Over the years scientists
have worked to unlock the once mysterious process of how humans digest
food. Some of the approaches can even be used by you to discover what
happens in the digestive tract!
do we learn about the different parts of the digestive system?
When we dissect a dead animal, we can see the different parts along the
tract that begins in the mouth and ends in the anus. See pictures
The cells can be seen by making microscope slides.
could we see where digestion begins?
How would you find out if saliva has any digestion function? A quick way to find out is to compare a
piece of steak (which has a lot of protein) and a cracker (which has a
lot of starches). Place the meat in your mouth and do
not chew it for about 2 minutes. What happens? You should discover that the
steak keeps its shape. Next, place the cracker in your mouth without chewing
it for about two minutes. You should notice that the cracker becomes soft in your mouth and
you may even taste something sweet. This is because the cracker is composed
of carbohydrates, which saliva is able to digest at least partly. The
carbohydrates in the cracker begin to be broken down into individual
glucose molecules by an enzyme in your saliva. This enzyme only breaks
down carbohydrates, not proteins. Since the steak was mostly composed of
proteins, it did not start breaking down like the cracker.
do we know what goes on in our stomach?
stomach contains acids that turn most of your food into a liquid. Have
you ever been sick and felt a burn in the back of your throat after vomiting?
If you have, then you have experienced the power of the acids in your
stomach. Stomach secretions also contain strong enzymes.
The digestive functions of the stomach were discovered during an experiment
performed by Doctor Beaumont. In his experiment, Doctor Beaumont
tested the digestive power of stomach fluids through a "fistula"
(see the graphic on the right) that connected the stomach to the patient's
skin. Doctor Beaumont tied food to a string, poked it through the
fistula, and pulled it back out at varying times to see what had happened
to the food. He observed that the food had changed, varying with
the amount of time spent in the stomach and the nature of the food itself.
One of the major things that was noticed by Doctor Beaumont is that proteins
were especially degraded by the acids of the stomach. See Story
Time for more.
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