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The Human Heart

The Human Heart

Introduction: (Initial Observation)

Did you give your friends valentines and little heart-shaped candies on Valentine’s Day? Do you ever cross your heart when making a promise that you really, really mean? Or turn on the radio to hear a guy singing about his broken heart? We see and hear about hearts everywhere. A long time ago, people even thought that their emotions came from their hearts, because the heart beats faster when a person is scared or excited. Now we know that emotions come from the brain, and that the brain tells the heart what to do. So what’s the heart up to, then? How does it keep busy? What does it look like? Well, it isn’t like the heart on valentines, that’s for sure. It’s much more interesting than that. In this project you will investigate on heart! what it does and how it works.


This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Adult help and supervision is required.

Information Gathering:

Find out about human heart and how it works. Read books, magazines or ask professionals who might know about the hear. Keep track of where you got your information from.

Memorize and explain different sections of heart and their function. Draw an enlarged illustration of the heart and label all sections.

The heart is a muscular organ located just to the left of the breast bone
(sternum). It is about the size of your fist, and this amazing muscle pumps
4300 gallons of blood a day. The heart has four chambers:
 Atria. The top two chambers that receive blood from the body or lungs.
Ventricles. These are the bottom two chambers of the heart. The right ventricle pumps blood to the lungs to pick up oxygen, The left ventricle pumps blood to the rest of the body and is the strongest chamber.
Valves. There are four valves in the heart that help to direct blood flow. As they open and close, the valves produce sounds that can be heard with a stethoscope. The heart sounds can often tell your doctor about your heart’s function. 

Function of the Heart Every cell in your body needs oxygen in order to live and function. The role
of the heart is to deliver the oxygen-rich blood to every cell in the body.
The arteries are the passageways through which the blood is delivered.
The largest artery is the aorta, which branches off the heart and then
divides into many smaller arteries. The veins carry the deoxygenated blood
back to the lungs to pick up more oxygen, and then back to the heart once
again. Blood flows continuously through the circulatory system, and the
heart muscle is the pump which makes it all possible!

Amazing Heart Facts

  • Your heart is about the same size as your fist.
  • An average adult body contains about five quarts of blood.
  • All the blood vessels in the body joined end to end would stretch 62,000 miles or two and a half times around the earth.
  • The heart circulates the body’s blood supply about 1,000 times each day.
  • The heart pumps the equivalent of 5,000 to 6,000 quarts of blood each day.

Activity 1:

  • View a movie to find out background on the heart and circulatory system. You will watch a 3 minute movie clip and answer a 3 minute quiz. Write answers to quiz in your Science notebook.
  • READ all directions before clicking on website:

a. Click on Play Movie. This movie is approximately 3 minutes long. When movie is finished, do the quiz.
b. Click on Play the Quiz This will take approximately 3 minutes.

Now Click here to see movie.

Activity 2:

  • In this activity , you will be viewing a virtual tour of the heart. There are 3 parts to the tour.
    • READ all directions before clicking on website:
    • Once you open the linked web page, click on English, human heart.
      Then click on Heart parts and follow the directions. When you are done click on the Heart word on the bottom of the page.
    • Then click on the animated heart and click on the parts to find out the name of each part. When you are done click on the Heart word at the bottom.
    • Last click on the Narrated tour and listen to the tour. When the first part finishes, click on the blue arrow to see the second half of the tour. Then return to this web page by clicking on the BACK green arrow button at top of the page.
      Click on: Medtropolis

Activity 3:

  • View this lesson on the parts of the heart and answer the questions on-line.
  • When finished press the BACK green arrow key to return to this web page.
    Click on: Kidport

Activity 4:

  • READ all directions before clicking on website:
  • View the heart on this web page, and click on each label and read the descriptions of each part of the heart. Press BACK button after each word to return to the diagram.
  • You will use this information to fill in Activity 5.
    When you are done press the BACK arrow key until you are back to this web page.
    To view a large diagram of the heart click here!

Activity 5:

  • You will be viewing a template of the heart. Write the numbers 1-9 on your science notebook and write the corresponding answers. Turn in your notebook.

Look at this sheet and write the numbers 1-9 on your notebook.

