Digestive system

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Digestive system

  1. 1. Digestive system Food substances are changed into forms that can be absorbed through cell membranes
  2. 2. Basic divisions <ul><li>Alimentary canal - extends from mouth to anus </li></ul><ul><li>Accessory organs - release secretions into canal </li></ul>
  3. 3. Alimentary Canal <ul><li>muscular tube, 9 meters long </li></ul><ul><li>Substances move through it by peristalsis </li></ul><ul><li>Sphincter muscles – circular muscles that control movement of food from one section to another </li></ul>
  4. 4. <ul><li>Mouth – mechanically reduces size of solid particles, mixes them with saliva </li></ul><ul><li>a.     Cheeks – muscular </li></ul><ul><li>b.     Lips – muscular, have sensory receptors c.     Tongue – muscular, mix food particles, taste, move to back of pharynx </li></ul><ul><li>d.     Palate – roof of oral cavity, hard anterior, soft posterior </li></ul><ul><li>e.     Uvula – structure that hangs down in the back of the throat, seals nasopharynx while swallowing </li></ul><ul><li>Teeth – primary; 20(deciduous) permanent; 32 </li></ul>
  5. 5. <ul><li>Pharynx – connects nasal and oral cavities with larynx and esophagus </li></ul><ul><li>Esophagus – straight, collapsible tube 25cm long, provides a passageway for substances between pharynx and stomach </li></ul><ul><li>Stomach – J-shaped; can hold 1 liter of food; inner lining is folded until distended. Functions to receive food, mix it with gastric juices , begin digestion of proteins, do a little bit of absorption, and move food into small intestine </li></ul>
  6. 6. <ul><li>Small Intestine – Completes digestion, absorbs products, and transports leftovers to large intestine. Lined with villi – small fingerlike projections that increase surface area. </li></ul><ul><li>Large Intestine – reabsorbs water and electrolytes; forms and stores feces until defecation. Includes the colon, rectum, and anus </li></ul><ul><ul><li>Feces – materials that were not digested or absorbed, together with water, electrolytes, and bacteria. 75% water; color is due to bile pigments; odor due to bacteria and their products </li></ul></ul><ul><ul><li>Appendix – near the beginning of the colon </li></ul></ul>
  7. 7. Accessory Organs <ul><li>Salivary Glands – secrete saliva ; moistens food particles, holds them together, and begins digestion of carbohydrates </li></ul><ul><li>Pancreas – secretes digestive enzymes that digest carbohydrates, fats, proteins and nucleic acids (exocrine function) </li></ul>
  8. 8. <ul><li>Liver – located below diaphragm, mostly on the right side </li></ul><ul><ul><li>Metabolism of carbs, lipids, & proteins </li></ul></ul><ul><ul><li>Storage of substances (glycogen) </li></ul></ul><ul><ul><li>Filtering of blood – esp. from intestines </li></ul></ul><ul><ul><li>Destruction of toxic chemicals </li></ul></ul><ul><ul><li>Secretion of bile (emulsifies fats) </li></ul></ul><ul><li>Gall Bladder – pear shaped green sac attached to liver </li></ul><ul><ul><li>Stores bile between meals </li></ul></ul><ul><ul><li>Concentrates bile by reabsorbing water </li></ul></ul><ul><ul><li>Releases bile into small intestine </li></ul></ul>
  9. 9. Sphincters <ul><li>Esophageal – between esophagus and stomach </li></ul><ul><li>Pyloric – between stomach and sm. Int. </li></ul><ul><li>Ileocecal – between large and sm. Int. </li></ul><ul><li>Anal – 2 sets between rectum and anus </li></ul>

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