DIGESTIVE SYSTEM III. Pharynx - common to resp. & digestive systems. Connects oral cavityto esophagus & nasal cavity to larynx.Function: voluntary propelling food/drink from mouth to esophagusA. 3 parts1. Nasopharynx – not part of the digestive system2. Oropharynx – air and food3. Laryngopharynx – air and foodB. Histology1. Tunica Mucosa: contains non-keratinized stratified squamous2. Tunica Submucosa: C.T.3. Tunica Muscularis: composed of 3 bands of skeletal muscle (constrictors)a. superior- nasopharynx b. middle- oropharynxc. inferior- laryngopharynx 4. Tunica Adventitia: C.T.II. EsophagusA. Connects pharynx to stomachB. Passes through diaphragm at esophageal hiatusC. Ends at stomach; its Muscularis layer forms the gastroesophageal (cardiac) sphincterD. Histology 1. Mucosa – non-keratinized stratified squamous epithelium 2. Submucosa - contains mucous glands 3. Muscularis - 3 sections a. Upper 1/3 = skeletal b. Middle 1/3 = skeletal and smooth c. Lower 1/3 = smooth4. Adventitia - c.t. E. Function: voluntary and involuntary movement of food to stomachIII. StomachA. 4 regions: cardiac, fundus, body, & pylorus. B. Histology 1. Mucosa – has Gastric Pits which open up into Gastric Glands. The Gastric Glands are composed primarily of: a. Simple columnar epi. – 3 cell types i. Mucous neck cells – protection ii. Parietal cells – secrete HCl iii. Chief cells – secrete pepsinogen (inactive enzyme that is activated to pepsin by HCl; for protein digestion) 2. Submucosa - c.t. 3. Muscularis – 3 layers of smooth muscle; longitudinal, oblique & circular 4. Serosa – c.t. + simple squamousC. Has two peritoneal membranes associated with it; Greater Omentum & Lesser OmentumIV. Small IntestineA. 3 regions: duodenum, jejunum, & ileum. B. Histology 1. Mucosa has finger-like folds = Villi a. Epithelium – Simple Columnar; microvilli for secretion & absorption; goblet cells for mucusb. Lamina propria – contains lacteals (lymphatic capillaries) c. Muscularis mucosae Between villi = intestinal glands (crypts of Lieberkuhn) 2. Submucosa is thrown up into folds = Plicae Circularis. ContainsPyer’s patch (group of WBC’s) 3. Muscularis - 2 layers of smooth muscle; outer longitudinal layerand inner circular layer 4. Serosa – connective tissue underlying simple squamous C. Function 1. Duodenum: most chemical digestion occurs here because; a. The duodenal cells of the intestinal glands make enzymesto break down food b. receives bile from the gall bladder c. It receives enzymes from the pancreas for the breakdown of foodBILIARY APPARATUSCommon Bile Duct Pancreatic (from gall bladder Duct and liver) Hepatopancreatic ampulla (surrounded by the hepatopancreatic sphincter) Duodenal papilla(volcano shaped) Duodenum 2. Jejunum – absorption occurs here 3. Ileum - very little absorption Most Chemical Digestion occurs in the duodenum and digestionis completed in Small Intestine. The small intestine ends at the Ileocecal valve. Which of the following contains 3 layers of smooth muscle in its muscularis?a. Stomachb. Small intestinec. Large intestined. Esophaguse.
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