Mouth Pharynx Esophagus Stomach Small intestine Large intestine Salivary glands liver pancreas and gall bladder are accessory organs Main functions digestion Food is broken down Mechanically chewing bowl movements ID: 999329
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1. Digestive System
2. Organs of the alimentary CanalMouthPharynxEsophagusStomachSmall intestineLarge intestine* Salivary glands, liver, pancreas and gall bladder are accessory organs
3. Main functions:digestionFood is broken down:Mechanically (chewing, bowl movements)Chemically (enzymes, acids)2. AbsorptionFood is absorbed from small intestine bloodbody3. Excretion
4. MouthFood enters DT through the oral cavity (lined with mucous membranes)Lips (labia) protect its openingCheeks form the lateral wallsHard palate forms anterior roofSoft palate forms posterior roofUvula: fingerlike projection of soft palateTongue occupies the floor of the mouthLingual frenulum (fold of mucous membrane) secures tongue to floor of moth and limits its posterior movements
5. Mouth cont.Both types of digestion mechanical and chemicalSalivary glands secrete enzymes that break carbohydratesTeeth help break down food by chewing
6. Mouth (salivary glands)Three pairs of salivary glands secrete saliva into the mouthParotid glands:Located close to our ears Submandibular glands below the mandibleSublingual glandsUnder the tongueSaliva is a mixture of mucus and serous fluidsMucus moistens +helps bind food together into a mass called bolus which eases swallowingThe serous portion contains an enzyme, amylase which begin starch digestionSaliva also contains Abs which inhibit bacteria
7. Pharynx and EsophagusFood passes from oral cavity to the pharynx esophagus stomachEsophagus is lined with mucous membranes to allow food to pass easilyEpiglottis flips over the trachea to keep food from entering the trachea
8. Pharynx and Esophagus cont.Swallowing:A bolus of food is pressed backward into the pharynx by the tongue. This is the only step that is voluntary - the remaining steps occur by reflex.Once the bolus reaches the pharynx several actions are initiated, the epiglottis swings backward to cover the larynx. The tongue presses backward and a peristaltic contraction in the pharynx propels the bolus into the esophagus, where the actual act of swallowing takes place.
9. Esophagus HistologyMucosa:Innermost, moist layer that lines the cavity (lumen) of the organConsists of surface epithelium (stratified squamous)+ small amount of CT (lamina propria) +SM layer*beyond the esophagus all epithelium is simple columnarSub mucosa:covers the mucosaSoft C.T layer contains BV, nerve endings, lymphaticsMuscularis externa:2 Layer of SM cells (longitudinal muscle layer + circular muscle layer)Serosa:Outer most layerSingle layer of serous fluid producing cells- visceral peritoneum- covers the external surface of the esophagusMesentery is a membrane extension of the visceral peritoneum
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