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The Digestive System
The function of the digestive system is to
convert foods into simpler molecules that
can be absorbed and used by the cells of
the body.
Two types of Digestion
Mechanical (physical) digestion is the
process of breaking the food into smaller
pieces but not changing its chemical
properties.
Mouth (chewing)
Stomach (squashing)
Chemical digestion is when foods interact
with hydrochloric acids (HCl) and enzymes
to breakdown into molecules that the body
can use for energy - sugars, proteins & lipids.
Mouth (saliva)
Stomach (HCl)
Small Intestine (enzymes)
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Mouth: Where digestion begins. Teeth tear and crush
food to be swallowed. (Mechanical Digestion)
Villi: microscopic, finger-like projections that line
Saliva begins to chemically digest food.
the small intestine. Covered in capillaries and
pass nutrients on to the bloodstream.
Esophagus: "food tube". Food moves down the
esophagus by muscle contractions called peristalsis.
Large Intestine: Stores, compacts and eliminates
Stomach: food from the esophagus empties into a
materials that cannot be digested; water is
absorbed from the large
intestine
large muscular sac called the stomach. The stomach
continues both mechanical and chemical digestion.
The stomach squashes food, while the HCl chemically
breaks down food. Stomach is lined w mucus to protect
from the HCl.
This new soupy mush is call chyme.
Digestion Helpers:
Pancreas: Secretes insulin; neutralizes acids
Liver: Breaks down toxins in blood; makes bile
Gallbladder: Stores bile
Small Intestine: The chyme is slowly released into
the small intestine. Most chemical digestion occurs
here. Nutrients are absorbed into the bloodstream
through the small finger like extensions called villi.
The Digestive System
The function of the digestive system is
to convert foods into simpler
molecules that can be absorbed and
used by the cells of the body.
Two Types of Digestion Occur
Mechanical
Chemical
Mouth (chewing)
Stomach (squashing)
Mouth (saliva)
Stomach (HCl)
Small Intestine (enzymes)
Mechanical (physical) Digestion
Mechanical (or physical) digestion is the
process of breaking the food into smaller
pieces but not changing its chemical
properties.
This is an apple.
Is it still an apple?
How about now, is
it still an apple?
Chemical Digestion
Foods interact with hydrochloric acid
(HCl) and enzymes to breakdown into
molecules the body can use for energy,
such as sugars, proteins and lipids (fats).
The Mouth
• The teeth tear and crush food into amounts small
enough to be swallowed. Chewing begins the
process of mechanical digestion.
• As you chew, the food gets mixed with a liquid
called saliva. Saliva contains an enzyme that
begins the chemical digestion process.
Esophagus
• Once the food becomes mush, it is
pushed down into the throat by the
tongue. This leads into a long tube
called the esophagus, which leads
to the stomach.
• Food does not travel down by
gravity but rather by muscle
contractions called peristalsis (per
uh STAHL sis).
Stomach
• Food from the esophagus empties into a large
muscular sac called the stomach. The stomach
continues both mechanical and
chemical digestion.
• The stomach continues to squeeze food –
mechanical digestion. While glands secrete
enzymes (Pepsin) and acids (Hydrochloric Acids)
– chemical digestion.
• This new soupy mush is called chyme (kiem),
Small Intestine
• The chyme is slowly released into the small
intestine. Most of the chemical
digestion occurs here, nutrients are
absorbed into the bloodstream.
• The small intestine is lined with finger like
extensions called villi (villus – singular).
Villi
• Finger-like projections that line the small
intestine. They are covered in capillaries
that pass nutrients on to the bloodstream.
Digestion Helpers
Food does not pass through these organs. They produce
fluids that help breakdown foods.
Pancreas:
–
–
Bicarbonates to neutralize acids
Insulin helps regulate blood sugar level
Liver:
–
–
–
–
Stores nutrients
Breaks down toxins in the blood
Makes cholesterol for cell membranes
Makes green liquid (bile) used in to digest fats.
Bile is stored in the gallbladder.
Large Intestine
Stores, compacts and eliminates materials that
cannot be digested; water is absorb out of wastes.
“Good” bacteria are present in the large intestine.
These help prevent disease, produce some key
vitamins, aid in digestion.
When the doctor prescribes
antibiotics to cure an ear
infection or respiratory
infection, how can this have a
negative affect on our
digestive system? What can
be done to help?
Review
The purpose of the digestive system is to:
Convert foods into molecules that can be used by the body
Mechanical digestion takes place in these two places:
Mouth and Stomach
Where does chemical digestion takes place?
Mouth, stomach and small intestines
True or False: Food enters the esophagus then gravity forces
it down into the stomach False
How does the villi in the small intestine compare to
the alveoli in the respiratory system?