Digestive

• The course module also includes the identification of the organs of the alimentary and accessory digestive organs, describing the general function of each.
• The course module explains how the accessory organs contribute to the digestive processes.
• The organs of the alimentary canal include the mouth, pharynx, esophagus, stomach, small intestine, and large intestine, and the anus.
• Accessory digestive organs include teeth, tongue, and several large digestive organs that assist digestion in various ways.
• Ion refers to the process of breaking food into nutrient molecules.
• Tonsils are located in the posterior end of the oral cavity.
• The tongue is attached at the hyoid bone and styloid processes of the skull, and by the lingual frenulum to the floor of the mouth.
• The mouth, or oral cavity, is a mucous membrane-lined cavity with lips (labia) that protect the anterior opening, cheeks that form the lateral walls, a hard palate that forms the anterior roof, a soft palate that forms the posterior roof, a uvula that is a fleshy projection of the soft palate, a vestibule that is the space between lips externally and teeth and gums internally, and an oral cavity proper that is the area contained by the teeth.
• Lingual tonsils are located at the base of the tongue.
• Absorption is the movement of nutrients into the bloodstream.
• Defecation is the process of excreting to rid the body of indigestible waste.
• Palatine tonsils are located at the posterior end of the oral cavity.
• The alimentary canal, or GI tract, is a continuous, coiled, hollow tube that ingests, digests, absorbs, and defecates.
• The root canal is where the pulp cavity extends into the root.
• The cement covers the outer surface and attaches the tooth to the periodontal membrane (ligament), the periodontal membrane holds the tooth in place in the bony jaw, and the neck is a connector between the crown and root.
• The Large Intestine is a section of the cecum that shows the ileocecal valve.
• The crown is the exposed part of the tooth above the gingiva (gum), the enamel covers the crown, the dentin is found deep to the enamel and forms the bulk of the tooth, surrounds the pulp cavity, and the pulp cavity contains connective tissue, blood vessels, and nerve fibers (pulp).
• Deciduous and Permanent Teeth are classified according to shape and function as Incisors for cutting, Canines (eyeteeth) for tearing or piercing, Premolars (bicuspids) for grinding, and Molars for grinding.
• The anal canal ends at the anus, which is the opening of the large intestine.
• The large intestine is larger in diameter, but shorter in length at 1.5 m, than the small intestine and extends from the ileocecal valve to the anus.
• The large intestine delivers indigestible food residues to the body’s exterior, goblet cells produce alkaline mucus to lubricate the passage of feces, and the muscularis externa layer is reduced to three bands of muscle, called teniae coli, which cause the wall to pucker into haustra (pocketlike sacs).
• A full set of permanent teeth is 32 teeth (with the wisdom teeth).
• The external anal sphincter is formed by skeletal muscle and is voluntary, while the internal anal sphincter is formed by smooth muscle and is involuntary.
• The cecum is the saclike first part of the large intestine, the appendix accumulates lymphoid tissue that sometimes becomes inflamed (appendicitis), and the colon, rectum, and anal canal are located in the pelvis.
• The large intestine is subdivided into the cecum, appendix, colon, rectum, and anal canal.
• These sphincters are normally closed except during defecation.
• The duodenum of the small intestine and related organs increase surface area for food absorption, decrease in number toward the end of the small intestine, and contain villi, microvilli, circular folds, Peyer’s patches, and collections of lymphatic tissue.
• Humans have two sets of teeth during a lifetime: deciduous (baby or milk) teeth and permanent teeth, which replace deciduous teeth between ages 6 and 12.
• The layers of tissue in the alimentary canal include the mucosa, submucosa, muscularis externa, and serosa.
• The stomach is a C-shaped organ located on the left side of the abdominal cavity, where food enters at the cardioesophageal sphincter from the esophagus and empties into the small intestine at the pyloric sphincter.
• The esophagus conducts food by peristalsis (slow rhythmic squeezing) to the stomach and is a passageway for food only, with the respiratory system branches off after the pharynx.
• The pharynx serves as a passageway for foods, fluids, and air, with food passing from the mouth posteriorly into the Oropharynx, Laryngopharynx, and Esophagus.
• The alimentary canal wall contains two intrinsic nerve plexuses that are part of the autonomic nervous system: the submucosal nerve plexus and the myenteric nerve plexus, which regulate mobility and secretory activity of the GI tract organs.
• The esophagus is about 10 inches long and runs from the pharynx to the stomach through the diaphragm.
• The stomach has regions: the cardia, fundus, body, and pyloric region.
• The functions of the mouth include mastication (chewing) of food, mixing masticated food with saliva, initiating swallowing, and allowing for taste.
• Swallowing involves the functions of the mouth, pharynx, and esophagus.
• Propulsion is the movement of foods from one region of the digestive system to another, including peristalsis and segmentation.
• Saliva is a mixture of mucus and serous fluids that helps to moisten and bind food together into a mass called a bolus.
• Saliva contains enzymes such as salivary amylase, which begins starch digestion, and lysozymes and antibodies, which inhibit bacteria.