Veterinary Medical Applications
Lesson Title: Digestion
TEKS Addressed in Lesson:
130.6.
(c)(4)(A) Analyze veterinary terms to discover their meaning and recognize common Greek and Latin
prefixes, suffixes, and roots
(c)(4)(B) Develop appropriate use of directional anatomical terms
(c)(4)(C)Identify anatomical structures of animals
(c)(4)(D) Describe the major body systems by using appropriate medical terminology
(c)(4)(E) Recognize, pronounce, spell, and define medical terms relating to diagnosis, pathology, and
treatment of animals
(c)(6) (A) Identify the parts of the skeletal, muscular, respiratory, circulatory, digestive, endocrine, and
nervous systems
(c)(6) (B) Describe the functions of the skeletal, muscular, respiratory, circulatory, digestive, endocrine,
and nervous systems
(c)(6) (D) Use medical terminology to describe normal animal behavior and vital signs compared to sick
animals
Lesson Objectives:
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Describe the functions of the major parts of the digestive systems.
Analyze kinds of feed in relation to animal digestion systems.
Explain the role essential nutrients play in animal health and be able to determine the source of
each of the essential nutrients
Be able to define nutrition and explain its importance in maintaining animal health.
Identify the six basic nutrients and their function in maintaining animal health.
Compare and contrast the ruminant and non ruminant digestive systems.
Recognize the importance of guaranteed analysis in selecting animal feed.
Key Terms/Vocabulary
Bile- bitter greenish-brown alkaline fluid that aids digestion and is secreted by the liver and stored in the
gallbladder
Cecum- a pouch connected to the junction of the small and large intestines
Chyme- the pulpy acidic fluid that passes from the stomach to the small intestine, consisting of gastric
juices and partly digested food
Cud- partially digested food returned from the first stomach of ruminants to the mouth for further
chewing
Digestion- the process of breaking down food by mechanical and enzymatic action in the alimentary
canal into substances that can be used by the body
Enzyme- a substance produced by a living organism that acts as a catalyst to bring about a specific
biochemical reaction
Eructated- Belching (also known as burping or eructation) involves the release of gas from the digestive
tract through the mouth
Esophagus- the part of the alimentary canal that connects the throat to the stomach; the gullet
Gallbladder- the small sac-shaped organ beneath the liver, in which bile is stored after secretion by the
liver and before release into the intestine
Liver- large lobed glandular organ in the abdomen of vertebrates, involved in many metabolic processes
Monogastric- A monogastric organism has a simple single-chambered stomach, whereas ruminants have
a four-chambered complex stomach. Examples of monogastric animals include humans, pigs, dogs, and
cats. Horses and rabbits have modified monogastric digestive systems, and are called hindgut
fermenters
Pancreas- a large gland behind the stomach that secretes digestive enzymes into the duodenum
Pancreatic amylase- Amylase is an enzyme that breaks starch down into sugar
Saliva- watery liquid secreted into the mouth by glands, providing lubrication for chewing and
swallowing, and aiding digestion
Interest Approach/Anticipatory Set
Have students discuss the differences between animals like cattle and dogs…sharp teeth, hooves, etc..
Then introduce these physical characteristics as traits or “clues” as to how the animal digests it’s food.
At this point, show the students outlines of the monogastric, ruminant, and the avian digestive tracts.
Ask them to note the differences and to hypothesize why the differences are present.
Teaching Plan and Strategy Presentation of New Material
Explain and give examples of monograstic animals, ruminants and modified monogastric animals. In
addition, explain the process of digestion for each and how and why their anatomy differs, for example,
because chickens do not have teeth, they have a gizzard, and because ruminants eat roughages, they
have to chew their food twice.
Go over Nutrition/Digestion Presentation that goes over the following information:
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Breaking down feed into simple substances that can be absorbed by the body.
Absorption is taking the digested parts of the feed into the bloodstream.
The digestive system consists of the parts of the body involved in chewing and digesting feed.
This system also moves the digested feed through the animal’s body and absorbs the products
of digestion.
Different species of animals are better able to digest certain types of feeds better than others.
This difference occurs due to the various types of digestive systems found in animals.
There are four basic types of digestive systems: monogastric (simple), avian, ruminants
(polygastric), and pseudo-ruminants. A. A monogastric digestive system has a simple stomach.
The stomach is a muscular organ that stores ingested feed and moves it into the small intestine.
The stomach secretes acid. Animals with this type of digestive system are better adapted to the
use of concentrated feeds, such as grains, than the use of large quantities of roughages.
Examples of monogastric animals are dogs, cats, swine and humans.
The avian digestive system is found in poultry and other birds. This system differs greatly from
any other type. Since birds have no teeth, there is no chewing. The esophagus empties directly
into the crop. The crop is where the food is stored and soaked. From the crop the food makes it
way to the gizzard. The gizzard is a very muscular organ, which normally contains stones or grit
which functions like teeth to grind the food. Digestion in the avian system is very rapid.
