Transcript Digestion: The 24-Hour Food Factory

Digestion:
The 24-Hour Food Factory
Digestion: A two-part process
• Mechanical digestion takes place in your mouth
and your stomach. Your teeth break food into
small pieces that you can swallow without
choking. In your stomach, a churning action
continues to break food into smaller particles.
• Chemical digestion occurs at every point in the
digestive tract where enzymes and other
substances such as hydrochloric acid and bile
dissolve food, releasing the nutrients inside.
Understanding How Your Body
Digests Food
• Eyes and Nose- when you see an appetizing
food, you experience a conditioned response
(your thoughts tell your digestive organs to get
ready for action)….when you smell an
appetizing food, the receptors cells
communicate with your brain which sends
messages to your mouth and digestive tract.
The sight and smell of food makes your mouth
water and your stomach contract in anticipatory
hunger pangs.
Mouth
• The mouth- your teeth chew and grind the food
so that you can swallow without choking and you
break off the indigestible wrapper of fibers
surrounding the edible parts of some foods
(fruits) so that your digestive enzymes can get to
the nutrients inside.
~Salivary glands under the tongue discreet saliva
which moistens and compacts foods, and
provides amylases, enzymes that start the
digestion of complex carbohydrates (cracker).
Turning starches into sugars
• Put a small piece of unsalted, plain cracker on
your tongue.
• Close your mouth and let the cracker sit on your
tongue for a few minutes.
Do you taste a sudden, slight sweetness?
That is the salivary enzymes breaking a long,
complex starch molecule into its component
parts (sugars).
• Okay, you can swallow now. The rest of the
digestion of the starch takes place further down,
in your small intestine.
Stomach
• The stomach- your
stomach is circled with
strong muscles whose
rhythmic contractionscalled peristalsis.’- move
food smartly along and
churn your stomach into a
sort of food processor
that mechanically breaks
down food. The stomach
wall secretes stomach
juices to help break down
the food.
Small Intestine
• Open your hand and put it flat against your belly button, with your
thumb pointing up to your waist and your pinkie pointing down…your
hand is now covering most of the small space into which your 20
foot long small intestine is neatly coiled.
• Chyme spills from stomach and more gastric juices are
released…while these chemicals are working, contractions in the
small intestine continue to move the food down the tube so the body
can absorb nutrients into the cells in the walls of the intestine
• Nutrients are absorbed by according to how fast they are broke
down.
~fats take the longest to break down…that is why a high fat meal
(hamburger) keeps you full longer than a meal of low fat carbs
(plain tossed salad)
The Large Intestine
• After every useful, digestible ingredient other
than water has been rung out of your food, the
rest- indigestible waste such as fiber- moves into
the top of your lg intestine known as your colon.
The colon absorbs the water and squeezes the
remaining matter into compact bundles know as
feces.
• The feces pass down your rectum and out
through your anus.
• Digestion is done!