The Digestive System
Nutrition
• Food provides the energy for metabolism and
the raw materials for building and repairing
body parts.
• The process of getting the food needed to
survive = nutrition.
– The raw materials the body gets from food =
nutrients.
• Carbohydrates, proteins, fats, vitamins, minerals and
water.
Process of Digestion
• The process of breaking down food into
smaller nutrient molecules by the digestive
system – digestion.
– 3 Main Functions:
1. Break down food into molecules the body can use.
2. Absorption of digested particles into the blood to be
carried throughout the body.
3. Removal of wastes from the body.
Types of Digestion
• 2 Types of Digestion:
– Mechanical Digestion – the physical breaking
apart of food particles into smaller pieces.
• Biting food, chewing, grinding and tearing
– Chemical Digestion – the digestion of food
particles by enzymes.
• Enzymes are proteins that speed up chemical reactions.
– Saliva, bile and stomach acids
The Path of Digestion
1.
2.
3.
4.
5.
6.
7.
Mouth
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum
Anus
1.
2.
3.
4.
5.
7.
6.
www.aboutkidsgi.org
Path of Digestion
1. Mouth
a. Food enters the digestive tract -ingestion.
i. Teeth chew and grind the food – mastication.
ii. Saliva mixes with food.
i.
The mass of chewed food is now called a bolus.
2. Esophagus
a. Transports food from the mouth to the stomach.
i. Esophagus is Greek for “to carry what is eaten”.
ii. Food is prevented from passing into the lungs by the
epiglottis.
o
As food passes over the epiglottis it covers the opening of the
trachea so food can’t pass down it.
Path of Digestion
iii. Food is moved down the esophagus by one-directional
muscular contractions - peristalsis
Path of Digestion
3. Stomach
a. The majority of the digestion taking place here is
MECHANICAL digestion.
i.
Muscular contractions break the food into smaller
pieces.
b. A smaller portion of the digestion taking place
here is chemical.
a. Food also mixes with gastric juices.
c. The liquid mass of food is now called chyme.
Path of Digestion
4. Small Intestine
a. 2.5 cm wide and over 6 meters long.
b. Food enters as a soft, watery substance - chyme.
c. Most digestion here is in the form of chemical
digestion.
i.
“Digestive helpers” help to break down the food
further by adding digestive enzymes here.
•
NO food passes through any of these organs!
d. Absorption of nutrients, by villi, into the blood
stream.
i.
Villi – fingerlike projections that increase the surface
area of the small intestine.
Villi
Digestive Helpers
A. Liver
•
The body’s largest and heaviest internal organ.
o
•
Located to the right of the stomach.
Produces the digestive enzyme bile.
o
Breaks up fat molecules.
B. Gallbladder
•
Small pea sized organ, green in color, that stores bile.
C. Pancreas
•
•
A triangular organ located between the stomach and the
small intestine.
Produces:
o
o
Insulin – controls sugar levels.
Pancreatic juices – breaks down proteins, starches and fats.
Digestive Helpers
Path of Digestion
5. Large Intestine
a. 6.5 cm wide and 1.5 meters long.
b. Most nutrients have been removed at this point
but indigestible materials and water remain.
i.
Water absorption is the main process taking place
here.
•
Body reuses the water to keep from becoming dehydrated.
ii. Material is turned into a solid waste product – feces.
iii. Natural bacteria in the large intestine help to break
down indigestible materials.
i.
Byproduct of these bacteria is gas.
Path of Digestion
6. Rectum
a. Stores the solid waste until its ready to be
released from the body.
7. Anus
a. The opening through which solid waste is
removed from the body.
Parastalsis Animation – 1:10min
Mechanical or Chemical Digestion?
Location/ Action
Mouth
Teeth
Saliva Glands
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum
Anus
Mechanical
Chemical
No Digestion