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Examining the Heart

Examining the Heart

Interior of a sheep's heart.
© Baylor College of Medicine\JP Denk.

  • Grades:
  • Length: 60 Minutes


Mammals and birds, including humans, sheep and chickens, have four-chambered hearts. This design completely segregates oxygen-rich from oxygen-poor blood. In this lesson, students examine sheep or chicken hearts to learn about heart structure and the flow of blood through the heart.

This activity is from The Science of the Heart and Circulation Teacher's Guide, and was designed for students in grades 6–8. Lessons from the guide may be used with other grade levels as deemed appropriate.

Teacher Background

The heart is made mostly of a special kind of muscle, known as cardiac muscle, which is very resistant to fatigue. Cardiac muscle cells are able to contract on their own, without receiving stimulation from the nervous system. Due to this important characteristic, the heart does not require a signal from the brain or spinal cord every time it needs to contract. A small bundle of nervous tissue, called the sinoatrial node (SA node), in the wall of the right atrium initiates each contraction and serves as a “pacemaker,” setting the rate and timing of heartbeats. The signal from the sinoatrial node spreads to another small bundle of nervous tissue, the atrioventricular node (AV node), located in the heart wall between the two chambers on the right side of the heart. Together, the SA and AV nodes regulate contractions of the ventricles and atria, and allow the heart to work as an efficient double pump. Additional signals about pace can come from the brain (nervous system) and hormones (endocrine system). Fever also raises heart rate.

The heart is a double pump with four chambers. The two upper chambers, the atria, receive blood returning from the body (right atrium) and the lungs (left atrium), and pass it into the lower chambers, the ventricles, so that they can pump it to all other areas of the body. As students examine and dissect a heart, be sure they note the thick, muscular, elastic walls that allow the ventricles to pump blood effectively throughout the body. The walls of the atria are not as thick as those of the ventricles. Students also should note that there are several one-way valves in the heart that prevent blood from moving backward from the atria into the veins, from the ventricles back into the atria, and from the arteries back into the ventricles.

Objectives and Standards

Life Science

  • Living systems at all levels of organization demonstrate the complementary nature of structure and function. Important levels of organization for structure and function include cells, organs, tissues, organ systems, whole organisms and ecosystems.

  • Specialized cells perform specialized functions in multicellular organisms. Groups of specialized cells cooperate to form a tissue, such as a muscle.

  • The human organism has systems for digestion, respiration, reproduction, circulation, excretion, movement, control and coordination, and for protection from disease.

Science, Health and Math Skills

  • Observing

  • Comparing and contrasting

  • Relating knowledge

Materials and Setup

Teacher Materials (see Setup, below)

  • Masking tape and long pins

  • PowerPoint® slides or transparencies of all student sheets

Materials per Group of Students

  • 13 long pins with masking tape flags

  • 2 pipe cleaners

  • Sheep heart (preserved) or chicken heart (fresh)

  • Lab notebook or sheets of paper

  • Paper plate

  • Pair of dissecting scissors, plastic knife or scalpel

  • Dissection kit

  • Dissection tray

Materials per Student

  • Highlighting marker

  • Magnifier

  • Pair of disposable gloves

  • Pair of safety goggles

  • Copy of student sheets (see Lesson pdf)

  • Copy of "The Heart: External," and "Inside the Heart," (see "Lesson Media" tab, above).


  1. Purchase chicken hearts from a grocery store or order sheep hearts from a biological supply company. Sheep hearts are preserved and can be used for several weeks. Keep the sheep hearts in tightly sealed plastic bags.

  2. Place all necessary dissecting materials on paper plates or trays, with one set of materials for each student group. Make pins with masking tape flags for each group, or have students make their own. Have students perform the dissections in groups of four.

  3. Make copies of all student sheets listed under "Materials per Student."

Note: This activity may be conducted as a class demonstration. Or visit the Virtual Heart Web site ( to provide a three-dimensional class demonstration of the heart’s structures.