Activity 6:

  • If you are familiar with using clay or other modeling material, you may want to make a model of heart from clay. To do this, first form a clay to the shape of heart as it is seen from outside. Then before it gets fully dry, use a pulled string to cut a layer from the heart about 1/2″ thick. This will expose the area that atriums and ventricles must be carved.
  • Use a small spoon or wooden modeling tools to cut the atriums and ventricles from each half.
  • Make rods or tubes of clay and connect them as veins and arteries.
  • Let it dry and then use water based paints to paint each half. Use the following image while carving the atriums and ventricles.


artery: one of the tubular vessels that carry blood away from the heart

aorta: the main artery that carries blood away from the heart

atrium: one of the hollow cavities of the heart

blood: the liquid that circulates in the heart, arteries, and veins

pulmonary circulation: circulation of blood between the heart and lungs

red blood cell: saucer-shaped cell in blood plasma that carries oxygen

Valve: A structure that folds or closes to prevent the return flow of the blood passing through

vein: one of the tubular branching vessels that carry blood from the capillaries toward the heart

ventricle: a chamber of the heart that receives blood from the atrium of the same side and pumps it into the arteries

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

  1. What does the heart sound represent? How do the valves work?
  2. What happens during the pumping action of the heart?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

For this project you will not need to identify any variables because you are not studying the effect of something in something else. For example if you wanted to study the effect of air pressure on the rate of heart beat, then you had to identify variables. In that case for example you would say that air pressure is an independent variable and the rate of heart beat is a dependent variable. By using these terms you would make it clear that the rate of heart beat depends on or can be affected by air pressure.


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

With the same reason explained above, you do not need to propose a hypothesis. However a sample hypothesis for the effect of air pressure on the rate of heart beat is like this:

I hypothesize that lower air pressure will increase the rate of heart beat.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1:

What does the heart sound represent? How do the valves work?

For this experiment we will make models of valves to see how do they work and why do they make sound.


  • Scissors
  • Glue
  • Compass (for drawing circle)
  • Construction Paper
  • Large Thread Spool
  • Timer (Optional, to simulate heart bit sound)
  • Pencil
  • Transparent Tape


  1. Cut and glue a circle of construction paper to cover each end of the thread spool. Allow the glue to dry for several hours.
  2. Use a pencil to punch a hole in each paper circle to line up with the hole in the spool.
  3. Cut a smaller paper circle about 1 inch (2.5 cm) in diameter.
  4. Center this small paper circle over the paper circle on one end of the spool, and secure it on one side with a piece of tape about 1/4 inch (0.6 cm) wide. This makes a flap over the hole.
  5. With your mouth, blow through the hole in the uncovered end of the spool so that the paper flap on the other end opens out.
  6. Suck air back through the hole with enough force to cause the paper flap to close against the end of the spool.
  7. Repeat the blowing and sucking of air through the hole in the spool.
  8. Listen to the sound made as the paper flap opens and closes.


A swishing sound is heard when the flap opens out, and a thumping sound each time the flap closes.


In all mammals, the heart is a double pump. Each side of the heart has an upper and lower chamber. The top chambers are called atriums and the lower chambers are called ventricles. A one-way flap called a valve (structure that controls blood flow in one direction) connects the upper and lower chambers.

When the heart muscle relaxes, blood flows through the open valves from the atriums into the ventricles. When the heart contracts, the flap is closed with a thump. The valve prevents the blood from moving back into the atrium, and it is forced out of the heart through another opening. The opening and closing of the paper flap on the thread spool produces a sound like that made by heart valves.

The sound from the valves can be heard through the tissues (groups of similar cells that perform special functions) of the body and is often described as a lub-dub sound.


Would a hole in the flap affect the sound? Repeat the experiment, making a small hole in the paper flap. Repeat several times, making increasingly larger holes in the flap.


How can blood flow in only one direction in veins? Veins (blood vessels that carry blood to the heart) have valves. Build a model using a box and two flaps of stiff paper to demonstrate the movement of blood through the one-way valves in blood vessels. Use a marble to represent blood.

Tape one flap to one of the long sides of the box so that it moves when the marble hits it. This is the movable flap. Tape the other flap to the opposite side of the box. This is the stationary flap. Make sure the stationary flap is wide enough so that the movable flap overlaps it by about 1/2 inch (1.25 cm). Put the marble in the box and tilt the box forward so that the marble hit the movable flap and opens it. Tilt the container backward, and the marble hits against the flap, closing it

Use your model, along with diagrams of a vein, as part of a project display. Find out how blood flows in arteries (blood vessels that carry blood away from the heart).

Experiment 2:

In this experiment we will see what happens during the pumping action of the heart?


  • wide mouth jar
  • 2 small balloons, one large balloon
  • skewer or toothpick
  • two flexible straws
  • scissors
  • tub or pail to collect water spills
  • sponge


1. To make a one directional valve, cut about 4 centimeters (1.5 inches) from the small balloon and then insert about 1 centimeter of one straw in it. Use cotton string or tape to secure it in place.

