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Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 14 The Digestive System Anatomy Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Organs of the Digestive System Two main groups Alimentary canal (Gastrointestinal (GI) tract)– continuous, coiled, hollow, muscular tube that ingests, digests, absorbs, and defecates and is open on both ends; about 30 feet long Accessory digestive organs – assist the process of digestive breakdown in various ways Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.2a Organs of the Digestive System (Know this!) Figure 14.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.2b Organs of the Alimentary Canal Mouth Pharynx Esophagus Stomach Small intestine Large intestine Anus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.3 Mouth (Oral Cavity) Anatomy Lips (labia) – protect the anterior opening Cheeks – form the lateral walls Hard palate – forms the anterior roof Soft palate – forms the posterior roof Uvula – fleshy projection of the soft palate Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.2a Slide 14.4 Mouth (Oral Cavity) Anatomy Vestibule – space between lips and cheeks externally and teeth and gums internally Oral cavity proper – area contained by the teeth Tongue –muscular; occupies floor of mouth; attached to floor of mouth by the lingual frenulum Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.2a Slide 14.5 Mouth (Oral Cavity) Anatomy Slide 14.5 Children born with an extremely short frenulum are referred to as “tongue-tied” because distorted speech results when tongue movement is restricted. This can be corrected surgically by cutting the frenulum. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mouth (Oral Cavity) Anatomy Tonsils: masses of lymphatic tissue Palatine tonsils Lingual tonsil-at base of tongue Inflamed tonsils make swallowing difficult and painful Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.6 Pharynx Anatomy Nasopharynx – not part of the digestive system Oropharynx – posterior to oral cavity Laryngopharynx – below the oropharynx and connected to the esophagus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.2a Slide 14.8 Layers of Alimentary Canal Organs Figure 14.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.13 Layers of Alimentary Canal Organs The walls of the alimentary canal organs from the esophagus to the large intestine are made up of the same four basic tissue layers (tunics): 1. Mucosa Innermost layer Moist membrane Surface epithelium Small amount of connective tissue (lamina propria) Small smooth muscle layer Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.11a Layers of Alimentary Canal Organs 2. Submucosa Just beneath the mucosa Soft connective tissue with blood vessels, nerve endings, and lymphatics Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.11b Layers of Alimentary Canal Organs 3. Muscularis externa – smooth muscle Inner circular layer Outer longitudinal layer 4. Serosa Outermost layer – visceral peritoneum, which is continuous with parietal peritoneum by way of the mesentery Layer of serous fluid-producing cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.12 Layers of Alimentary Canal Organs Figure 14.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.13 Esophagus (Gullet) Runs from pharynx to stomach through the diaphragm About 10 inches long Conducts food by peristalsis (slow rhythmic squeezing) Passageway for food only (respiratory system branches off after the pharynx) No serous lining on the esophagus Stomach Anatomy C-shaped Located on the left side of the abdominal cavity Can hold about 1 gallon of food when full Food enters at the cardioesophageal sphincter Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.15a Stomach Anatomy Regions of the stomach Cardiac region – near the heart Fundus – expanded part lateral to cardiac region Body -- midportion Pylorus – funnel-shaped terminal end Food empties into the small intestine at the pyloric sphincter Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.15b Stomach Anatomy Antrum Figure 14.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.17 Stomach Anatomy Rugae – internal folds of the mucosa External regions Lesser curvature: concave medial surface Greater curvature: convex lateral surface Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.16a Specialized Mucosa of the Stomach Simple columnar epithelium Mucous neck cells – produce a sticky alkaline mucus (glycoprotein) protects the stomach wall from being damaged Gastric glands in gastric pits – secrete gastric juice Chief cells – produce protein-digesting enzymes (pepsinogens) Parietal cells – produce hydrochloric acid that makes the stomach contents acidic and activates the enzymes (located only in the fundus and the body) Endocrine cells – produce gastrin Structure of the Stomach Mucosa Stomach mucosa looks like moist velvet to the naked eye. Figure 14.4b, c Stomach Anatomy Layers of peritoneum attached to the stomach Lesser omentum – attaches the liver to the lesser curvature Greater omentum – attaches the greater curvature to the posterior body wall Contains fat to insulate, cushion, and protect abdominal organs Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.16b Small Intestine The body’s major digestive organ Longest section of the alimentary tube, with an average length of 6-13 feet Site of nutrient absorption into the blood Muscular tube extending form the pyloric sphincter to the ileocecal valve Suspended from the posterior abdominal wall by the mesentery Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.21 Subdivisions of the Small Intestine Duodenum