Sheep Heart Dissection

Author(s): Chris Cain and Soroya Wood

Lesson Overview

Grade level(s):

Grade 5

Subjects(s):

Biology/Life Science

Topic:

Heart, Circulatory System

Big ideas(s):

Understanding the role the heart plays in the circulatory system by working hands-on with a real heart

Looking at structures can help us understand function (how something works)

Vocabulary words:

Dissection, Heart, Aorta, Valve, Septum, Ventricle, Atrium

What you need:

Dissecting Scissors, Lab Coats, Lab Safety Glasses/goggles, Gloves, Dissecting trays- all of these can be obtained from SEP's Resource Center.

Sheep Hearts. 2 options are:
1) Biobag pack of 30 can be obtained from Carolina Biological, ~$90 for 30; http://www.carolina.com/home.do) Order from Carlolina at least two weeks in advance. Hearts can be stored at room temperature. They are in a non-toxic preservative and can be discarded after the lesson.

2) Purchase them in San Francisco from a wholesale butcher such as Golden Gate Meat Company (http://www.goldengatemeatcompany.com/ or 415-861-3800). With 3 weeks lead time, you can order non-edible versions that leave more structures in place. With less time, you can purchase the frozen ones. Allow to thaw for at least 1 day and rinse well with water.

Grouping:

Students were grouped in pairs, two students for every one sheep heart. This worked well - students could take turns, and the "squeamish" factor meant one partner did not have to be as hands on to see what was going on.

Setting:

Standard classroom

Time needed:

With 5th graders, this lesson took us 90 minutes on our first run through. It could probably be shortened to 75 minutes, but an extended period is best for this very hands-on activity.

Author Name(s): 
Chris Cain and Soroya Wood
Summary: 

Students observe and dissect a sheep heart. In doing so, they learn about how the heart works and what it really looks like.

While this lesson is adaptable for many grade levels, it is a great fit with California's FOSS 5th grade Living Systems kit and that kit's goal of learning the structures and functions of the circulatory system.

Prerequisites for students: 

A basic understanding of the circulatory system.

Learning goals/objectives for students: 

Identify the four chambers of the heart, the valves, and the blood vessels that flow in and out of the heart. Students will be able to see how the heart is similar and different from what is presented in textbooks, on charts and models, etc. They should be able to identify how form follows function by seeing the structure of the heart.

Content background for instructor: 

The human heart weighs less than a pound and is generally a little larger than the person's fist. The heart is a hard-working muscle that pumps blood to the lungs and throughout all the body. The heart is basically hollow with walls made of muscle; the septum divides the heart cavity into a right and left heart. Each side of the heart is divided into an upper chamber (atrium) and lower chamber (ventricle). The heart works as a double pump with the right heart receiving blood that has come from the body and is depleted of oxygen. This blood is pumped to the lungs where the blood gets rid of carbon dioxide and picks up oxygen. The left heart pumps oxygenated blood through the aorta and it then travesl throughout the body.

For more background info, one useful resoruce is the Texas Heart Institute website listed in the links at the end of this lesson plan.

Sheep heart structure is very similar to human hearts. The human heart is approximately 1.5-2 times bigger than a sheep heart.

Getting ready: 

Obtain sheep hearts and other materials listed under "what you need." Students should wear gloves, lab coats, and goggles at all times. Set-up/passing out materials for the lesson will likely take about 10 minutes. We did one test cut of a heart before the lesson, and determined two simple cuts was best. If you have not done a heart dissection before, we highly recommend you spend at least 10-15 minutes cutting open a heart for yourself, before starting the lesson with the class. There are 2 photos attached to this lesson. Photo 1 shows where the first cut is made in this heart dissection. Photo 2 shows the heart after it has been cut in half and a person is measuring the thickness of the heart wall.

Lesson Implementation / Outline

Introduction: 

The lesson was started with a 5-10 minute overview of the circulatory system. The mneumonic device "Right Back" was used to emphasize that the right side of the heart pumps blood back to the lungs, while the left side pumps it out to the body. The terms "Atrium" and "Ventricle" were reintroduced, with "A comes before V, so A is on top of V" used as a trick for remembering which was which. This was done in an interactive "Q+A" way.

