esophagus • Mucous membrane lining contains folds called rugae, which disappear as the stomach fills with food and expands

  16. Cardiac Sphincter • Circular muscle between the esophagus and stomach • Closes after food enters the stomach • Prevents food from going back up into the esophagus

  17. Pyloric Sphincter • Circular muscle between the stomach and small intestine • Keeps food in the stomach until it is ready to enter the small intestine • Food usually remains in the stomach for about one to four hours

  18. Gastric Juices • Produced by glands in the stomach • Converts food into a semi fluid material called chyme

  19. Gastric Juices • Juices contain hydrochloric acid • Kills bacteria • Facilitates the absorption of iron • Activates the enzyme pepsin

  20. Gastric Juices • Contain enzymes: • Lipase, which begins the chemical breakdown of fats • Pepsin, which starts protein digestion • In an infant, the enzyme rennin is secreted • 1) Aids in the digestion of milk • 2) Not present in an adult

  21. Small Intestine • Coiled section of the alimentary canal about 20 feet long and 1 inch in diameter • Receives food, in form of chyme, from stomach

  22. Small Intestines There are three sections: Duodenum—first 9-10 inches Jejunum—next 8 feet Ileum—final 12 feet

  23. Small Intestines--Duodenum The first 9-10 inches Bile from the gallbladder and liver enter this section through ducts or tubes Pancreatic juices from the pancreas also enter this section through ducts or tubes.

  24. Small Intestines--Jejunum Eight feet long Forms the middle section of the small intestine

  25. Small Intestines--Ileum Final 12 feet of the small intestine Connects with the large intestine at the cecum Circular muscle called the ileocecal valve separates the ileum and cecum and prevents food from returning to the ileum.

  26. Functions of the Small Intestines: • Completes the process of digestion • Absorbs the products of digestion into the bloodstream for use by body cells

  27. Intestinal Juices of the Small Intestines • Produced by the small intestine • Contain the enzymes maltase, sucrase, and lactase, which break down sugars into simpler forms • Contain enzymes known as peptidases, which complete the digestion of proteins • Contain the enzyme steapsin, which aids in the digestion of fat

  28. Bile Liquid that enters small intestine from liver and gallbladder 2. Emulsifies or physically breaks down fats

  29. Pancreatic Juice 1.Liquid that enters small intestine from pancreas 2. Contains enzymes that complete the process of digestion A) Pancreatic amylase or amylopsin, which acts on sugars B) Trypsin and chymotrypsin, which act on proteins C) Lipase or steapsin, which acts on fats

  30. Small Intestine--Villi • Fingerlike projections that line wall of small intestine • Allow food to be absorbed or taken into bloodstream • Contain blood capillaries and lacteals

  31. Small Intestine—BloodCapillaries • Blood capillaries absorb the digested nutrients and carry them to the liver where they are stored or released into general circulation for use by body cells

  32. Small Intestines--Lacteals • Lacteals pick up most of the digested fats and carry them to the thoracic duct in the lymphatic system, which releases them into the circulatory system

  33. Small Intestines When food has completed its passage through the small intestine only wastes, indigestible materials, and excess water remain

  34. Large Intestines • Final section of the alimentary canal • About 5 feet long and about 2 inches in diameter

  35. Large Intestines--Functions • Absorption of water and any remaining nutrients • Storage of indigestible materials before they are eliminated from the body • Synthesis (formation) and absorption of some B-complex vitamins and vitamin K by bacteria present in intestine • Transportation of the waste products out of the alimentary canal

  36. Large Intestines--Sections • Cecum: • First section • Connects with the ileum of the small intestine • Contains a small projection called the vermiform appendix

  37. Large Intestines--Sections Ascending colon: continues up on the right side of the body from the cecum to the lower part of the liver

  38. Large Intestine--Sections • Transversecolon: extends across the abdomen, below the liver and stomach, but above the small intestine

  39. Large Intestines--Sections • Descending colon: extends down the left side of the body

  40. Large Intestines--Sections • Sigmoid colon: • Connects with descending colon • S-shaped section that joins with the rectum

  41. Large Intestines--Sections • Rectum: • Final 6 to 8inches • Storage area for the indigestibles or wastes • Has a narrow canal called the anal canal, which opens at a hole called the anus • Fecal material or stool, the final waste product of the digestive process

  42. Accessory Organs • Liver: • Largest gland in the body • Accessory organ for the digestive tract • Located under the diaphragm in the upper right quadrant of the abdomen

  43. Functions of the Liver: • 1. Secretes bile • a. Used to emulsify or physically break up fats b. Also makes fats water soluble, which is necessary for absorption • 2. Stores sugar in the form of glycogen a. Glycogen is converted to glucose b. Released into the bloodstream when additional blood sugar is needed • 3. Stores iron and certain vitamins • 4. Produces heparin, a substance that prevents clotting of the blood • 5. Produces blood proteins such as fibrinogen and prothrombin, which aid in the clottingof blood • 6. Produces cholesterol • 7. Detoxifies(renders less harmful) substances such as alcohol and pesticides, and destroys bacteria that have been taken into the blood from the intestine