FSU BSC 2086 - The Digestive System
Type Lecture Slides
Pages 88

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BSC 2086 01 Anatomy and Physiology II Spring 2013 17 18 The Digestive System 2012 Pearson Education Inc An Introduction to the Digestive System Learning Outcomes 24 3 Describe the structure and functions of the 24 4 Describe the structure and functions of the pharynx esophagus 24 5 Describe the anatomy of the stomach including its histological features and discuss its roles in digestion and absorption 24 6 Describe the anatomical and histological characteristics of the small intestine explain the functions and regulation of intestinal secretions and describe the structure functions and regulation of the accessory digestive organs 2012 Pearson Education Inc An Introduction to the Digestive System Learning Outcomes 24 7 Describe the gross and histological structure of the large intestine including its regional specializations and role in nutrient absorption 24 8 List the nutrients required by the body describe the chemical events responsible for the digestion of organic nutrients and describe the mechanisms involved in the absorption of organic and inorganic nutrients 24 9 Summarize the effects of aging on the digestive system 2012 Pearson Education Inc 24 3 The Pharynx The Pharynx Throat A common passageway for solid food liquids and air Regions of the pharynx nasopharynx oropharynx laryngopharynx The Esophagus A hollow muscular tube About 25 cm 10 in long and 2 cm 0 80 in wide Conveys solid food and liquids to the stomach Enters abdominopelvic cavity through the esophageal hiatus 2012 Pearson Education Inc 24 4 The Esophagus Resting Muscle Tone In the circular muscle layer in the superior 3 cm 1 2 in of esophagus prevents air from entering upper esophageal sphincter Inferior end of esophagus lower esophageal sphincter normally remains in a state of active contraction Prevents backflow from stomach into esophagus 2012 Pearson Education Inc Figure 24 10a The Esophagus Muscularis mucosae Mucosa Submucosa Muscularis externa Adventitia 2012 Pearson Education Inc A transverse section through an empty esophagus 24 4 The Esophagus Swallowing Also called deglutition Can be initiated voluntarily Proceeds automatically Is divided into three phases 1 Buccal phase tongue pushes bolus into oropharynx soft palate elevates and seals nasopharynx voluntary 2 Pharyngeal phase epiglottis covers glottis to channel bolus into esophagus 3 Esophageal phase peristaltic contractions push bolus into stomach 2012 Pearson Education Inc Figure 24 11 The Swallowing Process Buccal Phase Trachea Pharyngeal Phase Soft palate Bolus Epiglottis Esophagus Tongue Bolus The buccal phase begins with the compression of the bolus against the hard palate Subsequent retraction of the tongue then forces the bolus into the oropharynx and assists in the elevation of the soft palate thereby sealing off the nasopharynx Once the bolus enters the oropharynx reflex responses begin and the bolus is moved toward the stomach The pharyngeal phase begins as the bolus comes into contact with the palatoglossal and palatopharyngeal arches and the posterior pharyngeal wall Elevation of the larynx and folding of the epiglottis direct the bolus past the closed glottis At the same time the uvula and soft palate block passage back to the nasopharynx 2012 Pearson Education Inc Figure 24 11 The Swallowing Process Esophageal Phase The esophageal phase begins as the contraction of pharyngeal muscles forces the bolus through the entrance to the esophagus Once in the esophagus the bolus is pushed toward the stomach by a peristaltic wave Peristalsis Trachea Bolus Enters Stomach Thoracic cavity The approach of the bolus triggers the opening of the lower esophageal sphincter The bolus then continues into the stomach Lower esophageal sphincter Stomach 2012 Pearson Education Inc 24 5 The Stomach Major Functions of the Stomach 1 Storage of ingested food 2 Mechanical breakdown of ingested food 3 Disruption of chemical bonds in food material by acid and enzymes 4 Production of intrinsic factor a glycoprotein required for absorption of vitamin B12 required for normal erytropoiesis in small intestine 2012 Pearson Education Inc 24 5 The Stomach Anatomy of the Stomach The stomach is shaped like an expanded J Short lesser curvature forms medial surface Long greater curvature forms lateral surface Anterior and posterior surfaces are smoothly rounded Shape and size vary from individual to individual and from one meal to the next Four regions of stomach Cardia Fundus Body largest part where mixing of food and secretions occur Pylorus 2012 Pearson Education Inc Figure 24 12a The Stomach Esophagus Right lobe of liver Vagus nerve N X Lesser omentum Lesser curvature Duyodenum Pyloric sphincter Pylorus Left gastroepiploic vessels 2012 Pearson Education Inc Diaphragm Fundus Cardia Spleen Greater curvature with greater omentum attached Greater omentum Body The position and external appearance of the stomach showing superficial landmarks Figure 24 12b The Stomach Esophagus Cardia Longitudinal muscle layer Circular muscle layer Lesser curvature medial surface Pyloric sphincter Duodenum Pyloric canal Pylorus Pyloric antrum 2012 Pearson Education Inc Fundus Anterior surface Left gastroepiploic vessels Body Oblique muscle layer overlying mucosa Rugae Greater curvature lateral surface The structure of the stomach wall 24 5 The Stomach Smooth Muscle of Stomach Muscularis mucosae and muscularis externa Contain extra layers of smooth muscle cells Oblique layer in addition to circular and longitudinal layers Found in muscularis externa Strengthens stomach wall and assist in mixing of food with stomach secretions to form chyme 2012 Pearson Education Inc 24 5 The Stomach Histology of the Stomach Simple columnar epithelium lines all portions of stomach Epithelium is a secretory sheet Produces mucus that covers interior surface of stomach Gastric pits shallow depressions that open onto the gastric surface Mucous cells at the base or neck of each gastric pit actively divide replacing superficial cells Gastritis inflammation of mucosa caused by alcohol aspirin consumption emotional physical stress smoking bacterial infection ingestion of strong acids bases Can lead to gastric or peptic ulcers 2012 Pearson Education Inc 24 5 The Stomach Gastric Glands In fundus and body of stomach Extend deep into underlying lamina propria Each gastric pit communicates with several gastric glands Parietal cells Secrete intrinsic factor needed for the absorption of vitamin B12 and hydrochloric acid HCl


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FSU BSC 2086 - The Digestive System

Type: Lecture Slides
Pages: 88
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