Transcript The Digestive System

The Digestive System
What is it?
• The digestive or gastrointestinal tract is
about 30 feet long.
• It extends from the mouth to the anus.
• It contains many parts that work together
both mechanically and chemically to help
the body use food.
The Digestion Process
• Two phases:
– Mechanical Phase
– Chemical Phase
Mechanical Phase
• Begins in the mouth.
• The teeth chew the food and break it down
into smaller pieces.
• These contractions mix food particles and
break them into smaller pieces. Then with
waves of contractions called peristalsis
muscles also push food through the
digestive tract.
Interesting Facts
• Emotions such as sadness, depression,
and fear can slow down the peristalsis
• Anger and aggression can speed up
peristalsis.
The Chemical Phase
• Also begins in the mouth.
• As you chew food is mixed with saliva,
which is a mucus and enzyme containing
liquid secreted by the mouth. It moistens
food particles helping them move down
the esophagus into the stomach. It also
begins to break down starches.
The Chemical Phase
• In the stomach gastric juices containing
hydrochloric acid and several enzymes are
secreted. These juices break down the
food further.
• An ordinary meal leaves the stomach in
about 2 to 3 hours.
– Carbohydrates first
– Proteins second
– Fats third
The Chemical Phase
• As digestion continues the semiliquid food mass
leaves the stomach and enters the small
intestine. Here intestinal juices, pancreatic
juices, and bile act on the food. They contain
enzymes that help break down carbohydrates,
proteins, and fats into simple substances the
body can absorb and use.
• Once digestion is complete absorption can take
place.
Leftovers
• Indigestible residue, bile pigments, other
waste, and water travel from the small
intestine to the large intestine. The large
intestine acts as a reservoir. Eventually the
body will excrete these materials in the
feces.
Absorption
• The body can absorb water, ethyl alcohol,
and simple sugars directly from the
stomach. They pass through the stomach
walls into the bloodstream.
• Most absorption takes place in the small
intestine.
• Millions of hair like fingers called villi line
the small intestine. They increase the
absorptive surface by 600 percent.
Metabolism
• Is the chemical processes that take place
in the cells after the body absorbs
nutrients.