The Small Intestine

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The Small Intestine

• How does it work? What does it do? Why is it
  important to our body?

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General Description

• The small intestine (say in-test-in) is a long
  tube that's 1 1/2 inches to 2 inches around, and
  it's packed inside you beneath the stomach. If
  you stretched out your small intestine, it would
  be about 22 feet long - that's like 22 notebooks
  lined up end to end, all in a row! The small
  intestine has the important job of breaking down
  the food mixture so your body can absorb all the
  nutrients it needs from food - vitamins,
  minerals, proteins, carbohydrates, and fats. The
  meatball topping on your pizza is full of
  protein, but only the small intestine can unleash
  its power for you - those meatballs don't go
  directly into your body's tissues to give you
  energy.

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Functions of The Small Intestine

• Aid in digestion- helping along the way of
  processing food
• Hormone secretion- how it uses hormones to help
  digest food
• Nutrient absorption- what it takes in and were it
  goes

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Aid in Digestion

• Over a period of three to six hours, peristalsis
  moves chyme through the duodenum into the next
  portion of the small intestine.
• During this time, the liver secretes bile into
  the small intestine through the bile duct. Bile
  breaks large fat globules into small droplets,
  which enzymes in the small intestine can act
  upon.

• Pancreatic juice, secreted by the pancreas,
  enters the small intestine through the pancreatic
  duct. Pancreatic juice contains enzymes that
  break down sugars and starches into simple
  sugars, fats into fatty acids and glycerol, and
  proteins into amino acids.
• Glands in the intestinal walls secrete additional
  enzymes that break down starches and complex
  sugars into nutrients that the intestine absorbs.
  

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Secretion of Hormones

• The mucous membranes of the small intestine
  secrete hormones that stimulate secretion of
  digestive juices from the pancreas.

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Nutrient Absorption

• The small intestines capacity for absorption is
  increased by millions of fingerlike projections
  called villi, which line the inner walls of the
  small intestine. Each villus is about 0.5 to 1.5
  mm (0.02 to 0.06 in) long and covered with a
  single layer of cells. Even tinier fingerlike
  projections called microvilli cover the cell
  surfaces. This combination of villi and
  microvilli increases the surface area of the
  small intestines lining by about 150 times,
  multiplying its capacity for absorption. Beneath
  the villis single layer of cells are capillaries
  (tiny vessels) of the bloodstream and the
  lymphatic system. These capillaries allow
  nutrients produced by digestion to travel to the
  cells of the body. Simple sugars and amino acids
  pass through the capillaries to enter the
  bloodstream. Fatty acids and glycerol pass
  through to the lymphatic system.

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1 Small Piece of a Large Puzzle

• The small intestine is but one piece of your
  digestive system. It all starts at your mouth and
  ends well you know where Im going with that.
  Almost all of the organs in your body play some
  part in the digestive process, most produce or
  store enzymes or digestive substances.

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Hot Spots to Learn

• http//www.innerbody.com
• http//www.enchantedlearning.com/subjects/anatomy/
  digestive/
• Search msn.com key words small intestine
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