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The Digestive System

The Digestive System. The Digestive System. 4 steps for processing nutrients from food Ingestion Digestion Absorption Elimination. Ingestion & Digestion. Ingestion: Eating or drinking Digestion: the breaking down of food into molecules that are small enough to be absorbed by the body

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The Digestive System

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  1. The Digestive System

  2. The Digestive System 4 steps for processing nutrients from food • Ingestion • Digestion • Absorption • Elimination

  3. Ingestion & Digestion Ingestion: Eating or drinking Digestion: the breaking down of food into molecules that are small enough to be absorbed by the body Mechanical digestion: Chewing and grinding food into smaller pieces, increasing the surface area Chemical digestion: Breaking chemical bonds of macromolecules (carbs, proteins and lipids) into monomers (sugars, amino acids, glycerol & fatty acids) • Hydrolysis reactions that are carried out by enzymes

  4. Absorption & Elimination Absorption: • Cells absorb small molecules (monomers) allowing them to enter into the circulatory system for immediate use or be transported to storage organs for later use Elimination: • Removing undigested waste (feces)

  5. Digestive System Digestive Tract • A.k.a. an alimentary canal (2 openings) • The mouth, pharynx, esophagus, stomach, small intestine, and large intestine Accessory Glands & Organs • Aid in digestion, but not a part of the digestive tract • Salivary glands, pancreas, liver, gallbladder. • Secrete digestive juices and enzymes into the digestive tract

  6. What’s Your Size?

  7. Mouth • Plays a role in ingestion and digestion • Teeth, tongue, hard palate aid in mechanical digestion • Tongue moves food down to the esophagus • Salivary glands aid in chemical digestion • Release saliva (~1L/day), a watery liquid containing digestive enzymes • Salivary amylase begins to break down starch into smaller carbohydrates • Lubrication Chewed up food is now called a bolus

  8. Esophagus • Located behind the trachea • As you swallow, the epiglottis closes over the tracheaand the food bolus passes through pharynx into the esophagus • The bolus is pushed through the esophagus by a series of muscle contractions called peristalsis

  9. Heart Burn • After food passes into the stomach, the cardiac sphincter closes the esophagus • If the sphincter opens at an inappropriate time, stomach acid can flow back into the esophagus • Esophagus does not have the same protective lining as the stomach

  10. Stomach I ate too much…I’m STUFFED! • Elastic, muscular sac with a protective lining that contains millions of gastric glands • Can ~ 2 L • Mechanical and chemical digestion

  11. Stomach Chemical Digestion: • The hormone, gastrin, stimulates gastric glands to release gastric juice • Hydrochloric acid breaks apart cells and kills bacteria • Enzymes e.g. pepsin • Mucus lubrication and protection Mechanical Digestion: • Stomach muscles churn • Bolus becomes an acidic, nutrient-rich liquid called chyme

  12. Small Intestine • Chyme passes through the pyloric sphincter and enters the small intestine (peristalsis) • Long, narrow tube where digestion is completed and absorption begins • 3 parts: • Duodenum • Jejunum • Ileum

  13. Duodenum • Bile from the liver and gallbladder are secreted into the duodenum to help with lipid digestion • Pancreas secretes pancreatic juice into the duodenum • Neutralizes acidic chyme • Pancreatic amylase • Trypsin & chymotrypsin (protein digestion) • Pancreatic lipase • Small intestine releases enzymes too

  14. Jejunum & Ileum Jejunum • Contains more villi, therefore more absorption • Breakdown of remaining polypeptides and carbohydrates Ileum • Absorption • Push remaining undigested material into the large intestine

  15. Large Intestine • Undigested material passes through the sphincter between the ileum and the cecum • Absorption of water and dissolved minerals • Intestinal bacteria produce vitamins • Indigestible material (feces) passes through the rectum to the anus • Anal sphincters help control timing of elimination

  16. Increased Surface Area • The small and large intestine are folded to  surface area and therefore  absorption • Within the folds, there are finger-like projections called villi • Lacteal absorbs fats and fat-soluble vitamins • Capillaries absorb glucose, amino acids, minerals and water-soluble vitamins

  17. Regulation of Digestive Processes

  18. http://www.neok12.com/php/watch.php?v=zX680f4e7e6e7c420f746402&t=Digestive-Systemhttp://www.neok12.com/php/watch.php?v=zX680f4e7e6e7c420f746402&t=Digestive-System • http://www.neok12.com/quiz/DIGSYS04 • http://www.neok12.com/quiz/DIGSYS01 • http://www.neok12.com/diagram/Digestive-System-01.htm

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