The polygastric or ruminant digestive system has a large stomach divided into compartments.
The largest section of the stomach is the rumen. The rumen contains bacteria and other
microbes that promote fermentation. The rumen is the first compartment of the stomach that
food enters. This system is designed for food to be ingested, eructated (belched up), chewed,
and swallowed again. The reticulum is the second segment of the stomach. Next is the omasum,
followed by the abomasum. The omasum is a small compartment that acts as a filter of
materials for the abomasum. The abomasum secretes gastric juices that kill the microbes that
have passed with the food materials from the rumen. The juices and other substances in the
abomasum digest the microbes. The polygastric system uses feed high in fiber. Thus, these
animals make good use of roughage. Some examples of polygastric animals are cattle, sheep,
and goats.
Some of the major parts of the digestive system and their functions are:
A. Mouth and esophagus—the chewing action of the mouth and teeth breaks, cuts, and tears up the
feed. This increases the surface area of the feed particles which aids in the chewing and swallowing
process.
B. Ruminant stomach—the four parts of the ruminant stomach are rumen, reticulum, omasum, and
abomasum. Ruminant animals typically eat rapidly. They do not chew much of their food before
swallowing. The solid part of food goes into the rumen. The liquid part goes into reticulum, then the
omasum and on into the abomasum.
C. Monogastric stomach—when feed enters the stomach of monogastrics or the abomasum of
ruminants, gastric juices begin to flow. The fluid comes from glands in the wall of the stomach.
D. Small intestine—the partly digested feed that leaves the stomach enters the small intestine. It is an
acid, semi-fluid, gray, pulpy mass. This material is called chyme.
E. Cecum—the cecum or is located where the small intestine joins the large intestine. It is a small organ
and has little function in most animals, except pseudo ruminants. In these animals, roughage feeds are
digested by bacterial action in the cecum.
F. Large intestine—the main function of this organ is to absorb water. Material not digested and
absorbed in the small intestine passes into the large intestine. Feed materials that are not digested or
absorbed are called feces.
Substances that assist in the breakdown of food stuff:
1. In the small intestine, the chyme is mixed with three digestive juices: pancreatic juices, bile, and
intestinal juice.
2. Pancreatic juice secreted by the pancreas, contains the enzymes trypsin, pancreatic amylase,
pancreatic lipase, and maltase. Trypsin breaks down proteins not broken down by pepsin.
3. Bile is a yellowish-green, alkaline, bitter liquid produced in the liver. Bile is stored in the gall bladder in
all animals except horses. Bile aids in the digestion of fats and fatty acids. It also aids in the action of the
enzyme lipase.
4. Glands in the walls of the small intestine produce intestinal juice. This fluid contains peptidase,
sucrose, maltase, and lactase, all enzymes used in digestion. Proteases and peptones are broken down
by peptidase into amino acids. Starches and sugars are broken down by sucrase, maltase, and lactase
into the simple sugars, glucose, fructose, and GA lactose.
Activity/Application/Student Engagement/Laboratory
-Discussion Question: What are the essential nutrients for animals? What do they do? Where do they get
these nutrients? Have students use computers or personal devices to look up the essential nutrients,
their function in the body and how animals obtain these nutrients. (A premade chart that students can
fill in is very helpful for this exercise)
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Water-found in every cell of the body, necessary for all bodily functions
Protein-found in every cell of the body, provides maintenance of body tissues, is a major source
of energy, assists in the creation of some hormones in the body, transportation and storage of
molecules, anitbodies that prevent diseases
Lipids- energy storage
Carbohydrates-energy storage-Carbohydrates spare protein so that protein can concentrate on
building, repairing, and maintaining body tissues instead of being used up as an energy source
Vitamins-Provide structural material to bones and connective tissue; Act as catalysts involved in
the numerous physiological processes such as DNA replication, digestion, immune function,
endocrine synthesis, neurological activity, energy storage and release, muscle contraction and
numerous other functions
Minerals-specialized jobs in the animal body
-Have students color and label the handouts of the ruminant non-ruminant digestive systems.
Digestion Simulation Lab:
Materials List for Each Demonstration:
1 graham cracker
1 Ziploc bag (quart size)
2 nylon knee-high hose (of different colors); can also cut regular host to right size
½ of a banana
1 small cup filled with water
Tray to catch the juices
Flexible rubber tube approximately 18 inches long (optional)
Activity Summary:
This is a demonstration to reinforce the students’ understanding of the digestive process. This can
strictly be a demonstration performed by the teacher or the teacher could have the students help with
each step of the digestive process. (if funds and time allow, you can break students up into groups of 34 and have each group do their own demonstration)
Activity Introduction / Motivation:
Tell the students that they are going to see digestion in progress. If you are allowed to give food out in
class, give students a small piece of graham cracker and then launch into the demonstration as they are
eating. This is not necessary, but it helps them visualize the process.
