Download The Digestive System

The Digestive System
Why do you eat food?
Why do you eat food?
• Because your cells need energy to function
• Because your cells need raw materials to keep
building your body
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Proteins
Carbohydrates
Lipids
Nucleic Acids
What happens to the food when
you eat it?
• It is processed in 4 steps:
1. Ingestion
2. Digestion
3. Absorption
4. Elimination
Ingestion: the art of eating!
• Ingestion is the process of the food entering
the mouth.
• (Ingestion is eating.)
Digestion
• Digestion is the process of breaking food into
small molecules that can be absorbed into the
blood stream later.
• Enzymes are a type of protein that speed up
chemical reactions. Enzymes are found in the
stomach to speed up the rate of digestion.
– Amylase breaks carbohydrates into simpler sugars
– Pepsin helps break proteins into amino acids
– Lipase breaks lipids down
Digestion
• Digestion is the process of breaking food into
small molecules that can be absorbed into the
blood stream later.
• Digestion happens via 2 processes
– Mechanical digestion
– Chemical digestion
Digestion
happens in
the mouth
and
stomach
Digestion happens via 2 processes:
• Mechanical
– Using crushing force to break apart the
food into small molecules
– EXAMPLES: CHEWING &
STOMACH CRUSHING THE FOOD
• Chemical
– Using chemicals to break apart the
food into small molecules
– EXAMPLES: SALIVA IN THE MOUTH AND
HYDROCHLORIC ACID IN THE STOMACH
HCl
Absorption
• Absorption is the process of the food
molecules being absorbed into the blood
stream from the small intestines
small intestines
Elimination
• Elimination is the discarding of waste from
the body.
– Solid is called feces
– Liquid is called urine
Let’s walk through the steps one
more time:
Ingestion Digestion
• Food is ingested through the mouth where it
is chewed (mechanical digestion) and coated
in saliva (chemical digestion).
• When the food is swallowed, it goes through
the esophagus to the stomach so it can be
further digested.
Digestion Absorption
• The food is crushed by muscles in the
stomach (mechanical digestion) and coated in
HCl and enzymes (chemical digestion) until it
is a soupy mixture.
• Then the soupy mixture is pushed into the
small intestine where the food is absorbed
into the blood stream.
Stomach
Small Intestine
Absorption Elimination
• The rest of the mixture is pushed to the large
intestines where the water in the soupy
mixture is absorbed back into the body,
leaving only solid waste.
• The solid waste is pushed through the large
intestines until it is eliminated from the body
through the anus as feces.
Small Intestine
Large Intestines
1. What are the 2 types of
digestion. Gives examples of each.
1. What are the 2 types of
digestion. Gives examples of each.
• Mechanical
– Examples: chewing or the stomach muscles
crushing the food
• Chemical
– Examples: the enzymes in saliva breaking the food
down or the HCl and enzymes in the stomach
breaking down the food.
2. What is pushing the food
through the digestive system?
2. What is pushing the food
through the digestive system?
• Smooth muscles in the digestive organs
contract and relax pushing the food through
the digestive system.
3. Where does digestion start?
3. Where does digestion start?
• Digestion starts in the mouth
– Food is mechanically broken down by teeth
– Food is chemically broken down by enzymes in
saliva
4. Where does absorption take
place?
4. Where does absorption of
nutrients take place?
• Absorption of nutrients into the blood stream
takes place in the small intestine.
5. Why does the body need to reabsorb water in the large
intestines?
5. Why does the body need to reabsorb water in the large
intestines?
• So that the body will not become easily
dehydrated.
6. Where do the enzymes involved
in digestion come from?
6. Where do the enzymes involved
in digestion come from?
• Amylase comes from salivary glands in the
mouth
• Pepsin and lipase come from the pancreas and
are fed into the stomach through ducts
7. What is the correct sequence of
organs in the digestive tract?
7. What is the correct sequence of
organs in the digestive tract?
mouth
esophagus
stomach
small intestine
large intestine
8. Label the parts of the digestive
system.
8. Label the parts of the digestive
system.
esophagus
liver
stomach
gall bladder
pancreas
small intestine
large intestine