The Digestive System
What is digestion?
The process by which your body breaks down food, and
the nutrients in food, into simpler substances.
Where does
digestion start?
Mouth
Mastication, or chewing, starts the
digestive process.
Odors and taste from food activate
salivary glands and produce
saliva.
Saliva is 99% water, but it also
has a few chemicals in it.
One chemical present in saliva is
the enzyme salivary amylase.
Salivary amylase starts the
breakdown of starches.
Define Enzyme
A substance produced by a living organism that acts as a catalyst
to bring about a specific biochemical reactions.
Define Catalyst
A substance that increases the rate of a chemical reaction
without itself undergoing any permanent chemical change.
Esophagus
As you swallow, food passes from
the mouth to the stomach
through the esophagus.
A flap of skin called the epiglottis
closes to keep food out of the
trachea (windpipe).
A series of squeezing actions by
the muscles in the esophagus,
known as peristalsis, help move
food through the tube.
Stomach
The stomach produces gastric juices
that contain hydrochloric acid (HCl),
digestive enzymes, and mucus.
When mixed with food, the mixture is
called chyme.
The mucus in the stomach helps soften
and lubricate food. It also helps
protect the stomach from its strong
acidic juices (almost as strong as
battery acid).
Protein digestion starts in the stomach.
The major enzyme that helps break
down protein is pepsin.
In what order do foods leave the stomach?
Food remains in the stomach for 2-3 hours.
Then is starts to leave in this order:
1. Liquids
2. Carbohydrates
3. Proteins
4. Fats
In what order would this meal digest?
A turkey sandwich (bread, turkey, tomato,
lettuce, mayonnaise)
A glass of milk
An orange
Small Intestine
The small intestine has 3 different
sections:
duodenum: 12 inches
jejunum: 4 feet
ileum: 5 feet
It takes about 5-14 hours for food to
travel from the mouth through the
small intestine.
Peristalsis moves food through the
small intestine.
3 organs aid in digestion in the small intestine.
1. Pancreas: helps create a less acidic
environment for digestion in the small
intestine. It secretes bicarbonate (base),
which neutralizes the HCl (acid) coming from
the stomach. The pancreas also produces
digestive enzymes that break down proteins,
carbs, and fats into their most basic parts.
2. Liver: produces the digestive juice called bile.
Bile aids in fat digestion by helping disperse
the fat in the water-based digestive fluids.
This gives enzymes access to the fat to help
break it down.
3. Gallbladder: Bile is stored in the gallbladder
until it is needed.
What is absorption?
The passage of nutrients from digestive tract into the:
Circulatory System
Lymphatic System
Absorption
The inside of the small intestine is about 600 times
larger than a smooth surface because of the
thousands of folds.
These folds are covered with villi.
Each villus is covered with microvilli which are
microscopic hairs that help catch nutrient particles.
Water soluble nutrients are absorbed into the
bloodstream through the capillaries--the blood
vessels in the villi.
Fat soluble nutrients are absorbed into the lymphatic
system through the lymph vessels in the villi,
Large
Intestine/Colon
Very little digestion occurs in the colon.
Chyme is very liquid when it enters and
stays about 1-3 days before elimination.
During this time, water is absorbed
through the walls of the colon and useful
bacteria work on fiber as well as help
manufacture small amounts of vitamins.
Solid wastes are called feces and include:
mucus, bile pigments, fiber, sloughed off
cells from the lining of the colon, and
water.
The end of the large intestine is called the
rectum. This is we're feces are collected
Metabolism
All the chemical changes that occur as cells
produce energy and materials needed to sustain
life.
Through metabolism, cells convert some
nutrients into energy. The body stores this
energy as ATP (adenosine triphosphate). ATP
is the source of immediate energy found in
muscle tissue.
Factors Affecting Digestion and Absorption
Eating Habits
Eat a variety of foods to
insure proper digestion.
Also include lots of fresh
fruits, vegetables, and
whole grain products.
These are high in fiber
and help strengthen
intestinal muscles.
Take your time when you eat.
Eating too quickly can put
stress on your digestive
system and it can no
longer function most
Emotions
Fear, anger, and
tension can
lead to
digestive
difficulties.
Food Allergies and Intolerances
Allergy - reaction from body’s immune
system. The body produces
antibodies to protect the body from
foreign materials. Symptoms of an
allergic reaction are vomiting,
stomach pain, intestinal stress, skin
rashes, swelling, and breathing
problems.
Intolerance - usually requires a larger
amount of food. They are caused by
deficiencies or reactions in the
digestive tract. Symptoms can be
similar to allergies,but they can also
include elevated blood pressure,
Physical Activity
Stimulates a healthy
appetite
Strengthens the
muscles of internal
organs
Move food brought the
GI tract.
Reduces stress and
adds to overall
sense of wellbeing.
Digestive
Disorders
Explain what the
disorder is and how
it is treated or
prevented.