Instructions:
1. Tell the students that you are hungry and you have decided to have a graham cracker for a snack.
Place a graham cracker in a Ziploc bag and ask the students what they think happens when they first
start to eat anything.
Answer: When they first start to eat, they bite into the food or put it in their mouth.
2. Now have one student come up and crunch the graham cracker with the Ziploc bag closed and ask
the students what they think this model simulates. Add a small amount of water, about a teaspoon.
Have the student crunch and mix the bag some more. Ask the students what they think the small
amount of water in the model simulates.
Answer: This simulates chewing the food. The water represents saliva that is used to moisten the food
and begins the chemical digestion process.
3. Tell the students that you decided to have a banana with your graham cracker. Add a banana and
about ½ cup water to the bag. Have another student squish the banana, water and graham cracker in
the bag carefully. Ask them where water in the digestive system might come from.
Ask the students where they think the food would go next. There is no tube to simulate the esophagus,
so you will have to address this.
Answer: The food is swallowed and goes down through the esophagus and into the stomach. The water
can come from saliva or drinking water. The water also comes from the acid solution that is secreted in
the stomach. Food in the stomach is churned and mixed with acid and enzymes. The food continues to
break down.
4. Ask a third student to hold one of the nylon knee-high hose under the Ziploc bag and the teacher
should cut a small hole in the corner of the bag so that the slurry runs out into the nylon. Be sure to
have a tray to catch the liquid underneath the hose. The student should squeeze as much of the
contents out of the bag into the hose as they can. Ask the students where the food goes next in the
digestion process and what happens there.
Answer: The food moves to the small intestine. That is where the majority of nutrients are absorbed by
the body.
5. As the water and dissolved materials leak out of the nylon hose, have the students identify what this
material represents in this model and where it would actually go if this were the body. Do not squeeze
the liquid out of the nylon yet, that happens in the next step.
Answer: This liquid represents nutrients and water that are being absorbed by the body. They go into
the blood stream and are carried to the parts of the body that need them.
6. Ask a fourth student to hold a new nylon knee-high hose (use one that is a different color and cut a
small slit in the toe) under the “small intestine”. Ask the students where they think food goes when it
leaves it small intestine and what happens there. The teacher should cu the tip off of the hose that
represents the small intestine so that the remaining slurry runs into the second nylon. If the student is
willing, they could gently squeeze the contents in the second nylon hose to help some water to come
out of the hose.
Answer: The food goes into the large intestine where water is absorbed and feces are formed.
Note: This could be a good time to discuss what would happen if the water was not absorbed here in the
“large intestine” because it is very difficult to get enough water out of the hose to simulate the
consistency of normal feces!
Activity: Esophageal demonstration
Activity: finger painting or play dough model of systems-have students paint or mold one of the
digestive systems then label each part
Other suggested activities:
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Cow/pig stomach digestion
Rumination Game: http://www.ellenjmchenry.com/homeschool-freedownloads/lifesciencesgames/ruminationgame.php
Brochure Activity- Research one common problem of the digestive system, such as constipation,
gas, lactose intolerance, or ulcers create a brochure, similar to one found at a doctor's office,
that describes the problem, its causes, symptoms, and possible treatments
Evaluation/Summary
Level of content mastery will be determined by teacher made test or quiz. The evaluation should check
for understanding of the following:
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Examples of ruminant and non-ruminant (monogastric) animals
Physical traits that differ between ruminant and non-ruminant animals
Modified digestive systems such as the horse, rabbit, and chicken
Anatomy of the digestive tract and the function of each
The flow of digestion through the various animal digestive tracts
Mechanical/chemical breakdown and examples of each
Chemicals necessary for chemical breakdown (saliva, stomach, intestines)
The way in which nutrients get to the rest of the body after digestion
Issues of the digestive system (stomach upset, diarrhea, constipation)
References/Additional Materials/Extended Learning Opportunities/Enrichment
Cornell
“Digestive Systems” PowerPoint
Monogastric Handout
Ruminant Handout
Digestive Tracts
Motivation Materials
College and Career Readiness Standards:
Science
I. C1-3 Demonstrate skill in the safe use of a wide variety of apparatuses, equipment, techniques and
procedures
V. D1 Understand that scientists categorize things according to similarities and differences
VI. E 1 Know ways in which living things can be classified based on each organism’s internal and external
structure, development, and relatedness of DNA sequences
VI F2 Describe, compare and contrast structures and processes that allow gas exchange, nutrient uptake
and processing, wast and excretion, nervous and hormonal regulation, and reproduction in plants,
animals, fungi; give examples of each
VI. G3 Understand typical forms of organismal behavior