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Digestive System

Digestive System. Mouth. Pharynx. Salivary glands. Esophagus. Liver. Stomach. Pancreas (behind stomach). Gallbladder (behind liver). Large intestine. Small intestine. Rectum.

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Digestive System

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  1. Digestive System

  2. Mouth Pharynx Salivary glands Esophagus Liver Stomach Pancreas (behind stomach) Gallbladder (behind liver) Large intestine Small intestine Rectum Digestion - breaking down food into small molecules that can be passed into your cells. Includes all organs below: Section 38-2 • Alimentary Canal - a one-way tube that passes through the body. • (mouth, pharynx, stomach, small intestine, large intestine.) • Accessory structures -do not carry food, but aid in digestion.(salivary glands, pancreas, liver)

  3. 1. The Mouth: • Teeth - tear/crush food • Mechanical digestion - physical breakdown of food • Chemical digestion - enzymes break food into smaller food molecules. Ex:starch into glucose • Saliva - moistens food • Enzyme = salivary amylase - breaks down starches into simple sugars • Food passes through throat past the epiglottis • Q: Do enzymes get used up in these chemical reactions? • A: No. • Q: What is their optimal temperature and pH? • A: In humans, 98.6 degrees, and neutral to slightly basic, except for stomach enzymes.

  4. 2. The Esophagus: • Muscular tube connecting pharynx to stomach • Moves through peristalsis = rhythmic waves of muscular contractions • Squeezes food ball along esophagus • Can swallow even when standing on your head! • Can begin in absence of food = “lump in your throat.” • Food bolus enters stomach through a sphincter (ring of muscle) • When sphincter fails to close, acidic gastric juice may splash up into esophagus = “heartburn.”

  5. 3. The Stomach- • Football shaped, holds 1 liter • Mechanical - smooth muscles churn and mix food • Lining of stomach produces mucus-lubricates/protects stomach wall • Chemical - lining contains gastricglands which produce: • HCl - kills bacteria,activates pepsin • Enzyme: Pepsin - breaks proteins into smaller polypeptides/amino acids. • Enzyme: Rennin -curdles milk protein • Final pH of gastric contents = 2. • Chyme - mixture that stomach produces • 1-2 hours - out pyloric sphincter valve • (Water, salts, alcohol, some drugs - can be absorbed through stomach) • Peptic Ulcer - stomach lining is digested/hole in wall. Most caused by a bacteria,cured with antibiotics.

  6. Helicobactor pylori Bacteria causing stomach ulcer

  7. 4. The Small Intestine - 6 m long x 3 cm wide • Chyme enters the duodenum - (1st of 3 parts of small intestine.) Enzymes enter here from: • Liver - makes bile which emulsifies fats (breaks into small droplets). • Gall Bladder - stores bile • Q:What are gall stones? • Q: Can you live without your gallbladder? • Pancreas - makes 3 enzymes: • Pancreatic Amylase - breaks starch into simple sugars • Trypsin - breaks proteins into A.A. • Lipase - breaks fats into fatty acids & glycerol • Small Intestine enzymes: • Maltase, sucrase, lactase - breaks down sugars (disaccharides) into simple sugars (monosaccharides) • Peptidase - breaks down proteins into A.A. • Q: Can you live without your liver or pancreas? Click to enlarge diagram

  8. A Close-up: Substances entering the Duodenum

  9. Liver Bile duct Pancreas Gallbladder Pancreatic duct Duodenum To rest of small intestine  The Liver and the Pancreas Section 38-2

  10. Absorption in the Small Intestine: • After duodenum: Jejunum and Ileum (total 6 meters long) • Here are villi - fingerlike projections covered with microvilli. • These folds and projections provide large surface area for absorption of nutrients. • If the lining were completely unfolded and spread out, it would be the size of a tennis court! • Carbs and Proteins - go from villi to capillaries to cells • Fats - go from villi to lymph vessels to cells • Now all that is left is water, cellulose, & other undigestible substances.

  11. Circular folds Epithelial cells Villi Capillaries Lacteal Vein Artery  The Small Intestine Section 38-2 Villus Small Intestine

  12. Villi and Microvilli in the Small Intestine

  13. 5. The Large Intestine/Colon - • These substances pass into appendix, a small saclike organ • Clogged and inflamed = appendicitis. Removal needed. • Large Intestine -11.5 long x 5 cmwide - removes water from undigested material • Bacteria in colon produce needed compounds, including Vitamin K. • Antibiotics can destroy these beneficial bacteria. (Eat yogurt!) • Next - eliminate wastes. Go out rectum and anus = feces • Disorders: • Diarrhea - not enough water is absorbed. • Constipation - too much water is absorbed - stays in colon too long.(Eat fiber!) • Colon polyps or cancer

  14. Review: Can you trace this apple through the digestive system, naming each organ and enzymes involved?

  15. Up Next: Now that we have digested, how do we excrete our liquid wastes?

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