The Human Digestive System
Digestion
- Phases Include
- Ingestion
- Movement
- Mechanical and Chemical Digestion
- Absorption
- Elimination
Digestion
- Types
- Mechanical (physical)
- Chemical
- Enzymatic reactions to improve digestion of
- Carbohydrates
- Proteins
- Lipids
Digestive System Organization
- Gastrointestinal (Gl) tract
- Tube within a tube
- Direct link/path between organs
- Structures
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small intestine
- Large Intestine
- Rectum
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Mouth
- Teeth mechanically break down food into small pieces. Tongue mixes food with saliva (contains amylase, which helps break down starch).
- Epiglottis is a flap-like structure at the back of the throat that closes over the trachea preventing food from entering it.
Esophagus
- Approximately 10” long
- Functions include:
- Secrete mucus
- Moves food from the throat to the stomach using muscle movement called peristalsis
- If acid from the stomach gets in here that’s heartburn.
Stomach
- J-shaped muscular bag that stores the food you eat, breaks it down into tiny pieces.
- Mixes food with digestive juices that contain enzymes to break down proteins and lipids.
- Acid in the stomach kills bacteria.
- Food found in the stomach is called chyme.
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Small Intestine
- Small intestines are roughly 7 meters long
- Lining of intestine walls has finger-like projections called villi, to increase surface area.
- The villi are covered in microvilli which further increases surface area for absorption.
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Small Intestine
- Nutrients from the food pass into the bloodstream through the small intestine walls.
- Absorbs:
- 80% ingested water
- Vitamins
- Minerals
- Carbohydrates
- Proteins
- Lipids
- Secretes digestive enzymes
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Large Intestine
- About 5 feet long
- Accepts what small intestines don’t absorb
- Rectum (short term storage which holds feces before it is expelled).
Large Intestine
- Functions
- Bacterial digestion
- Ferment carbohydrates
- Protein breakdown
- Absorbs more water
- Concentrate wastes
Accessory Organs
- Not part of the path of food, but play a critical role.
- Include: Liver, gall bladder, and pancreas
Liver
- Directly affects digestion by producing bile
- Bile helps digest fat
- filters out toxins and waste including drugs and alcohol
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Gall Bladder
- Stores bile from the liver, releases it into the small intestine.
- Fatty diets can cause gallstones
Pancreas
- Produces digestive enzymes to digest fats, carbohydrates and proteins
- Regulates blood sugar by producing insulin
Fun Facts
- HOW LONG ARE YOUR INTESTINES? At least 25 feet in an adult. Be glad you're not a full-grown horse -- their coiled-up intestines are 89 feet long!
- Food drying up and hanging out in the large intestine can last 18 hours to 2 days!
- In your lifetime, your digestive system may handle about 50 tons!!
Now it's...
QUIZ TIME!
On a sheet of paper, write the
name of each colored organ:
- Green:
- Red:
- Pink:
- Brown:
- Purple:
- Green:
- Yellow:
How’d you do?
- Green: Esophagus
- Red: Stomach
- Pink: Small Intestine
- Brown: Large Intestine
- Purple: Liver
- Green: Gall Bladder
- Yellow: Pancreas
Great Job!
References and Links
- Your Digestive System and How It Works
- Digestive system diagram comes from this site
- The Real Deal on the Digestive System
- Pancreas: Introduction and Index
- Your Gross and Cool Body - Digestive System
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A good way to describe peristalsis is
an ocean wave moving through the muscle.
These diagrams don’t separate the esophagus
from the mouth functions, you might want
to talk about what happens in the
mouth too.
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The stomach takes around 4 hours to
do it’s job on the food, depending
on what kinds of food are digested.
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Depending on the maturity of the group,
you can talk about the feces leaving
via the anus.
Mention the appendix at the bottom of
the ascending colon and that it might
have been used long ago but is not
today
Mention the portions of the large intestine,
ascending, transverse, descending, sigmoid, and
rectum (last one if the audience is
mature enough)
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Livers can regenerate missing pieces if
necessary. Is one of the largest organs
in the body.
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Explain to students that removing the
stones typically means removing the gallbladder,
but that the body eventually adjusts to
not having the bile stored.
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Explain the difference between the two
types of diabetes. In type 1, the
pancreas fails to produce enough insulin.
In type 2, the body stops responding
properly to the insulin it creates.
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