1. The Human Digestive System

2. Chemical Digestion of Food
Form when eaten
Form after digestion
Use the following words to label the diagram (in boxes):
Triglyceride
Monosaccharides
Amino Acids
Fatty Acids
Polypeptide
Polysaccharide
Disaccharide
Glycerol
Polypeptide
What is the name of the process represented by the arrows? __________________
Hydrolysis
Triglyceride

3. Where does the chemical digestion of each of the following occur?
Try to follow this during lecture/discussion and your reading. Return to & answer these questions after reading or lecture… We will not answer these just yet!
Carbohydrates (2 places) ______________________
Proteins (2 places) ________________________
Lipids ____________________________
Which enzyme(s) digest these molecules in each location? Add to answers above:
pepsin, amylase, lipase, trypsin, sucrase, lactase, peptidase

4. The Fours Stages of Food Processing
(Eating)
(Breaking down food MECHANICALLY & CHEMICALLY)
(Nutrients & water go from digestive system into BLOOD, to CELLS)
(Undigested food/solid waste leaves body as poop)

5. Your Digestive System is like the hole in a doughnut…
The Digestive system is like a tube that runs through the middle of your body.
Food goes in one end, and food waste comes out the other.

6. The Human Digestive System

7. How it begins…Mouth to Stomach
Mouth: Food is chewed (mechanical digestion) & moistened with saliva. Salivary amylase begins chemical digestion of starches (carbohydrates).
A slimy food ball (the bolus) leaves mouth, slides past epiglottis (covering opening to trachea) to the esophagus.
What happens if the epiglottis does not do it’s job??

8. Digestive Problem: Choking When you try to talk & eat at the same time…

9. How it begins…Mouth to Stomach
Esophagus: The bolus moves down this muscular tube by peristalsis (waves of muscle contractions), to the stomach.
Esophagus
PERISTALSIS
What happens when you do a handstand and try to eat a Gummi Bear, while upside-down?

10. In the Stomach
Stomach: Muscular sac that releases hydrochloric acid (HCl) & the enzyme Pepsin to begin digestion of proteins. Stomach lining is protected from acid by continually secreting protective mucus.
Digesting food kept in stomach by the lower esophageal sphincter (at entrance) and the pyloric sphincter (at exit).
Pyloric sphincter squirts partially digested mix of nutrients, water, & acid into the duodenum of the small intestine over 2-6 hours. This liquid is called chyme.

11. Digestive Problem: Acid Reflux & GERD
What happens when acid escapes the stomach into the esophagus? This is called Acid Reflux or “heartburn”.

12. Digestive Problem: Ulcers
Mucus can be eroded by several causes: H. pylori bacterium infection or stomach exposure to NSAIDs, asprin, alcohol, gastric hyper-acidity, cigarettes, etc.
Result: damage to cells lining stomach  gastric ulcer
Ulcers can also occur in the esophagus or the duodenum.

13. Completion of Digestion in Small Intestine
Small Intestine (duodenum)
Digestion of carbs, fats & proteins is completed using bile from liver & enzyme-filled pancreatic juice & intestinal juice.
Sodium bicarbonate from the pancreas neutralizes acidic chyme in duodenum. (not shown in picture)

14. Digestion is necessary for Absorption

15. Chemical Digestion Summary
Nutrient
Mouth
Stomach
Small Intestine
Carbohydrates (Starch)
Hydrolysis of starch into disaccharides begins (by salivary amylase).
Starch into disaccharides continues (by pancreatic amylase).
Disaccharides into monosaccharides (by maltase, sucrase, lactase, etc.)
Monosacchrides like glucose can now be absorbed.
Proteins
Large polypeptides into smaller polypeptides (by the enzyme pepsin).
Large polypeptides into smaller polypeptides (by trypsin, chymotrypsin).
Smaller polypeptides into amino acids (by peptidases).
Amino acids can now be absorbed.
Fats
Fat globules into fat droplets (by bile salts – emulsifiers, not enzymes…more like detergent).
Fats (triglycerides) into Fatty acids and glycerol (by lipase).
Fatty acids and glycerol can now be absorbed.
Note: Mechanical digestion of all nutrients occurs in all locations listed above.

16. Absorption of Nutrients in Small Intestine
Small Intestine (jejunum & ileum)
Absorption: Nutrient monomers are transported from lumen of small intestine into bloodstream, and from there to body’s cells.
Absorption helped by large surface area of small intestine, due to projections called villi, and their projections called microvilli.

17. Villi of Small Intestine

18. Where next?

19. Large Intestine: Absorption of Water & More!
Large Intestine: Colon
Remaining water is absorbed & undigested solids are compacted into feces (poop).
Home to mutualistic bacteria, like E. coli, which produce important vitamins (B vitamins, vitamin K)
Large Intestine: Rectum
Stores waste until elimination.

20. Problems/Diseases of Digestive System
Heartburn / Acid Reflux: HCl escapes stomach & “burns” lining of esophagus
Ulcer: “hole” in mucus & cells lining stomach, caused by HCl and H.Pylori bacterium
Lactose Intolerance: Inability to digest milk sugar, bloating & gas when dairy is consumed
Diarrhea: too much water in feces, frequent watery elimination
Constipation: not enough fiber in diet, infrequent elimination & compacted feces
Appendicitis: infection & inflammation of appendix
Gallstones: “stones” of bile salts in gall bladder, can be eliminated through narrow bile duct into digestive system (painful)
Celiac disease: cannot process gluten (a protein found in wheat), destroys villi & negatively affects nutrient absorption
Inflammatory Bowl Disease (IBD): chronic inflammation of all or part of your digestive tract. IBD primarily includes ulcerative colitis and Crohn's disease. Both usually involve severe diarrhea, pain, fatigue and weight loss. IBD can be debilitating and sometimes leads to life-threatening complications.*
Cancers of the digestive system, esp. colon or rectum (most common)
* From