Digestive System Lecture Slides PDF

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Digestive System Part A 23 Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson E...

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Digestive System Part A 23 Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Digestive System: Overview ▪ The alimentary canal or gastrointestinal (GI) tract digests and absorbs food ▪ Alimentary canal – mouth, pharynx, esophagus, stomach, small intestine, and large intestine ▪ Accessory digestive organs – teeth, tongue, gallbladder, salivary glands, liver, and pancreas Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Digestive System: Overview Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23.1  Digestive Process ▪ The GI tract is a “disassembly” line ▪ Nutrients become more available to the body in each step ▪ There are six essential activities: ▪ Ingestion, propulsion, and mechanical digestion ▪ Chemical digestion, absorption, and defecation Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Digestive Process Figure 23.2 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Gastrointestinal Tract Activities ▪ Ingestion – taking food into the digestive tract ▪ Propulsion – swallowing and peristalsis ▪ Peristalsis – waves of contraction and relaxation of muscles in the organ walls ▪ Mechanical digestion – chewing, mixing, and churning food Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Peristalsis and Segmentation Figure 23.3 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Gastrointestinal Tract Activities ▪ Chemical digestion – catabolic breakdown of food ▪ Absorption – movement of nutrients from the GI tract to the blood or lymph ▪ Defecation – elimination of indigestible solid wastes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Peritoneum and Peritoneal Cavity ▪ Peritoneum – serous membrane of the abdominal cavity ▪ Visceral – covers external surface of most digestive organs ▪ Parietal – lines the body wall ▪ Peritoneal cavity ▪ Lubricates digestive organs ▪ Allows them to slide across one another Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Peritoneum and Peritoneal Cavity Figure 23.5a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Peritoneum and Peritoneal Cavity ▪ Mesentery – double layer of peritoneum that provides: ▪ Vascular and nerve supplies to the viscera ▪ A means to hold digestive organs in place and store fat Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Blood Supply: Splanchnic Circulation ▪ Arteries and the organs they serve include ▪ The hepatic, splenic, and left gastric: spleen, liver, and stomach ▪ Inferior and superior mesenteric: small and large intestines ▪ Hepatic portal circulation: ▪ Collects nutrient-rich venous blood from the digestive viscera ▪ Delivers this blood to the liver for metabolic processing and storage Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Histology of the Alimentary Canal ▪ From esophagus to the anal canal the walls of the GI tract have the same four tunics ▪ From the lumen outward they are the mucosa, submucosa, muscularis externa, and serosa ▪ Each tunic has a predominant tissue type and a specific digestive function Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Histology of the Alimentary Canal Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23.6  Mucosa ▪ Moist epithelial layer that lines the lumen of the alimentary canal ▪ Its three major functions are: ▪ Secretion of mucus ▪ Absorption of the end products of digestion ▪ Protection against infectious disease ▪ Consists of three layers: a lining epithelium, lamina propria, and muscularis mucosae Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Mucosa: Epithelial Lining ▪ Consists of simple columnar epithelium and mucus- secreting goblet cells ▪ The mucus secretions: ▪ Protect digestive organs from digesting themselves ▪ Ease food along the tract ▪ Stomach and small intestine mucosa contain: ▪ Enzyme-secreting cells Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Mucosa: Lamina Propria and Muscularis Mucosae ▪ Lamina Propria ▪ Loose areolar and reticular connective tissue ▪ Nourishes the epithelium and absorbs nutrients ▪ Muscularis mucosae – smooth muscle cells that produce local movements of mucosa Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Mucosa: Other Sublayers ▪ Submucosa – dense connective tissue containing elastic fibers, blood and lymphatic vessels, lymph nodes, and nerves ▪ Muscularis externa – responsible for segmentation and peristalsis ▪ Serosa – the protective visceral peritoneum ▪ Replaced by the fibrous adventitia in the esophagus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Mouth ▪ Oral or buccal cavity: ▪ Is bounded by lips, cheeks, palate, and tongue ▪ Has the oral orifice as its anterior opening ▪ Is continuous with the oropharynx posteriorly ▪ To withstand abrasions: ▪ The mouth is lined with stratified squamous epithelium ▪ The gums, hard palate, and dorsum of the tongue are slightly keratinized Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Anatomy of the Oral Cavity: Mouth Figure 23.7a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Oral Cavity and Pharynx: Anterior View Figure 23.7b Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Palate ▪ Hard palate – underlain by palatine bones and palatine processes of the maxillae ▪ Assists the tongue in chewing Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Palate ▪ Soft palate – mobile fold formed mostly of skeletal muscle ▪ Closes off the nasopharynx during swallowing ▪ Uvula projects downward from its free edge Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Tongue ▪ Occupies the floor of the mouth and fills the oral cavity when mouth is closed ▪ Functions include: ▪ Gripping and repositioning food during chewing ▪ Mixing food with saliva and forming the bolus ▪ Initiation of swallowing, and speech Note: Lingual frenulum secures the tongue to the floor of the mouth Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Tongue ▪ Superior surface bears three types of papillae ▪ Filiform – give the tongue roughness and provide friction ▪ Fungiform – scattered widely over the tongue and give it a reddish hue ▪ Circumvallate – V-shaped row in back of tongue Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Tongue Figure 23.8 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Salivary Glands ▪ Produce and secrete saliva that: ▪ Three pairs of extrinsic glands – parotid, submandibular, and sublingual Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Salivary Glands ▪ Parotid – lies anterior to the ear between the masseter muscle and skin ▪ Parotid duct – opens into the vestibule next to the second upper molar ▪ Submandibular – lies along the medial aspect of the mandibular body ▪ Sublingual – lies anterior to the submandibular gland under the tongue Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Salivary Glands Figure 23.9a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Permanent Teeth Figure 23.10.2 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Classification of Teeth ▪ Teeth are classified according to their shape and function ▪ Incisors – chisel-shaped teeth adapted for cutting or nipping ▪ Canines – conical or fanglike teeth that tear or pierce ▪ Premolars (bicuspids) and molars – have broad crowns with rounded tips and are best suited for grinding or crushing During chewing, upper and lower molars lock together generating crushing force Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Tooth Structure Figure 23.11 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings