Physical and
Chemical
Changes in
the
Digestive
System Notes
EQ: What type of change
occurs at each of the 7
main digestive organs?
Real Life Video of the
Digestive System

Inside the System
Length: 5 min and 7 seconds
You have to put this slide into slide show mode to click on
the link shown.
You will need headphones for this.
There is nothing you need to write down during the video.
Color code
the organs
in the main
digestive
tract.
Your colors do
not need to match
these.
4 Functions of the Digestive System
Highlight the 4 functions
1. Ingestion = Food enters the mouth
1.
2. Digestion = Process that
2.
breaks food down into small
molecules
Digestion
a) Mechanical (physical) digestion:
Changes size and shape only
b) Chemical digestion:
Breaks down large food molecules
into NEW smaller molecules
(Ex: Carbohydrates  Glucose)
3.
3.
Absorption =
Small molecules of food are absorbed by
the villi in the small intestine and are
transferred to the blood to be delivered to
the body’s cells.
4.
4. Elimination =
Wastes made of
unabsorbed molecules
are removed from the
body.
Absorption
Elimination
Read Only
Click to watch villi absorbtion
Absorption

villi
This shows how large
molecules like starches
must be broken down
into smaller sugar
molecules. These
molecules then pass
through the villi which
are the finger-like
projections in the small
intestines that absorb
the nutrients into the
blood.
Write the title shown below in blue. All physical changes that occur in the
digestive system will be also be written in blue to color code the notes.
Physical/ Mechanical Changes
• The APPEARANCE of the substance alters
(changes) NOT their chemical composition!
– Change in size or shape
– Change in the state of matter (solid, liquid, gas)
Write the title shown below in red. All chemical changes that occur in the
digestive system will be also be written in red to color code the notes.
Chemical Changes
• These changes alter the substance so that a
new substance with NEW properties appears
and is NOT reversible:
• Unexpected color change or odor
• Release of heat, light, or sound
• Produces gas (bubbles), or forms a solid substance
7 Major Organs of the Digestive Tract
1. Mouth
Write this section title and
draw a box around it to make
it stand out in your notes.
o The teeth mechanically tear, rip, and
grind the food into smaller pieces.
o The tongue pushes the food towards
the teeth to be chewed.
o Enzymes in the saliva chemically digests
food.
o When swallowing, the epiglottis (a small
flap of tissue) automatically closes over
the trachea (windpipe) to avoid food
“going down the wrong tube”
Red shows passage of air
Green shows passage of food
Put the PPT into slide show mode to
view the above animation
Enzyme: substance that speeds up the breakdown of food
by causing a chemical change in which a new substance is
created.
• Anywhere in the digestive system that a chemical change
takes place enzymes are at work.
Draw and label everything shown in this picture.
Carbohydrate
Simple Sugar
Creation of new substance =
chemical change
(Starch)
Read Only
Digestive
enzymes
Starch breaking down
into smaller sugars
Glucose molecules
2. Esophagus
Peristalsis (rhythmic
smooth muscular
contractions) squeezes the
bolus (a mass of chewed
food) downward from the
mouth into the stomach.
3. Stomach
o The stomach is a smooth
muscle that contracts and
relaxes through peristalsis
which squeezes and churns
(mixes) the bolus breaking
down the size of the ingested
materials
o Stomach acid (hydrochloric
acid) contains enzymes which
chemically break the bolus
down further forming chyme.
What happens to food inside the stomach?
Read Only
Accessory Organs- organs that help
digestion by producing chemicals but do
not actually touch the food.
1. Liver: Bile (chemical digestive
juice) is produced here (Bile
breaks down fats like dish
detergent breaks down grease.)
2. Gall Bladder: Bile is stored here
until released into the beginning
of the small intestine.
3. Pancreas: Produces pancreatic
juices that are released into the
beginning of the small intestine
to break down proteins,
starches, and fats.
The bile and pancreatic
juice are secreted into the
very beginning of the
small intestine which is
called the Duodenum.
Draw a bubble around the notes about Accessory
Organs as shown below.
Then, lightly shade the background of that bubble
with your pencil.
The reason it is being shaded is to make it stand out; this is because these
organs are not part of the main digestive tract which is what the rest of your
notes are about. On the other hand, they play a role in digestion in the small
intestine which is why we are writing those notes in that location.
Click HERE for enzyme video
You will need headphones.
The PPT must be in full screen Slide Shown Mode to access the link above.
4. Small Intestine
(Longest digestive organ:20 feet long!)
o The bile and pancreatic juice are secreted into the very
beginning of the small intestine (the Duodenum.) These
digestive juices are the final digestive stage in breaking
down remaining large molecules.
o Nutrients from the chyme (digested food) are absorbed
through the villi and enter into the bloodstream. The
blood then delivers the nutrients to the body’s cells.
5. Large Intestine (aka: colon)
o Since all nutrients were absorbed in the small intestine,
the remaining material is called feces, but these wastes
are very watery.
o The feces spend 18–24 hours in the large intestine.
During this time, most of the water is absorbed into the
blood stream.
o Materials not absorbed form into solid waste.
appendix
This box is READ ONLY:
Feces is composed of dead bacteria, some fat and protein, undigested food, dried out parts of digestive
juices, and old intestinal cells.
6. Rectum
Solid waste passes into the
rectum which stores the solid
waste until it is ready to be
eliminated.
7. Anus
The anus is the opening
through which solid waste is
expelled out the body.
Did you notice….?
Read Only
“Food” is not called “food” the entire time it is in your
body. Since physical and chemical changes are
happening to the food throughout the digestive
system, its name changes as it travels.
Chewed food, once swallowed, becomes a bolus. The
bolus becomes chyme when it mixes with the stomach
acid in the stomach. When the nutrients are absorbed
from the chyme in the small intestine, it then becomes
watery feces. The watery feces dries out in the large
intestines forming solid feces.
Saliva dissolves starch into sugars
Teeth chew food
Peristalsis
pushes the
bolus down
the esophagus
Review: READ ONLY
Contractions of the stomach muscles
squeeze the chyme
Stomach acid chemically breaks down
the chyme
Water is
squeezed from
the large
intestine to
solidify the
waste
Digestive juices from the accessory
organs (liver, gallbladder, and pancreas)
are released into the beginning of the
small intestine
Nutrients are absorbed by
the villi in the small
intestine
The solid waste is stored in
the rectum
The solid waste is released
through the anus
ASSIGNMENT
Create a double bubble comparing physical digestion
and chemical digestion.
Physical
Digestion
Chemical
Digestion
This is NOT the exact
number of bubbles you
should have. This
picture is just to
remind you what a
double bubble looks
like.
Do NOT pre-draw the
bubbles and then fill
them in. Instead, draw
a new bubble for each
new detail you come
up with.