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SCAN0105 - 23 The Digestive System Part B Pharynx From the...

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Unformatted text preview: 23 The Digestive System Part B Pharynx From the mouth, the oro- and Iaryngopharynx allow passage of: Food and fluids to the esophagus Air to the trachea Lined with stratified squamous epithelium and mucus glands Has two skeletal muscle layers Inner longitudinal Outer pharyngeal constrictors Esophagus Muscular tube going mm the Iaryngopharynx to the stomach Travels through the mediastinum and pierces the diaphragm Joins the stomach at the cardiac orifice Esophageal Characteristics Esophageal mucosa 0 nonkeratinized stratified squamous epithelium The empty esophagus is folded longitudinally and flattens when food is present Glands secrete mucus as a bolus moves through the esophagus Muscularis changes from skeletal (superiorly) to smooth muscle (inferiorly) Digestive Processes in the Mouth Food is ingested Mechanical digestion begins (chewing) Propulsion is initiated by swallowing Salivary amylase begins chemical breakdown of starch The pharynx and esophagus serve as conduits to pass food from the mouth to the stomach Deglutition (Swallowing) Involves the coordinated activity of the tongue, 'soft palate, pharynx, esophagus and 22 separate muscle groups Buccal phase 9 bolus is forced into the oropharynx Pharyngeal-esophageal phase 0 controlled by the medulla and lower pons All routes except into the digestive tract are sealed off Peristalsis moves food through the pharynx to the esophagus Deglutition (Swallowing) Stomach Chemical breakdown of proteins begins and food is converted to chyme Cardiac region 0 surrounds the cardiac orifice Fundus 0 dome-shaped region beneath the diaphragm Body 0 midportion of the stomach Pyloric region 9 made up of the antrum and canal which terminates at the pylorus The pylorus is continuous with the duodenum through the pyloric sphincter Stomach Greater curvature 0 entire extent of the convex lateral surface Lesser curvature O concave medial surface Lesser omentum 0 runs from the liver to the lesser curvature Greater omentum 0 drapes inferiorly from the greater curvature to the small intestine Stomach Nerve supply 0 sympathetic and parasympathetic fibers of the autonomic nervous system Blood supply 0 celiac trunk, and corresponding veins (part of the hepatic portal system) Stomach Microscopic Anatomy of the Stomach Muscularis 0 has an additional oblique layer that: Allows the stomach to churn, mix, and pummel food physically ...
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