1. Heterotrophic Nutrition & The Human Digestive System

2. Heterotrophic Nutrition
Heterotrophs are organisms who are unable to produce their own food and therefore must obtain food from an external source.
Examples:
Bacteria
Protozoans (amebas)
Fungi
Animals

3. Processes involved in Heterotrophic Nutrition
1. Ingestion – taking in food by mouth (eating)
2. Digestion – breaking down large molecules
into small ones
There are two types of digestion:
Mechanical digestion – food is broken down by cutting, grinding, and tearing.
Increase the food’s surface area for chemical digestion
Chemical digestion – large molecules are broken down into smaller ones by enzymatic hydrolysis.
Hydrolysis – splitting molecules by adding water
Digestion = Hydrolysis
3. Egestion – removal of undigested or
undigestible material.

4. Products of Chemical Digestion
Before Hydrolysis
After Hydrolysis
Complex Carbohydrates
Sugars
Proteins
Amino
Acids
Lipids
Fatty acids & glycerol

5. Human Nutrition Nutrients – substances an organism needs to live.
There are 6 basic nutrients in food.
Some must be digested before being absorbed:
Carbohydrates
Proteins
Lipids
Some do not have to be digested before being absorbed:
Vitamins
Minerals
Water

6. Human Nutritional Requirements
Nutrient requirements vary with age

7. What are some important Nutrients?
Roughage (Fiber, a carbohydrate) - indigestible materials in food (Fruits, vegetables, grains). Roughage stimulates proper functioning of muscles in the digestive tract.
Proteins are made from 20 different amino acids. We can synthesize 12 of those amino acids. The other 8 must be from our diet and are called the 8 essential amino acids.
Water is needed for chemical reactions to occur in the body.

8. Roles of Nutrients
Without vitamins and minerals, your body will not function properly.

9. Roles of Nutrients Not all forms of nutrients are good for you:
Saturated Fats - are solid at room temperature and are linked to cardiovascular disease.
Polyunsaturated Fats - are liquid at room temperature and are not linked to cardiovascular disease.

10. Human Digestive System
The human digestive system breaks down food into smaller molecules that can be absorbed into the blood and transported to cells throughout the body.
It is a one way tube that travels from the mouth to the anus.
Also called:
The Alimentary Canal
The Gastrointestinal Tract

11. Human Digestive System
Mouth
Salivary Glands
Liver
Gallbladder
Esophagus
Stomach
Pancreas
Small Intestine
Large Intestine
Anus
Rectum
Epiglottis
Salivary Glands
Salivary Glands
Mouth
Mouth
Esophagus
Esophagus
Epiglottis
Epiglottis
Liver
Liver
Stomach
Stomach
Gallbladder
Gallbladder
Pancreas
Pancreas
Small Intestine
Small Intestine
Large Intestine
Large Intestine
Rectum
Rectum
Anus
Anus

12. Human Digestive System
The Oral Cavity (Mouth) Structures & Functions
Teeth – perform mechanical digestion by tearing, crushing and grinding food into smaller pieces.
Salivary Glands – perform chemical digestion of carbohydrates through amylase (enzyme that digests starch).
Tongue – pushes food to the back of the mouth so it can be swallowed.

13. Human Digestive System
The Epiglottis
It is a flap at the back of the throat that covers the esophagus & trachea (windpipe).
It covers the trachea during swallowing to keep food from entering the respiratory system (prevents choking).

14. Human Digestive System
The Esophagus
A tube that connects the mouth to the stomach.
No digestion occurs here.
Food moves through by peristalsis (involuntary muscle contractions).

15. Human Digestive System
The Stomach
A muscular organ
Performs mechanical digestion (churns and mixes food)
Releases gastric juice (a mixture of HCl, hydrochloric acid, and proteases) to begin the chemical digestion of proteins.

16. Human Digestive System
The Small Intestine
A long, tubular organ (20–25 feet long)
Digestive enzymes are released into the small intestine from the gall bladder and pancreas.
All chemical digestion is finished here.
End products of digestion are absorbed through villi.
Peristalsis moves materials through the small intestine.

17. Human Digestive System
The Small Intestine - Villi
Villi are small finger-like projections in the small intestine.
They increase surface area in the small intestine.
Villi absorb products of digestion into the blood stream.

18. Human Digestive System
The Large Intestine
A tubular organ
(5 feet long)
No digestion occurs here.
Water is absorbed.
Undigested materials pass through and are left behind to be egested as feces.
Peristalsis moves materials through the large intestine.

19. Human Digestive System
The Rectum and Anus
The rectum stores feces before egestion.
Feces are egested through the anus.
No digestion or absorption occurs here.
Peristalsis moves materials through the rectum and anus.

20. Additional Structures of the Human Digestive System
1. Liver – produces bile, which emulsifies fats.
2. Gallbladder – stores bile and releases it into the small intestine.
3. Pancreas – produces proteases and releases them into the small intestine.

21. Human Digestive System
Emulsification
Emulsification is an example of mechanical digestion.
Bile emulsifies fats by breaking fat globules down into small droplets that can easily be chemically digested in the small intestine.
Fat
Globule
Bile
Fat Droplets

22. Disorders of the Human Digestive System
1. Ulcers - an erosion of the surface of the alimentary canal. Caused by bacteria, NOT stress!
2. Constipation - too much water is absorbed by the large intestine and egestion is difficult.
3. Diarrhea – too little water is absorbed by the large intestine, combined with increased peristaltic activity of the large intestine.

23. Disorders of the Human Digestive System
4. Appendicitis - inflammation of the appendix.
5. Gall Stones - hardened cholesterol deposits in the gall bladder. Blocks the release of bile into the small intestine.

24. Name that Body Part – Digestive System Edition!
Salivary Glands
Mouth (oral cavity)
Epiglottis
Tongue
Esophagus
Stomach
Liver
Pancreas
Large Intestine
Small Intestine
Rectum
Appendix
Anus