Ch 23 Digestive System

Ch 23 Digestive System - Ch 23: The Digestive System The...

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Ch 23: The Digestive System The function of the digestive system is to provide fuel to the body to use to produce cellular energy. The component parts (anatomy) needed to achieve this can be divided into the organs of the digestive tract itself and the accessory organs of digestion. The processes (physiology) that faciliate this can be divided into 6 subcategories. Organs of the Digestive Tract The digestive tract is basically a tube beginning at the mouth and ending at the anus. Mouth = oral cavity, separated from nasal cavity by hard palate in front, soft palate at rear Contains Tongue Teeth Salivary glands=>accessory organs of digestion Functions = Mastication (Chewing) Swallowing (Deglutition) Pharynx =>behind oral cavity = oropharynx behind epiglottis=laryngopharynx Function = Swallowing Esophagus = a tube connecting the mouth (via pharynx) to the stomach Function = Swallowing (via peristalsis) Stomach = expanded, muscular sac Functions = Storage of food (distention of stomach allows us to eat more at one time) Initiation of protein digestion---->secretion of pepsin Production of chyme by mixing food w/gastric juices Small Intestine = Major Digestive Organ Longest portion of digestive tract ~ 6ft in living person, 1” diameter (Cadavers lose muscle tone, so sm. Intestine is much longer in death) Divided into 3 regions: Duodenum (shortest, attached to stomach) Jejunum (longest, middle) Ileum (attached to large intestine) Functions Completion of digestion (macromolecules to monomers) Site of all absorption of nutrient molecules Accessory organs of digestion associated w/sm. Intestine are Pancreas => pancreatic digestive enzymes secreted into sm. Intestine Liver => bile secreted into sm. Intestine aids in fat digestion
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Large Intestine = colon Shorter, but larger in diameter than small intestine Divided into 5 regions Ascending colon Transverse colon Descending colon Rectum Functions = Digestive processes => harvest vitamins produced by resident bacteria; reabsorption water Main function is production of feces and their excretion (defecation) Histological Organization Mucosa Submucosa Muscularis Externa Serosa (Adventitia) Mucosa = innermost layer Epithelium=> lining Simple columnar epithelium dominates the rest of the tract Lamina propria = loose connective tissue, contains glands & submucosal plexus Muscularis mucosa = muscles controlling shape of epithelial lining Submucosa Loose connective tissue Contains glands secreting onto mucosal epithelium Muscularis externa => found from esophagus to anus Consists of 2 layers of smooth muscle EXCEPT in stomach = 3 layers Outer layer = longitudinal
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Ch 23 Digestive System - Ch 23: The Digestive System The...

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