1. Food’s journey through the . . .
DIGESTIVE SYSTEM

2. Digestion Digestion breaks food molecules down into smaller molecules
It is necessary to make smaller molecules because these nutrients need to be used by CELLS.
Only small molecules can pass through the cell membrane and into the cell so it can be used.
EX: We break starch ( a large molecules) down into glucose (a small molecule that can cross cell membranes) so our cells can do respiration and make energy!

3. What are each of the following broken down into???
Digestion
What are each of the following broken down into???
Proteins →
Starch →
Lipids →
Carbohydrates →
Steps of Digestion:
Ingestion → Digestions → Absorption → Excretion
Amino Acids
Glucose
Fatty Acids
Simple Sugars

4. Types of Digestion
Mechanical – physically breaking food down into smaller pieces
This creates more surface area, so enzymes can get to more molecules
Chemical – use of chemicals and enzymes to break food into substances that can be absorbed

5. Mouth Teeth are used for mechanical digestion to break the food into
smaller pieces, so it can be easily
swallowed.
Saliva contains an enzyme (amylase) used in chemical digestion, which breaks down starches into simple sugars
The tongue is your strongest muscle used to manipulate food during mastication

6. Esophagus The tube the food travels down to get to the stomach
Peristalsis is the motion that pushes the food down the tube. The tube pinches off above the food pushing it toward the stomach
You have an epiglottis that covers your esophagus while you are breathing and covers your trachea while you are swallowing
This prevents food from “going down the wrong tube”

7. Stomach The stomach performs mechanical and
chemical digestion of food.
The stomach secretes a powerful acid (pepsin) that breaks food down
It also churns mixing the food with the acid and breaking it down mechanically
Chyme is the mixture of stomach acid (pepsin), broken down food, and saliva that flows from the stomach into the small intestine

8. Duodenum
This is the first section of the small instestine, where most of the chemical digestion of carbohydrates, lipids, and proteins occurs
Chyme is joined with enzymes from the liver and pancreas that reduce acidity of the chyme and chemically digest the food

9. Small Intestine
The small intestine are covered in little finger like projections called villi
Villi increase the surface area of the small intestine to increase absorption of nutrients
The usable nutrients are removed from the chyme and travel across the villi into the blood vessels that are inside it

10. Large Intestine When the food arrives in the
large intestine it is nutrient free
The large intestine pulls any excess water out of the remaining indigestible material creating feces
The large intestine is filled with bacteria that help our digestion process
When the large intestine is not removing enough water, diarrhea will result
When the large intestine removes too much water, constipation will occur

11. Rectum The rectum will store the
feces until there is enough to pass out of the body
When the rectum is full, you feel the urge to go to the bathroom
There is a sphincter muscle at the bottom of the rectum called the anus
This squeezes shut to keep feces in the rectum and expands to allow it out when passing a stool

12. Liver, Pancreas, & Gallbladder
The liver and pancreas secrete
enzymes and digestive fluids that
mix with the chyme in the duodenum
The pancreas secretes a fluid to neutralize the acidity of the stomach acid
The liver secretes bile, which is
used to break down fatty acids
(lipids)
Bile is stored in the gallbladder

13. Appendix Is located near the junction of the small and large intestine
The appendix is a vestigial organ, which means it was once used but shrunk in size as it became less useful
Some organisms use the
appendix to help break down
cellulose in very fibrous
substances (leaves)

14. Common Diseases
What diseases or problems do you think of when you think of the digestive system?
Diarrhea
Constipation
Appendicitis
GERD
IBS
Ulcers
Cirrhosis
Diverticulitis
Ulcerative Colitis
Hemorrhoids
Celiac’s
Lactose Intolerance
Stomach Ache

15. Diarrhea and Constipation
Diarrhea – too much fluid in the bowel movements
Caused by the large intestine not removing enough water
Can be caused by viruses, bacteria, etc.
Can lead to dehydration and eventually death
Constipation – too much water being removed from the bowel movements
Can be caused by poor diet or not taking in enough water
Symptoms can be alleviated by taking laxatives