Attached to the stomach Curves around the head of the pancreas (retroperitoneal) Pyloric sphincter controls food movement into the duodenum Jejunum Attaches anteriorly to the duodenum Ileum Extends from jejunum to large intestine Folds of the Small Intestine Called circular folds or plicae circulares Deep folds of the mucosa and submucosa Do not disappear when filled with food The submucosa has Peyer’s patches (collections of lymphatic tissue that prevent bacteria from entering the bloodstream) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.27 Villi of the Small Intestine Fingerlike structures formed by the mucosa Give the small intestine more surface area for absorption Figure 14.7a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.24 Microvilli of the Small Intestine Small projections of the plasma membrane of the mucosa cells Also known as the brush border Found on absorptive cells Figure 14.7c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.25 Structures Involved in Absorption of Nutrients Absorptive cells Blood capillaries Lacteals (specialized lymphatic capillaries) Figure 14.7b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.26 Large Intestine Larger in diameter, but shorter in length than the small intestine About 5 feet Extends from ileocecal valve to anus Frames the internal abdomen Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.28 Large Intestine Figure 14.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.28 Structures of the Large Intestine Cecum – saclike first part of the large intestine Appendix Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis) Hangs from the cecum Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.30a Structures of the Large Intestine Colon Ascending colon: travels up the right side of the abdominal cavity and makes a turn at the right colic flexure Transverse colon: leads transversely to left colic flexure Descending colon: descends down left side Sigmoid colon: S-shaped; in pelvis Rectum Anal Canal – external body opening; has an external voluntary sphincter and an internal involuntary sphincter; ends in anus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.30b Coverings of the Digestive System Peritoneum (AKA - Mesentery) Two serous tissue layers with fluid between the layers Parietal peritoneum – in contact with the abdominal wall Visceral peritoneum – in contact with the digestive organs peritoneum Mesenteries Accessory Digestive Organs Notes Salivary glands Teeth Pancreas Liver Gallbladder Slide 14.32 Salivary Glands Saliva-producing glands Three pairs Parotid glands – located anterior to ears Mumps (viral disease that spreads through saliva) is an inflammation of the parotid glands (child looks like a “hampster with food in its cheeks”) Submandibular glands Sublingual glands Slide 14.33 Slide 14.33 Salivary Glands Mumps Teeth The role is to masticate (chew) food, tearing and grinding the food into smaller fragments Humans have two sets of teeth Deciduous (baby or milk) teeth Begin to erupt around six months 20 teeth are fully formed by age two Lower central incisors appear first Slide 14.35a Teeth Permanent teeth Replace deciduous teeth between the ages of 6 and 12 As permanent teeth enlarge and develop, the roots of deciduous teeth are reabsorbed By the end of adolescence, all the permanent teeth but the third molars (“wisdom teeth”) have erupted (making a total of 28 teeth) Third molars erupt between the ages of 17 and 25 A full set is 32 teeth, but some people do not have third molars Slide 14.35b Impacted Teeth Slide 14.35b Occurs when teeth remain embedded in jawbone Exert pressure, cause pain, and must be removed surgically Third molars are the most commonly impacted teeth Classification of Teeth Incisors: chisel-shaped, adapted for cutting Canines (cuspids): fanglike, “eyeteeth,” for tearing or piercing Premolars (bicuspids): broad crowns with rounded cusps for grinding Molars: broad crowns with rounded cusps for grinding Classification of Teeth Figure 14.9 Slide 14.36b Regions of a Tooth Crown – exposed part (above gingiva) Outer enamel Dentin-forms bulk of tooth Pulp cavity-has blood vessels and nerve fibers; supplies nutrients to the tooth and provides for tooth sensations Figure 14.10 Slide 14.37a Regions of a Tooth Neck Region in contact with the gum Connects crown to root Figure 14.10 Slide 14.37a Regions of a Tooth Root Embedded in jawbone Covered with cementum Periodontal membrane (ligament) attaches tooth to the jaw bone Root canal carrying blood vessels and nerves Figure 14.10 Slide 14.37b Slide 14.38 Pancreas (all – flesh) Soft, pink, triangular gland; retroperitoneal Produces a wide spectrum of digestive enzymes that break down all categories of food Enzymes are secreted into the duodenum Alkaline fluid introduced with enzymes neutralizes acidic chyme Endocrine products of pancreas Insulin (Beta Cells) Glucagon (Alpha Cells) Slide 14.38 Liver Largest gland in the body Located on the right side of the body under the diaphragm Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament Connected to the gallbladder via the common hepatic duct Produces bile, which emulsifies fats Slide 14.39 Gall Bladder Small, thin-walled green sac found in hollow fossa of liver Stores bile from the liver by way of the cystic duct Bile is introduced into the duodenum in the presence of fatty food Gallstones (when cholesterol in bile crystallizes because it is stored too long) can cause blockages. This backs up the liver, causing bile pigments to enter the bloodstream. Tissues become jaundiced. Hepatitis or cirrhosis (inflammation of liver) can also cause jaundice Slide 14.41 Slide 14.38