Procedure and Extensions

Part One: Exterior of the Heart
  1. Discuss students’ previous explorations of the exterior and interior of the heart. Ask students to share any questions they still have about the heart’s structure or function. Record their questions to refer to at the end of this activity.

  2. Tell students that they will be examining chicken or sheep hearts similar to the ones they viewed in the videos previously.

    Safety Note: Be sure all students wear gloves and safety goggles, even if they only will touch the heart. Inform students that there will be no blood involved in the dissection (it is clotted). Monitor students, as some people may begin to feel a little uncomfortable during the procedure.

  3. Distribute copies of the “Heart Dissection” page and have students read it within their groups.

  4. Have each Materials Manager pick up a tray of materials for his or her group.

  5. Have students examine the heart specimens. Ask, How does the heart feel when you touch it? [smooth, tough, rubbery] If using sheep hearts, explain to students that the heart’s texture has been altered by the preservation chemicals. Have students locate, and then gently press on, the upper and lower chambers of their heart specimens. Ask, Does one part feel thicker or more muscular than another? [There is more muscle around the lower chambers.]

  6. Because most diagrams show the anterior (front) view, the right side of the heart appears on the left side of the diagram. To demonstrate this to your class, ask each student to face another student and raise his or her right hand. Explain that they are looking at an anterior (front) view of their partner student’s body. Therefore, each student’s right hand will appear on the left for his/her partner. The same will be true when they study a ventral view of the heart.

  7. Have students continue to observe the heart by following the dissection instruction sheet.

  8. After students have completed “Part One: Exterior of the Heart,” review what they have learned so far. You may wish to display a copy of the worksheet while students check the location of the pins on their specimen hearts. Ask each group to check another group’s work and discuss any differences. Or, have students create their own labeled drawings.

  9. Have students remove all pins from their specimens before proceeding to Part Two.

Part Two: Interior of the Heart
  1. Before they begin, instruct students on the proper way to handle sharp instruments. You may demonstrate how to make the first cut into the heart, or simply complete this step for students.

    First, insert the point of a pair of dissection scissors, plastic knife or scalpel into the superior vena cava (large vein that enters the right atrium—sometimes present only as a large hole). Cut down the superior vena cava into the wall of the right atrium and continue down to the apex of the heart. Students should be able to see the right atrium and ventricle.

  2. Students will use Part Two of the student sheet to complete the heart dissection.

    Note: You may want to assist students when they open the left atrium and ventricle. Insert scissors or knife into one of the pulmonary veins (may appear as a large hole) on the left side of the heart, and cut through the wall of the left atrium. Once again, continue forward toward the apex (or tip) of the heart.

  3. Distribute copies of the “Blood Pathways” sheet to each student. Have students read the descriptions of how blood flows through the heart.

  4. If using sheep hearts, have students discuss and demonstrate the flow of blood through the heart specimen, beginning with the point of entry at the superior vena cava. Have students push pipe cleaners through the large vessels to discover where they lead.

  5. Once students understand the flow of blood via heart-lung-heart-body circulation, explain that the right and left atria contract at the same time, followed by contractions of right and left ventricles. In a properly functioning heart, the synchronized work of the four chambers will cause the atria to expand and fill with blood as the ventricles are contracting.

  6. When finished, students should clean and return all dissection equipment. Have students clean their desktops and wash their hands thoroughly with soap and water. Dispose of hearts properly (see "Safety").

  7. Revisit and discuss students’ questions about the heart. Have students add new information and observations to their concept maps.

Handouts and Downloads

Download color images from The Science of the Heart and Circulation Teacher's Guide.

Inside the Heart

Student sheet with a labeled illustration and photograph of the interior of the heart.

The Heart: External

Student page with illustrations and photos of the heart (external views).

Related Content

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    Heart and Circulation Teacher Guide

    Students investigate the heart's structure and function, blood pathways, how volumes of blood are moved through the body, and the effects of microgravity on the heart. (9 activities)


National Space Biomedical Research Institute

National Space Biomedical Research Institute

This work was supported by National Space Biomedical Research Institute through NASA cooperative agreement NCC 9-58.