1. Nutrition
Why do we eat?
The foods we eat provide the nutrients our bodies need for energy, growth, and tissue repair.
Digestion is the process of breaking down food in order to extract the nutrients and make them useable by the body.

2. Types of Nutrients (You should know these!)
Micronutrients- vitamins & minerals
Macronutrients- proteins, fats, carbohydrates

3. And water…

4. Four Stages of Digestion
Ingestion
Digestion
Absorption
Egestion

5. Four Stages of Digestion
Ingestion
taking substances into the body through the mouth
Digestion
Absorption
Egestion

6. Four Stages of Digestion
Ingestion
Digestion
The breaking-down of large, insoluble food molecules into small water-soluble molecules.
Absorption
Egestion

7. Digestion… begins in the mouth
MECHANICAL DIGESTION
The teeth breaks up food &
the tongue moves it around

8. Digestion… begins in the mouth
2) CHEMICAL DIGESTION
saliva
amylase: an enzyme that
digests starch
mucin: a protein present in
mucus that protects soft lining of digestive system and lubricates food for easier swallowing
buffers: neutralize acid to prevent tooth decay
anti-bacterial chemicals: kill bacteria that enter mouth with food

9. Which type of digestion is the following?
Chewing a saltine? -
2. Saliva breaking the saltine down into molecules of glucose? -
3. Your tongue breaking pieces of a hamburger apart?
4. Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids?
Mechanical
Chemical
Mechanical
Chemical

10. Digestion… then moves to the esophagus
The esophagus is a muscular tube that carries food and liquids from the mouth to the stomach.

11. Esophagus
Food moves through the Esophagus to the Stomach by Peristalsis
Peristalsis: a series of involuntary wave-like muscle contractions which move food along the digestive tract

12. Digestion… then moves to the stomach
The stomach stores swallowed food and liquid, mixes the food and liquid with digestive juice it produces, and slowly empties its contents, called chyme, into the small intestine.

13. Four Stages of Digestion
Ingestion
Digestion
Absorption
movement of digested food molecules through the wall of the intestine into the blood
Egestion

14. Absorption… begins in the small intestine
The walls of the small intestine absorb the digested nutrients into the bloodstream. The blood delivers the nutrients to the rest of the body.

15. Small intestine duodenum = mostly digestion
Structure: 3 sections
duodenum = mostly digestion
jejunum = absorption of nutrients & water
ileum = absorption of nutrients & water
About every 20 seconds, the stomach contents are mixed by the churning action of smooth muscles.
As a result of mixing and enzyme action, what begins in the stomach as a recently swallowed meal becomes a nutrient-rich broth known as acid chyme.
At the opening from the stomach to the small intestine is the pyloric sphincter, which helps regulate the passage of chyme into the intestine.
A squirt at a time, it takes about 2 to 6 hours after a meal for the stomach to empty.

16. Absorption… and finishes in the large intestine
The large intestine absorbs water and any remaining nutrients and changes the waste from liquid into stool.

17. Rectum Last section of colon (large intestine)
Stores feces (undigested material) for elimination
mainly cellulose
from plants
roughage or fiber

18. Four Stages of Digestion
Ingestion
Digestion
Absorption
Egestion
passing out of food that has not been digested, as feces, through the anus

19. Egestion…
The elimination or removal of undigested or waste material from a cell or organism.