Lab 3045
The Monogastric Digestive System
ACTIVITY OBJECTIVES
Students will thoroughly investigate a monogastric digestive system identify organs and
describing their functions.
PURPOSE/OVERVIEW
This lab is designed to help students understand the monogastric digestive system and to
begin to make comparisons between monogastric and polygastric systems.
PRELAB
Review the passage of food through a monogastric digestive system and define the
following terms: esophagus, liver, gall bladder, stomach, small & large intestine, cecum,
rectum, anus, pancreas, villi, and appendix.
LAB BACKGROUND
The stomach in a monogastric digestive system has a single compartment. Monogastric
animals do not ruminate (regurgitate and re-chew food). Examples of animals that do not
ruminate are humans, pigs, bears, cats.
MATERIALS
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Digestive tract or fetal pig Paper
Sharp knife Dissecting Microscope
Pins Reference Materials with pictures
Labels
PROCEDURE
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Lay out the digestive system on table or dissecting tray so all structures can be
easily seen. Locate and label, with pins, the following parts indicated by bold face
type.
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Find the dark, red-brown organ. This is the liver. Notice that the liver is divided
into distinct lobes.
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Raise the right lobe of the liver. Observe the gall bladder, a small greenish sac
embedded in the underside of this lobe.
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Immediately under the left lobes of the liver lies the stomach. Trace the intestine
from the stomach toward the posterior, until it joins the colon, or large intestine.
The smaller tubing is the small intestine, while the larger tubing is the large
intestine. Where the small intestine and the large intestine join, there is a pouch,
called the cecum. In humans, the tip of this pouch is the appendix. Trace the
colon toward the posterior. Just before it reaches the anus, there is a slight
enlargement called the rectum.
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The pancreas, a small, pink-ish, grainy organ, is also part of the digestive system.
It lies just under the stomach, inside the bed made by the first section of intestine.
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Remove a 3 cm section of the small intestine and cut it lengthwise. Then wash
and examine its lining under the dissecting microscope. Describe its appearance in
the observation section. The projections you see are called villi.
OBSERVATIONS
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Draw the digestive system as you have observed it. Label the parts listed in bold
face type.
Describe or draw the lining of the small intestine.
CONCLUSION/ANALYSIS
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Give the name of the proper organ after reading the function of the organ in the
statements below.
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Controls passage of food from stomach to small intestine:
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Site of chemical digestion and absorption of food:
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Stores bile:
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Extension of large intestine that is vestigial in humans
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Storage of undigested food physical mixing of food
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What is the function of the liver?
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What purpose do villi serve? How does their situation improve their function?
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How is the pigs digestive system similar to humans?
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What purpose does the digestive system serve?