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Digestive System.  The digestive system is responsible for the physical and chemical breakdown of food so it can be taken into the bloodstream and used.

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Presentation on theme: "Digestive System.  The digestive system is responsible for the physical and chemical breakdown of food so it can be taken into the bloodstream and used."— Presentation transcript:

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 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 The Digestive System includes:

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

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

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

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

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


11  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  Salivary Glands


13  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 Pharynx or Throat

14  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 In the esophagus:

15 ature=player_detailpage Normal Swallow Animation - Thick and Easy Dysphagia - YouTube

16  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 Esophagus


18  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  Stomach


20  Circular muscle between the esophagus and stomach  Closes after food enters the stomach  Prevents food from going back up into the esophagus Cardiac Sphincter


22  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 Pyloric Sphincter


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

25  Juices contain hydrochloric acid  Kills bacteria  Facilitates the absorption of iron  Activates the enzyme pepsin Gastric Juices

26  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 Gastric Juices

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

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

29  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. Small Intestines--Duodenum

30  Eight feet long  Forms the middle section of the small intestine Small Intestines--Jejunum

31  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. Small Intestines--Ileum

32  Completes the process of digestion  Absorbs the products of digestion into the bloodstream for use by body cells Functions of the Small Intestines:

33  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 Intestinal Juices of the Small Intestines

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

35  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 Pancreatic Juice

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

37  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 Small Intestine—Blood Capillaries

38  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 Small Intestines--Lacteals

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

40  Final section of the alimentary canal  About 5 feet long and about 2 inches in diameter Large Intestines

41  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 Large Intestines--Functions

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


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

45  Transverse colon: extends across the abdomen, below the liver and stomach, but above the small intestine Large Intestine--Sections

46  Descending colon: extends down the left side of the body Large Intestines--Sections

47  Sigmoid colon:  Connects with descending colon  S-shaped section that joins with the rectum Large Intestines--Sections

48  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 Large Intestines--Sections

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

50 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 clotting of 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 Functions of the Liver:

51  Gallbladder:  1. Small muscular sac  2. Located under the liver and attached to it by connective tissue  3. Stores and concentrates bile, which it receives from the liver  4. When the bile is needed in the digestive tract to emulsify fats, it contracts and pushes the bile through the common bile duct into the duodenum Accessory Organs

52  Pancreas:  1. Fish-shaped organ located behind the stomach  2. Produces pancreatic juices  a. Juices enter duodenum through pancreatic duct  b. Contain enzymes to digest food  (1) Pancreatic amylase or amylopsin to break down sugars  (2) Trypsin and chymotrypsin to break down proteins  (3) Lipase or steapsin to act on fats  3. Produces insulin  a. Secreted into the bloodstream  b. Regulates the metabolism or burning of carbohydrates to convert glucose (blood sugar) to energy Accessory Organs

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