The Digestive System Functions PDF

The Digestive System Functions ▪ Ingestion—taking in food ▪ Digestion—breaking food into nutrient molecules ▪ Absorption—movement of nutrients into the bloodstream ▪ Defecation—excretes to rid the body of indigestible waste © 2018 Pearson Education, Ltd.  Anatomy of the Di...

The Digestive System Functions ▪ Ingestion—taking in food ▪ Digestion—breaking food into nutrient molecules ▪ Absorption—movement of nutrients into the bloodstream ▪ Defecation—excretes to rid the body of indigestible waste © 2018 Pearson Education, Ltd.  Anatomy of the Digestive System ▪ Two main groups of organs ▪ Alimentary canal (gastrointestinal, or GI, tract)— continuous, coiled, hollow tube ▪ These organs ingest, digest, absorb, defecate ▪ Accessory digestive organs ▪ Include teeth, tongue, and several large digestive organs ▪ Assist digestion in various ways © 2018 Pearson Education, Ltd. Figure 14.1 The human digestive system: Alimentary canal and accessory organs. Mouth (oral cavity) Parotid gland Tongue Sublingual gland Salivary Submandibular glands gland Esophagus Pharynx Stomach Pancreas (Spleen) Liver Gallbladder Transverse colon Duodenum Descending colon Small Jejunum intestine Ascending colon Ileum Large Cecum intestine Sigmoid colon Rectum Appendix Anus Anal canal © 2018 Pearson Education, Ltd.  Organs of the Alimentary Canal ▪ The alimentary canal is a continuous, coiled, hollow tube that runs through the ventral cavity from stomach to anus ▪ Mouth ▪ Pharynx ▪ Esophagus ▪ Stomach ▪ Small intestine ▪ Large intestine ▪ Anus © 2018 Pearson Education, Ltd.  Mouth ▪ Anatomy of the mouth ▪ Mouth (oral cavity)—mucous membrane–lined cavity ▪ 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 © 2018 Pearson Education, Ltd.  Mouth ▪ Anatomy of the mouth (continued) ▪ Vestibule—space between lips externally and teeth and gums internally ▪ Oral cavity proper—area contained by the teeth ▪ Tongue—attached at hyoid bone and styloid processes of the skull, and by the lingual frenulum to the floor of the mouth © 2018 Pearson Education, Ltd.  Mouth ▪ Anatomy of the mouth (continued) ▪ Tonsils ▪ Palatine—located at posterior end of oral cavity ▪ Lingual—located at the base of the tongue © 2018 Pearson Education, Ltd. Figure 14.2a Anatomy of the mouth (oral cavity). Nasopharynx Hard palate Soft palate Oral cavity Uvula Lips (labia) Palatine tonsil Vestibule Lingual tonsil Oropharynx Lingual frenulum Epiglottis Tongue Laryngopharynx Hyoid bone Esophagus Trachea (a) © 2018 Pearson Education, Ltd. Figure 14.2b Anatomy of the mouth (oral cavity). Upper lip Gingivae Hard palate (gums) Soft palate Uvula Palatine tonsil Oropharynx Tongue (b) © 2018 Pearson Education, Ltd.  Mouth ▪ Functions of the mouth ▪ Mastication (chewing) of food ▪ Tongue mixes masticated food with saliva ▪ Tongue initiates swallowing ▪ Taste buds on the tongue allow for taste © 2018 Pearson Education, Ltd. © 2015 Pearson Education, Inc.  Pharynx ▪ Serves as a passageway for foods, fluids, and air ▪ Food passes from the mouth posteriorly into the: ▪ Oropharynx—posterior to oral cavity ▪ Laryngopharynx—below the oropharynx and continuous with the esophagus © 2018 Pearson Education, Ltd.  Pharynx ▪ Food is propelled to the esophagus by two skeletal muscle layers in the pharynx ▪ Longitudinal outer layer ▪ Circular inner layer ▪ Alternating contractions of the muscle layers (peristalsis) propel the food © 2018 Pearson Education, Ltd. Figure 14.2a Anatomy of the mouth (oral cavity). Nasopharynx Hard palate Soft palate Oral cavity Uvula Lips (labia) Palatine tonsil Vestibule Lingual tonsil Oropharynx Lingual frenulum Epiglottis Tongue Laryngopharynx Hyoid bone Esophagus Trachea (a) © 2018 Pearson Education, Ltd.  Esophagus ▪ Anatomy ▪ About 10 inches long ▪ Runs from pharynx to stomach through the diaphragm ▪ Physiology ▪ Conducts food by peristalsis (slow rhythmic squeezing) to the stomach ▪ Passageway for food only (respiratory system branches off after the pharynx) © 2018 Pearson Education, Ltd.  Layers of Tissue in the Alimentary Canal Organs ▪ Summary of the four layers from innermost to outermost, from esophagus to the large intestine (detailed next) 1. Mucosa 2. Submucosa 3. Muscularis externa 4. Serosa © 2018 Pearson Education, Ltd.  Layers of Tissue in the Alimentary Canal Organs 1. Mucosa ▪ Innermost, moist membrane consisting of: ▪ Surface epithelium that is mostly simple columnar epithelium (except for esophagus—stratified squamous epithelium) ▪ Small amount of connective tissue (lamina propria) ▪ Scanty smooth muscle layer ▪ Lines the cavity (known as the lumen) © 2018 Pearson Education, Ltd.  Layers of Tissue in the Alimentary Canal Organs 2. Submucosa ▪ Just beneath the mucosa ▪ Soft connective tissue with blood vessels, nerve endings, mucosa-associated lymphoid tissue, and lymphatic vessels © 2018 Pearson Education, Ltd.  Layers of Tissue in the Alimentary Canal Organs 3. Muscularis externa—smooth muscle ▪ Inner circular layer ▪ Outer longitudinal layer 4. Serosa—outermost layer of the wall; contains fluid-producing cells ▪ Visceral peritoneum—innermost layer that is continuous with the outermost layer ▪ Parietal peritoneum—outermost layer that lines the abdominopelvic cavity by way of the mesentery © 2018 Pearson Education, Ltd. Figure 14.3 Basic structure of the alimentary canal wall. Visceral peritoneum Intrinsic nerve plexuses Myenteric nerve plexus Submucosal nerve plexus Submucosal glands Mucosa Surface epithelium Lamina propria Muscle layer Submucosa Muscularis externa Longitudinal muscle layer Circular muscle layer Serosa (visceral peritoneum) Nerve Gland in Artery Lumen Mesentery mucosa Vein Duct of gland Lymphoid tissue outside alimentary canal © 2018 Pearson Education, Ltd.