CHAP24_2402 - CHAPTER 24 1 Biology 2402 Anatomy and...

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C H A P T E R 2 4 1 Biology 2402 Anatomy and Physician Lecture CHAPTER 24 THE DIGESTIVE SYSTEM
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C H A P T E R 2 4 2 THE DIGESTIVE SYSTEM Why do we need food? Why do we need the food broken down into molecules small enough to cross the plasma membrane? (Food is the source of energy that drives the chemical reactions occurring in every cell; and provides matter that is used to form new tissue or to repair damaged tissue. Food as it is consumed, is not in a state suitable for use as an energy source by any cell; Therefore must be broken down into molecules small enough to be transported through the plasma (cell) membranes.) Digestion - The breaking down of large food molecules into molecules small enough for use by body cells. Absorption - The passage of these smaller molecules into blood and lymph. Digestive System : The organs that collectively perform the above function. - The digestive system, with the help of the circulatory system, acts like a gigantic “meals on wheels,” providing nourishment to over a hundred trillion “customer” cells in the body. - It also has its own quality control and waste disposal system. Two Main Groups of the Organs of Digestion (1) Gastrointestinal (GI) tract or Alimentary Canal A continues tube, extends from the mouth to the anus - open to the outside at each end. (Dietary material in the lumen (inside cavity) of this tube have not yet
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C H A P T E R 2 4 3 truly entered the body). Organs of the Gastrointestine Tract : (1) Mouth (2) Pharynx (3) Esophagus (4) Stomach (5) Small intestine (6) Large intestine Accessary structures (1) Teeth - Aid physical breakdown of food (2) Tongue - Assists in chewing and swallowing (3) Salivary glands - Never come in contact with food (4) Liver - Never come in contact with food (5) Gallbladder - Never come in contact with food (6) Pancreas - Never come in contact with food Never come in contact with food, but produce/store secretions that aid in the chemical breakdown of food. flow into the tract through ducts. Gastroenterology : The medical specialty that deals with the structure, function, diagnosis, and treatment of diseases of the stomach and intestine. Proctology : The medical specialty that deals with the diagnosis and treatment of disorders of the rectum and anus. OVERVIEW OF DIGESTIVE PROCESSES (Six basic activities through which the digestive system prepares for consumption by the cells): 1. Ingestion - taking food into the mouth (eating).
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C H A P T E R 2 4 4 2. Secretion - Cells within the walls of the GI tract and accessory organs secrete a total of about 9 liters per day of water, acids, buffers, and enzymes into the lumen of the tract. 3. Mixing and Propulsion - Alternating contraction and relaxation of smooth muscles in the walls of the GI tract mix food and secretions and propel them toward the anus. 4.
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This note was uploaded on 03/10/2012 for the course BIOL 2403 taught by Professor Campbell during the Spring '12 term at Texas Pan American.

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CHAP24_2402 - CHAPTER 24 1 Biology 2402 Anatomy and...

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