Slide 1IntroductionSlide 3GI tract/Accessory Digestive OrgansDigestive System FunctionsPeristalsis and SegmentationPeristalsis and SegmentationPeritoneumPeritoneumMesenteriesPeritoneumMesenteriesMesenteriesOral cavity/Cheeks and LipsPalateCheeks, Lips, and PalateSlide 17Salivary GlandsSalivary GlandsTeethPermanent TeethSlide 22PharynxSlide 24Esophagus/EsophagealsphinctersSlide 26Phases of SwallowingStomachStructure of StomachGastric Folds Structure of StomachSmall IntestineSlide 32Duodenum/jejunum/ileumHistology of the Small IntestineHistology of the Small IntestineSmall IntestineLarge IntestineCecum /sigmoid colon/rectumAscending/transverse/descending colonLarge IntestineAccessory Digestive OrgansLiverLiverGall Bladder/pancreasPancreasDigestive SystemIntroductionThe digestive system includes organs that:ingest the foodtransport the ingested materialdigest the material into smaller usable componentsabsorb the necessary digested nutrients into the bloodstreamexpel waste products from the bodyThe digestive system is composed of two separate categories of organs:1. Digestive organscollectively make up the gastrointestinal (GI) tract, also called the digestive tract or the alimentary canalForm cont. tube2. Accessory digestive organs2. Not part of GI tubeFigure 26.1GI tract/Accessory Digestive OrgansThe GI tract organs are as follows:oral cavitypharynxesophagusstomachsmall intestinelarge intestineThe accessory digestive organs are not part of the long GI tube, but often develop as outgrowths of that tube. They are as follows: teeth tongue salivary glands liver gall bladder pancreasDigestive System FunctionsIngestion-intro of solid/liquid materials into oral cavityDigestion-breakdown of foodPropulsion-movement of food through GI tractSecretion-releases mucin, fluids (acid, bile, digestive enzymesAbsorptionElimination of wastesPeristalsis and SegmentationPropulsion of food along the GI tube involves two types of movement:peristalsissegmentationPeristalsis is the ripple-like wave of muscular contraction that forces material to move further along the GI tract.Segmentation is the churning and mixing of material helping to disperse the material and mix it and combine it with digestive organ secretions.Peristalsis and SegmentationPeritoneumAbdominopelvic cavity is covered with moist serous membranes: parietal peritoneum—lines the inside surface of the body wall visceral peritoneum—covers the surface of internal organs within the cavity Function: Allows organs to move over each other without frictionAllows digestive movementsContains leukocytes (whote blood cells)and antibodies that prevent infectionPeritoneumFigure 26.7MesenteriesFolds of peritoneum that support and stabilize intraperitoneal GI tract organsBlood vessels, lymphatic vessels, and nerves are sandwiched between the two folds and supply the digestive organsSeveral different types of mesenteriesThe greater omentum extends inferiorly like an apron from the greater curvature of the stomach and covers most of the abdominal organs.The lesser omentum connects the lesser curvature of the stomach and the proximal end of the duodenum to the liver.The mesentery proper suspends most of the small intestines from the posterior abdominal wall.The mesocolon is a peritoneal fold that attaches parts of the large intestine to the posterior abdominal wall.PeritoneumFigure 26.7MesenteriesFigure 26.8MesenteriesFigure 26.8Oral cavity/Cheeks and LipsContains the following structural features:cheeks, lips, and palatetonguesalivary glandsteethCheeks form the lateral wall of the oral cavity and are comprised mainly of the buccinator muscles.The cheeks end anteriorly as the lips.FORMED LARGLY by orbicularis oris muscleThe gingivae (gums) cover the alveolar processes of the teeth.The internal surface of the upper and lower lips are attached to the gingivae by a thin, midline mucosa fold called the labial frenulum.PalateThe palate forms the roof of the oral cavity.The anterior two-thirds of the palate is called the hard palate because it is comprised of bone. The posterior one-third of the palate is soft and muscular and is called the soft palate.Extending from the soft palate posteriorly is the uvula, which elevates during swallowing and closes off the posterior entrance to the nasopharynx.Cheeks, Lips, and PalateFigure 26.3Salivary GlandsSalivary glands produce and secrete saliva into the oral cavity.Saliva serves the following functions:moistens ingested materials to become a slick bolusmoistens, cleanses, and lubricates the structures of the oral cavitychemical digestion of ingested materialsantibacterial actiondissolves materials so that taste receptors on the tongue can be stimulatedThree pairs of salivary glands are located external to the oral cavity: parotid glands (anterior to ear) submandibular glands (lower jaw region) sublingual glands (below the tongue)Salivary GlandsTeethFigure 26.5Permanent TeethTwo sets of teeth develop and erupt in a normal lifetime: deciduous teeth—erupt between 6–30 months, 20 in number, and are often called milk teeth permanent teeth—replace the deciduous teeth and are 32 in numberIncisors—most anteriorly placed, shaped like chisels, and have a single rootCanines—posterolateral to the incisors, pointed tips for puncturing and tearingPremolars—posterolateral to canines, have flat crowns with prominent ridges called cusps for crushing and grindingMolars—thickest and most posterior teeth, also adapted for crushing and grinding of ingested materialsPharynxShared by the respiratory and digestive systemsThree skeletal muscle pairs of pharyngeal constrictors (superior, middle, and inferior) form the wall of the pharynx and participate in swallowingCN X innervates most pharyngeal musclesBranches of external carotid arteries supply the pharynxInternal jugular veins drain the pharynxEsophagus/EsophagealsphinctersA tubular passageway that conducts ingested materials from the pharynx to the stomach.Passes through an opening in the diaphragm called the esophageal hiatus as it connects to the stomach.Approximately 25 cm long coursing anterior to the vertebral bodiesAbout 1.5 cm is in abdomen prior to changing into the stomachThe esophagus has two