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Unit 19: Biology Part 2 Page 43 of 137
and end in the anus; moving in a seven feet long, if it were spread
wave called peristalsis. Peristalsis out it would cover a basketball
is the name of the movement of court!
the muscle contractions moving
the food through the tube. 1. The duodenum. The
duodenum is the first part of
Mouth to Stomach the small intestine. In the
duodenum the food from the
Digestion begins in the mouth. In stomach is further digested
the mouth, the teeth digest food (chemically). Some of the
mechanically, and the saliva chemicals are secreted from
digests starches chemically. And so the duodenum itself, others
begins the journey. are secreted from the liver
and pancreas.
After the mouth, the food travels 2. The jejunum. Most nutrients
to the stomach through a narrow are absorbed into the body at
tube called the esophagus. The this second part of the small
esophagus moves the ball of intestine. The nutrients are
chewed and partially digested food absorbed through tiny blood
via peristalsis into the stomach. vessels.
3. The ileum. Here nutrients
Once in the stomach, the food is are also absorbed into the
further chemically digested. The blood stream. What is not
protein is digested with the absorbed in the ileum is
enzyme pepsin. Pepsin, along with passed as waste through the
other chemicals such as large intestine.
hydrochloric acid (HCl) chemically
digests the food. Water, salts, and
simple sugars are absorbed
through the walls of the stomach.
The rest of the nutrients are
absorbed after exiting the
stomach.
The small intestine Figure 16 The intestines.
The small intestine is about 7ft
long in adults and is composed of
three parts. Even though it’s only
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