Download DIGESTIVE SYSTEM READING

DIGESTIVE SYSTEM READING
INTRODUCTION
You will be learning about the rat digestive system through several means: reading, dissecting, answering
questions, and coloring.
COLORING
Color the diagrams of the rat and human digestive systems.
DISSECTING
The mandibular salivary glands lay on either side of the trachea, just below the mandible. Locate these
glands on your rat but note that you have moved them aside or even mistakenly removed them in an effort to
skin the rat.
Open up the digestive cavity by making a cut with your scissors from just anterior to the genitalia, up to the
posterior tip of the pectoralis minor muscle. As you open up the cavity you will note a prominent sheet
covering the stomach called the greater omentum. This sheet is often accompanied by globs of fat and is
sometimes referred to as a “beer belly” on humans. DO NOT cut out the abdominal muscles but rather flap
these muscles to either side. You will need the abdominal muscles to review for the lab portion of the final
test.
Find the esophagus as it passes through the diaphragm wall. Below the diaphragm is a large, reddish
structure, the liver. Follow the digestive system carefully and progressively from esophagus to stomach to
small intestine to cecum to large intestine to rectum to anus. The slender spleen lies alongside the
stomach.
Once you have identified each of the structures in the rat, learn the structures even better. Carefully remove
the digestive system from the esophagus, just as it passes through the diaphragm, down to the end of the
large intestine. Lay the digestive system out on a paper towel. The small intestine will be tightly wound
with a clear sheet called the mesentery. Snip the mesentery such that you can lay out the small intestine
more fully. Re-identify each of the structures a second time. Complete the flowchart table on the digestive
system worksheet.
Now look closely at the stomach. Slit the stomach open longitudinally. Remove and dispose of the food
that was in the process of being digested. Rinse the stomach out under the faucet. Examine the interior of
the stomach. The stomach is divided into three sections: the forestomach (just after the esophagus), the
fundic portion (large middle portion of the stomach), and the pyloric region (the restricted region just
before the stomach passes into the small intestine). Find the pyloric valve at the end of the stomach just
before the small intestine. Draw and label the stomach of the rat on the digestive system worksheet.
(OVER PLEASE)
Take a closer look at the small intestine. Cut out a small portion of the small intestine. DO NOT cut the
intestine in half. Similar to the stomach, remove the food and rinse out the intestine. Place the intestine on
a Petri dish and examine under a stereomicroscope. Note the small, finger-like villi that cover the interior of
the intestine. Draw the small intestine of the rat and label the villi on the digestive system worksheet.
cut
Take a closer look at the large intestine. Cut out a small portion of the large intestine. DO NOT cut the
intestine in half. Similar to the stomach, remove the food and rinse out the intestine. Place the intestine on
a Petri dish and examine under a stereomicroscope. Note the pocket-like haustra of the large intestine.
Draw the large intestine of the rat and label the haustra on the digestive system worksheet.
DO NOT throw out the digestive system. Place the system back in the rat.