2. STATION 14: The small intestine
The body’s major digestive organ. Begins at the pyloric sphincter of the
stomach, coils through the central and lower part of the abdominal
cavity, and eventually opens into the large intestine. It is @ 20 feet long!
Subdivisions of the Small Intestines
1. Duodenum – attached to stomach, where most
chemical digestion using enzymes takes place.
2. Jejunum – middle portion, designed to absorb
carbohydrates, proteins and water.
3. Ileum – final twisted portion that absorbs vitamin
B12, bile salts, and any products of digestion that
were not absorbed by the jejunum.
3. STATION 14: The small intestine
It is called the “small” intestine because it is
smaller in diameter, but it has a LARGE job!
FUNCTIONS: The small intestine uses enzymes
from the pancreas and bile produced in the liver
to further break down nutrients. The role of the
small intestine is to absorb nutrients.
The only absorption
that occurs in the stomach
is of alcohol, caffeine, and
aspirin (these are absorbed by
the stomach lining directly into
the blood)…YIKES!
Villi are
finger-shaped folded
projections from the wall of
the small intestine where nutrients are
transferred to the bloodstream.
Villi also increase the surface area of the
“SI” so that it can absorb
more nutrients.
Your “stomach growling” could actually
be your stomach or your small intestine
as it digests food. As the food breaks
down, gases are released and may make
a “gurgling” sound.
4. STATION 14: The small intestine
The small intestine is made of smooth muscle
that contracts to push food along during
peristalsis, which occurs in slow intervals in the
small intestine.
The small intestine
can process 2
gallons of food and
liquid every day!
SECRETIONS:
• Alkaline mucus
• Secretin (inhibits release of gastric juice for acidic
chyme
• Cholecystokinin (CCK) causes gall bladder to release
bile
• Intestinal Juice (maltase, sucrase, lactase, pepidase)
In addition to
peristalsis, the small
intestine performs
muscle contractions
known as
segmentation, in
which the chyme
(digested food) is
moved back and
forth in short
segments.