Activity: 

Students spent ~10 minutes getting lab coats, gloves, and goggles on, and having a dissecting tray with heart placed in front of them. Students were told to spend 5 minutes just observing the heart. Which is the top and which is the bottom? Front/Back? Does their heart look like their neighbors?  The point was made that all the hearts look a little different, but they were all functioning hearts. Just like we are all unique, our insides are all a little bit different too.

This dissection was simplified to be very straightforward. It involves 2 cuts. Each cut was demonstrated in front of the class for the students, and then students were given 5-10 minutes to cut and investigate while teachers circled the room helping out.

Cut #1 - The bottom half of the heart is cut away. This exposes the two ventricles at the base of the heart, separated by a large thick wall (the septum). Students made this cut, then observed the chambers inside of the heart. After about 5 minutes, we brought the class back and asked students if they had any questions or comments about what they saw. We asked which might be the right side, and which was left. The point was made that the left side of the heart needs to have a much thicker wall around it, so that it can contract and squeeze blood out to the entire body. Students were given rulers and told to measure the size of the wall of the right vs. left side of the heart. A few students were called on to report their measurements.

Cut #2 - The heart is cut up through the center of the septum, the wall dividing the ventricles. This is a more difficult cut to do, as the hearts are large and the scissors are small. We cut the heart clean in half, into two separate pieces, for easiest observation.

Students were told to look around, feel and touch the inside of the heart. Many comments were that "the heart is smooth", "there are strings holding the heart together" (Commonly called Heart Strings, that is exactly what they are, they keep the heart together and beating properly). Students could put their finger through the aorta at the top of the heart and feel inside, connecting the blood vessel to the chambers of the heart. In some cases it was possible to see small flaps of skin, the valves, which separate the chambers of the heart.

Wrap-up / Closure: 

This is a very hands-on, experiential lesson. Students asked questions and were monitored throughout the lesson. At the end, revisit the idea of how, often times, looking closely at structure (in this case, a heart) can help us understand how it functions.

A discussion of what was surprising and/or most interesting would provide insights into what students learned and/or valued in the lesson. Students could also do this as a written reflection.

Students could be asked to draw, diagram, and take notes throughout the dissection or to do this at the end (it can be hard to draw/write whie doing dissections).

The American Heart Association has worksheets with a heart diagram.  See the link at the end of this lesson and click on "Follow the Blood" and "Label the Heart's Parts."

Extensions and Reflections

Extensions and connections: 

One extension of this lesson is to borrow healthy and diseased human hearts from SEP's Resource Center.

Reflections: 

This lesson went very well, and it was our first time ever dissecting a heart. Students were extremely excited about the opportunity to see what a real heart looks like. Given the time we spent explaining and reflecting, our lesson went a full 90 minutes - more than we had anticipated. Really, the experience of cutting open the heart and poking around brought some reality and excitement to the unit of the circulatory system and it does not necessarily require extensive reflection. The hearts were easily disposed of in the garbage, and non-toxic with very little smell. We would highly recommend this lesson to any classroom as a real "treat" for the students.

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First Cut Heart Dissection.jpg78.24 KB
Heart Dissection Photo.jpg92.07 KB

California Standards - Grade 3

Life Sciences: 
3. Adaptations in physical structure or behavior may improve an organism's chance for survival. As a basis for understanding this concept:
a. Students know plants and animals have structures that serve different functions in growth, survival, and reproduction.

California Standards - Grade 5

Life Sciences: 
2. Plants and animals have structures for respiration, digestion, waste disposal, and transport of materials. As a basis for understanding this concept:
a. Students know many multicellular organisms have specialized structures to support the transport of materials.
b. Students know how blood circulates through the heart chambers, lungs, and body and how carbon dioxide (CO2) and oxygen (O2) are exchanged in the lungs and tissues.

California Standards - Grade 7

Structure and Function in Living Systems: 
5. The anatomy and physiology of plants and animals illustrate the complementary nature of structure and function. As a basis for understanding this concept:
a. Students know plants and animals have levels of organization for structure and function, including cells, tissues, organs, organ systems, and the whole organism.
b. Students know organ systems function because of the contributions of individual organs, tissues, and cells. The failure of any part can affect the entire system.

California Standards - Grades 9-12 Biology

Physiology: 
a. Students know how the complementary activity of major body systems provides cells with oxygen and nutrients and removes toxic waste products such as carbon dioxide.