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Food’s journey through the . . .
DIGESTIVE SYSTEM
Digestion
▪ Digestion breaks food molecules down into smaller
molecules
▪ It is necessary to make smaller molecules because
these nutrients need to be used by CELLS.
▪ Only small molecules can pass through the cell
membrane and into the cell so it can be used.
▪ EX: We break starch ( a large molecules) down into
glucose (a small molecule that can cross cell
membranes) so our cells can do respiration and
make energy!
Digestion
What are each of the following broken
down into???
▪Proteins →
Amino Acids
▪Starch →
Glucose
▪Lipids → Fatty Acids
▪Carbohydrates → Simple Sugars
Steps of Digestion:
Ingestion → Digestions → Absorption → Excretion
Types of Digestion
▪ Mechanical – physically
breaking food down into
smaller pieces
▫ This creates more surface area, so
enzymes can get to more
molecules
▪ Chemical – use of chemicals
and enzymes to break food into
substances that can be
absorbed
Mouth
▪ Teeth are used for mechanical
digestion to break the food into
smaller pieces, so it can be easily
swallowed.
▪ Saliva contains an enzyme (amylase) used in
chemical digestion, which breaks down starches
into simple sugars
▪ The tongue is your strongest muscle used to
manipulate food during mastication
Esophagus
▪ The tube the food travels
down to get to the stomach
▪ Peristalsis is the motion that pushes the food
down the tube. The tube pinches off above the
food pushing it toward the stomach
▪ You have an epiglottis that covers your
esophagus while you are breathing and covers
your trachea while you are swallowing
▪ This prevents food from “going down the wrong
tube”
Stomach
▪ The stomach
performs
mechanical and
chemical digestion of food.
▪ The stomach secretes a powerful acid (pepsin) that
breaks food down
▪ It also churns mixing the food with the acid and
breaking it down mechanically
▪ Chyme is the mixture of stomach acid (pepsin), broken
down food, and saliva that flows from the stomach into
the small intestine
Duodenum
▪ This is the first section of
the small instestine, where
most of the chemical
digestion of carbohydrates,
lipids, and proteins occurs
▪ Chyme is joined with
enzymes from the liver and
pancreas that reduce
acidity of the chyme and
chemically digest the food
Small Intestine
▪ The small intestine are covered
in little finger like projections
called villi
▪ Villi increase the
surface area of the
small intestine to
increase absorption
of nutrients
▪ The usable nutrients are removed from the chyme
and travel across the villi into the blood vessels that
are inside it
Large Intestine
▪ When the food arrives in the
large intestine it is nutrient free
▪ The large intestine pulls any excess water out of the
remaining indigestible material creating feces
▪ The large intestine is filled with bacteria that help
our digestion process
▪ When the large intestine is not removing enough
water, diarrhea will result
▪ When the large intestine removes too much water,
constipation will occur
Rectum
▪ The rectum will store the
feces until there is enough to pass out of the body
▪ When the rectum is full, you feel the urge to go to
the bathroom
▪ There is a sphincter muscle at the bottom of the
rectum called the anus
▪ This squeezes shut to keep feces in the rectum and
expands to allow it out when passing a stool
Liver,
Pancreas, &
▪Gallbladder
The liver and pancreas secrete
enzymes and digestive fluids that
mix with the chyme in the duodenum
▪ The pancreas secretes a fluid to neutralize the
acidity of the stomach acid
▪ The liver secretes bile, which is
used to break down fatty acids
(lipids)
▪ Bile is stored in the gallbladder
Appendix
▪ Is located near the junction of
the small and large intestine
▪ The appendix is a vestigial organ, which means it
was once used but shrunk in size as it became
less useful
▪ Some organisms use the
appendix to help break down
cellulose in very fibrous
substances (leaves)
Common Diseases
What diseases or problems do you think of when
you think of the digestive system?
▫ Diarrhea
▫ Diverticulitis
▫ Constipation
▫ Ulcerative Colitis
▫ Appendicitis
▫ Hemorrhoids
▫ GERD
▫ Celiac’s
▫ IBS
▫ Lactose
▫ Ulcers
Intolerance
▫ Stomach Ache
▫ Cirrhosis
Diarrhea and Constipation
▪ Diarrhea – too much
fluid in the bowel
movements
▪ Constipation – too
much water being
removed from the
▫ Caused by the large
bowel movements
intestine not removing
enough water
▫ Can be caused by
viruses, bacteria, etc.
▫ Can lead to dehydration
and eventually death
▫ Can be caused by poor
diet or not taking in
enough water
▫ Symptoms can be
alleviated by taking
laxatives
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▪ http://kitses.com/anim
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