1. Standard 4.1
Explain generally how the digestive system converts macromolecules from food into smaller molecules that can be used by cells for energy and for repair and growth.

2. Essential Questions:
Describe the process of digestion in the digestive system.
Recognize that macromolecules are converted into smaller molecule that can be used at the cellular level.
Recognize the importance of enzymes in the proper functioning of the digestive system.

3. Essential Vocabulary
Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, mechanical digestion, chemical digestion, liver, pancreas, gall bladder

4. Nutrition Water- site of chemical reactions in cells
Carbohydrates- main source
of energy
Fats- produce cell membranes, nervous system tissue, hormones, vitamin absorption, body insulation, and storage of excess energy

5. Nutrition
Proteins- materials for growth and repair of tissues, transport and regulatory functions
Vitamins- work with enzymes to
help regulate body processes
Minerals- structure of tissues and help specific body processes

6. Learning Check What are the six nutrients required by the human body?
Water, carbohydrates, fats, proteins, vitamins, minerals

7. Digestive System
Breaks food down into small molecules that can be used by cells
Mechanical Digestion – chewing; large pieces of food broken down into smaller pieces that can be processed
Chemical Digestion – Various enzymes and other chemicals break food down to smaller and smaller molecules

8. Learning Check What are the two kinds of digestion?
Mechanical and Chemical

9. Alimentary Canal The organs through which food actually passes:
Mouth, pharynx, esophagus, Stomach, Small intestine, Large intestine, rectum

10. Gallbladder (behind liver)
Major Organs
Mouth
Salivary glands
Stomach
Pancreas (behind stomach)
Large intestine
Small intestine
Rectum
Gallbladder (behind liver)
Liver
Esophagus
Pharynx

11. Mouth First entry point for food.
Teeth- mechanical digestion- food broken down into smaller pieces
Saliva- moistens food; contains amylase (an enzyme that breaks down starch)
Tongue- muscle that forms the bolus (ball of food that can be swallowed).

12. Learning Check What is the function of the enzyme amylase?
To increase the rate at which starch is broken down

13. Esophagus Food from mouth passes through pharynx (throat) to esophagus
Esophagus- Long tube that connects the mouth and stomach.
Peristalsis- rhythmic muscle contractions that move bolus (food) down to stomach.

14. Functions of the stomach
Bulk storage of undigested food
Mechanical breakdown of food (churning)
Chemical digestion- Disruption of chemical bonds via acids and enzymes
Production of chyme (liquefied food mixed with gastric juices)

15. Digestion and absorption in the stomach
Preliminary digestion of proteins
Pepsin
Permits digestion of carbohydrates
Very little absorption of nutrients

16. Learning Check
What is chyme?
Liquefied food mixed with gastric juices

17. Small intestine Important digestive and absorptive functions
Secretions and buffers provided by pancreas, liver, gall bladder
Three subdivisions:
Duodenum - digestion
Jejunum – digestion and absorption
Ileum - absorption

18. Regions of the Small Intestine
Figure 24.16a

19. Functions of Small Intestine
Completion of enzymatic break down of food- enzymes from pancreas.
Food molecules are absorbed into the blood and transported to cells
Small intestine is long (6 meters) and highly folded to allow for this absorption.
Villi- finger-like projections inside the small intestine that increase surface area for absorption

20. Small Intestine Villus Circular folds Epithelial cells Villi
Capillaries
Lacteal
Vein
Artery

21. Learning Check What are the two main functions of the small intestine?
Break down of food and absorption of food molecules

22. Functions of the large intestine
Water is reabsorbed into the blood
Undigested food in compacted into feces
Absorbs vitamins produced by bacteria
Stores fecal matter prior to defecation

23. The Large Intestine
Figure 24.23a

24. Learning Check What is the main function of the large intestine?
Absorption of water

25. The rectum Last portion of the digestive tract
Terminates at the anal canal
Release of solid wastes (feces)

26. Accessory Organs Liver Pancreas Gallbladder To small intestine
Duodenum
Bile duct
Pancreas
Pancreatic duct
To small intestine

27. The pancreas Digestive functions
Pancreatic juice secreted into small intestine
contains sodium bicarbonate to neutralize stomach acid
contains various enzymes
Carbohydrases- break down carbohydrates
Lipases- break down lipids
Proteolytic enzymes- break down proteins

28. Digestive Enzymes Site Mouth Stomach Small intestine (from pancreas)
Role in Digestion
Salivary amylase
Pepsin
Amylase
Trypsin
Lipase
Maltase, sucrase, lactase
Peptidase
Breaks down starches into disaccharides (carbohydrates)
Breaks down proteins into large peptides
Continues the breakdown of starch (carbohydrates)
Continues the breakdown of protein
Breaks down fat (lipids)
Breaks down remaining disaccharides into monosaccharides (carbs)
Breaks down dipeptides into amino acids. (proteins)

29. Learning Check
Why does chyme from the stomach need to be neutralized in the small intestine?
Chyme is very acidic

30. Liver
Produces bile and sends it to the gall bladder and small intestine.
Bile is a fluid that breaks apart the fats found in fatty foods- mechanical digestion
enzymes can then break down the fats into individual molecules - chemical digestion

31. The gallbladder Hollow, pear-shaped organ
Stores, modifies and concentrates bile from the liver
Releases bile to the small intestine after meals

32. Summary Alimentary canal:
Mouth, 2. pharynx, 3. esophagus, Stomach, 5. Small intestine,
6. Large intestine, 7. rectum
Accessory Organs:
Pancreas, liver, gallbladder
**All organs of the digestive system work together to break down food into molecules that can be used by cells.