March 5 Lecture - March 5, 2009 The Digestive System The...

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March 5, 2009 The Digestive System The Teeth (Continued from previous lecture) - A third tooth bud is sometimes located below a permanent tooth o This may be induced to irrupt and fill the space where the adult tooth was lost (in place of a fake tooth) The Oral Cavity The Salivary Glands - There are three salivary glands located in the oral cavity o The parotid gland (located in the cheek, just below and in front the ear) o Submandibular glands (or submaxillary glands ) Located in the mandible Located at the angle of the jaw o Sublingual glands On the floor of the mouth, below the tounge - When salivary glands are stimulated, they produce copulous amounts of salivy - Events that stimulate salivary secretions o Physical factors (the presence of food) o Thermal factors (warming food enhances activity) o Olfactory activity o Psyche factor - The saliva that is in the mouth is the contribution of all three sets of glands - Over the course of a day, salivary glands produce 1-1.5 litres of saliva - Saliva is made up of o Mostly water o Some small amounts of proteins o Salts and electrolytes o Maltase An enzyme that breaks glycogen and starches (complex carbohydrates) into glucose Also referred to as ptyalin Enzyme does not have a lot of functional significance as it only functions in relatively neural environments Since food does not remain for long amounts of time in a neutral environment (as it moves the stomach) the maltase only has a short period of time where it is capable of acting
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o Epithelium of the wall of the mouth are stratified and exfoliated and pass through the digestive tract - Purpose of saliva o Softens food material (moistens the food) o Makes food easier to be swallowed and passed through the upper parts of the digestive tract o Enhances taste of the food Food gustatory and olfactory sensations must be brought into solution in order to be tasted o Starts initial digestive processes (particularly carbohydrates) - When dehydrated, saliva production in the body tends to decrease o Provides an increase sense of thirst Swallowing - Once the food material has been moistened and masticated to some extent, the food is formed into a bolus (a small lump) it is swallowed and passed through the oral cavity into the upper parts of the esophagus - The process of swallowing is referred to as deglutition - The tongue acts as a plunger, pushing the bolus to the rear portion of the mouth - There are specialized receptors at the rear of the mouth and the wall of the pharynx
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This note was uploaded on 10/23/2011 for the course BIOL 2125 taught by Professor Dr.park during the Winter '02 term at A.T. Still University.

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March 5 Lecture - March 5, 2009 The Digestive System The...

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