Digestion

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Digestion
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DIGESTION

• We will know the nature of the digestive system,
  the organs that form it and their functions.
• Functions Ingest, digest and absorb the food we
  eat
• Take care of the digestive system and maintain
  it.

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How digestion works

• The food we eat is made up of complex sugars,
  complex fats and large proteins.
• These can not be absorbed by the body they way
  they are.
• They have to be digested and turned into their
  simpler form. This way, our organisms can make
  the best use of them.

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• Digestion begins in our mouth, by chewing our
  food. This process brings into use substances
  called enzymes. They accelerate digestion.
  Chewing also increases the production of saliva.
  When food remains in the mouth long enough,
  saliva decomposes the complex sugars due to the
  presence of the enzyme amylase. Saliva is
  produced from the moment that we think of, see,
  or smell food.

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Mouth and Teeth
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• Once we chew our food, it continues through the
  esophagus, a tube formed by a muscle that
  connects the mouth to the stomach.
• Digestion continues there. The stomach is a sack
  that is crushed when empty and extended when it
  contains food.
• The stomach can hold between 3 and 5 liters of
  food.

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• Food exits the stomach into the small intestine.
  When liquid or when containing a lot of sugar,
  food only stays in the stomach a short time, a
  few minutes at most.
• When food contains many proteins and fats, it
  may stay in the stomach for several hours, up to
  4, in fact.
• This is why when you eat a piece of cake, your
  hunger returns in a short while. When you eat ham
  and eggs, for example, you dont feel hungry for
  several hours.

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• The stomach helps digestion because it molds the
  food and produces pepsin, a substance which
  unfolds proteins. Hydrochloric acid (HCl) also
  offers protection by killing bacterias.
• Once in the small intestine, food is finished
  digesting and here, most absorption takes place.

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• The small intestine is formed by a tube 4 to 7
  meters long and 7 centimeters in diameter. It
  absorbs many nutrients because its internal wall
  is lined with tiny hair called cilia.
• Food remains here fro 4 to 5 hours.

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• Digestion is completed thanks to diverse
  substances called enzymes (where have we heard of
  these before?). These enzymes accelerate the
  digestive process. Some of them are produced in
  the intestines, others in the pancreas.

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• The pancreas starts to produce enzymes as the
  food enters the small intestine. The pancreatic
  juices neutralize stomach acids. In addition,
  they contain other enzymes that break down
  polypeptides (long proteins) into shorter chains
  called amino acids.

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• The pancreas also secrets another enzyme called
  lipase. Lipase breaks down triglycerides (fat
  molecules) into monoglycerides and fatty acids.
  Another enzyme is produced by the pancreas,
  amylase (yes, the same one that is produced by
  the salivary glands). It breaks down dietary
  starch into di- and trisaccharides which are
  converted by other enzymes into glucose to supply
  the body with energy.

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• The food we have eaten is now in a form that can
  be absorbed.
• Proteins are broken down into amino acids, fats
  into fatty acids, and complex sugars into simple
  sugars, or monosaccharides (glucose, also called
  dextrose, fructose, galactose, xylose and ribose).

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Where and How Absorption Occurs

• Food once it is broken down( into amino acids,
  fatty acids and simple sugars)is then absorbed by
  the cilia of the intestines and taken to the
  blood that surrounds the walls of the intestinal
  tube. The blood immediately takes them to the
  liver.

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• Some liquids can be absorbed in the stomach, but
  most of them are absorbed In the small intestine
  and the colon.

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Movement of Food in the Intestines

• Since the small intestine has muscle in this
  walls, it has the property to contract, and doing
  so pushes the food forward.
• All the material that is not absorbed, such as
  vegetable, fibers, water, etc. goes into the
  large intestine or Colon.

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Large Intestine or Colon

• The colon is approximately 1.6 meters long and 4
  to 5 centimeters wide.
• The right half absorbs a great amount of water.
• The left half for depositing, where excrement
  advances until it reaches its final destination,
  the Rectum.

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• The lining of the colon contains many tunnels and
  crevices which contain glands that secretes mucus
  that helps bind together these waste material, or
  Feces.
• When the Rectum is full, the nervous impulses are
  awoken and they promote the Defecation

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• Defecation or expulsion of the feces through the
  opening at the end of the rectum called the Anus