Week 1 Digestion - Digestion This section was probably...

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Digestion This section was probably covered in biology and probably in high school. There are a just a few key points that must be covered to make an understanding of other sections more complete. Digestion is really about getting nutrients from the food and into the body where they can be used for energy or other purposes. In most cases for something to be absorbed into the blood stream it must exist in the simplest chemical form. If it is two sugars hooked together they can only be absorbed if they are separated into two individual sugars. The body seems to go on the principle that if it cannot convert it into the simplest form it may either be toxic or of no use. This is especially true for substances that are water soluble. For those that are fat soluble a mechanism exists for absorption of slightly larger molecules. The processing of food takes place in four stages Ingestion Digestion Absorption Elimination Ingestion The act of eating. This is only the first of four main stages of food processing. Very little true digestion occurs at this stage. Some digestion of starch by amylases Break food down as much as possible to speed subsequent steps Digestion Process that beaks down food into molecules small enough to absorb. Break polymers into monomers that are easier to absorb and that can be used to synthesize new polymers required by the organism. Absorption Cells that line tract take up nutrients Nutrients move to cells where they are Incorporated into the cells Converted to energy which may be used immediately or stored until needed Elimination In the last stage of food processing, elimination, undigested waste pass out of the digestive tract. Components of the Human Digestive System Mouth Oral cavity Tongue Pharynx Salivary Glands Esophagus Stomach Liver Gall Bladder Pancreas Small Intestine Large Intestine Rectum Anus Oral Cavity Food enters the mouth and is reduced in size by teeth and tongue. Salivary glands secrete saliva which o Lubricates o Buffers o Contains antimicrobial substances o Contains amylase to digest starch The main purpose of the action in the mouth is to decrease the size of the food to make it easier to digest in subsequent stages. Saliva contains an enzyme called lysozyme that has some bactericidal action. Saliva also lubricates the food to make it easier to swallow. There is a little of the enzyme amylase produced in the mouth. This will start digesting starch and converting into sugar. You can
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detect the action of this enzyme by placing a thin slice of cooked potato on your tongue and holding it there for a couple of minutes. In time you will start to detect sweetness Swallowing Food passes to pharynx that contains both trachea and esophagus Epiglottis prevents food from entering trachea Food passes through esophagus into the stomach Food moves through the digestive system by a process known as peristalsis. This is a wavelike muscular squeezing that moves food
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This note was uploaded on 04/23/2008 for the course FD SC&TE 201D taught by Professor Mangino during the Winter '08 term at Ohio State.

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Week 1 Digestion - Digestion This section was probably...

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