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lecture_notes_32_(ta)_2 - Lecture 32...

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Lecture 32: Gastrointestinal/Digestive Physiology II The Mouth (or Oral Cavity) – is composed of (Figure 16-5) : (1) Lips - guide and contain food in the mouth; also serve in speech. (2) Palate - roof of the oral cavity; separates oral cavity from nasal passage ( OR CAVITY ’) . The palate allows chewing and breathing to occur simultaneously. ( BUT , WE CAN T BREATHE AND SWOLLOW SIMULTANEOUSLY ( DESPITE ATTEMPTS BY OUR PRESIDENT )) hard palate - toward front, made of bone. soft palate - toward back, no bone ( INVOLVED IN SNORIING ) cleft palate - failure of the palate to fuse along the midline (3) Uvula (‘ UV - U - LA ’) - soft tissue that hangs from the rear of the mouth. The uvula seals off the nasal passage during swallowing. (4) Tongue - forms the floor of the oral cavity and guides food during chewing and swallowing. The tongue is also important for speech. (5) Teeth - begin the digestive process by chewing or masticating the food. Enamel (strongest structure in the body) seals the teeth. (6) Salivary Glands - secrete saliva; 3 major pairs (Figure 16-5) : sublingual ( VERY LOW ) submandibular parotid ( IN BACK ) Saliva - 99.5% H 2 O, 0.5% electrolytes and proteins (enzymes). The most important proteins are: (*) amylase - begins the breakdown of polysacharides (carbohydrate) into maltose ( REMEMBER , PROTEIN BREAKDOWN BEGINS IN THE STOMACH ) mucus - moistens food and provides lubrication lysozyme - lyses or destroys bacteria
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The Pharynx and Esophagus Pharynx – is located at the rear of the mouth and serves as a common passageway for the digestive system and for the respiratory system (Figure 16-5) . The tonsils are located in the walls of the pharynx. ( USED TO BE REMOVED ) Esophagus – is a muscular tube that extends between the pharynx and the stomach. The esophagus contains 2 sphincters. ( IT IS SMALLER THAN THE TRACHEA , AND IS 9-10 INCHES LONG ) upper sphincter - (pharyngoesophageal sphincter) is normally closed to prevent air from entering esophagus (prevents excessive eructation (“ BURPING ”) ) lower sphincter - (gastroesophageal sphincter) is normally closed to prevent acid reflux from stomach. Swallowing - refers to the entire process of moving food from the mouth through the esophagus and into the stomach. It is an all-or-none reflex that is initiated when a food bolus ( A is pushed by the tongue into the pharynx (Figure 16-7) .
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lecture_notes_32_(ta)_2 - Lecture 32...

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