2. To make the second one directional valve, cut a strip of rubber balloon slightly wider than the diameter of the straw. This will be a rectangular piece about 1/2″ wide and 2″ long. Place it on the tip of the second straw and secure it with a tape.

At this time you should have two straws with one valve on each straw. Note that the valve made with the yellow balloon allows the air and liquids to exit the straw, but does not allow the air or liquids to enter the straw. You can test it by trying to blow in or suck out air from the other end of the straw.

On the other hand, the valve made with the pink balloon allows the air and liquids to exit the straw, but does not allow the air or liquids to enter the straw. You can test it by trying to blow in or suck out air from the other end of the straw.

3. Cut a large piece from your large balloon. With the skewer or toothpick, poke two small holes into the balloon, about 2 cm apart. Carefully insert straws in the holes in a way that the valves stay on two opposite sides of the balloon.

The straws should fit snugly. If there are gaps between the straws and the balloon, start over with a new balloon.

Stretch the balloon.

4. Fill the jar half full with water. Stretch the balloon with straws over the mouth of the jar so it fits tightly. Hold the balloon stretched and ask your assistant to wrap and tie a cotton string around the neck of the jar. This should hold the balloon sealed and air tight.

At this time the two straws (one with a pink valve) should be in the water and close to the bottom of the jar.

Bend down the straw with the yellow balloon valve. Place the jar in a tub or pail.

5. Push and release the balloon stretched over the jar several times.
Can you get water to move through the straws? In what direction does the water move?

This experiment will show that the expansion and contraction of the heart will cause a one directional flow of blood through one directional valves in heart.

Aortic valve and pulmonic valve allow the blood exit the heart, but do not allow the return of the blood to the heart. These two valves work like the long yellow valve in your model.

Mitral Valve and tricuspid valve allow the blood enter the heart, but do not allow any blood to exit.


1. Study illustrations of the heart. What are the similarities between the heart and the pump you assembled?

2. Remove the balloon flap (valve) from the apparatus. What happened?

3. Does the valve affect how well the water flows?

4. Can you think of other examples of valves and pumps?

Notes to parents: Lub Dub

The heart contains valves which direct the flow of blood in one direction. Blood is forced through the flexible membranes which form the valves. Once the blood passes through the membranes, the valves collapse into a barrier, preventing the blood from flowing backwards.

Students can find examples of pumps and valves in facets, aerosol sprays, automobile fuel pumps, and many household items in daily use. Some beverage containers use a valve that resembles the valves in the heart.

Point out to the students that the heart is a muscle and not a mechanical pump. It can also be pointed out that comparisons of this kind are known as reasoning by analogy and are an important part of scientific reasoning.

A Plastic Heart (Just another design)

This is a different method of making a plastic heart model. In this model we use a plastic cup to hold the blood (or any other liquid). Valves are very similar to real heart valves. We cut about one inch from the neck of a small balloon and used it as a valve. The yellow balloon is the input valve and the green balloon is the output valve.

To make this model first we made two holes on the sides of the plastic cup with the diameter of 3/8″. We selected this diameter to match the clear plastic tube that we already had. Two clear plastic tubes that are about two inches long each are inserted into the holes in a way that about 1/2″ (or less) stays inside the tube. Use hot melt glue around each hole to seal the gap between the hole and the plastic tubes.

Then we inserted two balloons, one on each side. For the green balloon we also inserted the balloon inside the tube to act like an exit valve. To make sure that the green balloon does not pop back inside the cup, we also inserted a small piece of straw inside the green balloon. Finally the cup is covered with a piece of larger balloon which is secured using rubber bands.

Finally we connected a flexible rubber tube to the input pipe and inserted the other end of rubber tube into a cup of water. Pushing the balloon up and down pulled the water into the cup and then exited from the other side.

Materials and Equipment:

List of material can be extracted from the experiment section.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.


No calculation is required for this project.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.


List of References

Listen to the Heartbeats

Hear some different heart rates and try to guess which is which. Site done by the Franklin Institute’s online heart exploration.

How Your Heart Works

Along with a basic diagram of the heart, this page by Dr. Carl Bianco, M.D. gives an overview of how the heart functions, especially concerning the heart’s chambers and valves.

3D Tour

This 3d tour inside the heart helps the viewer to grasp the concept of the heart’s inner workings, as well as providing an excellent internal and external view of the heart.

Hart Monitor


The cause of high blood pressure

Blood Pressure

Heart diseases


A. The thread spool experiment is only a demonstration or display experiment. It does not have any measurements and it does not require a graph.

If you need a graph, you may compare the heart bit rate of people in different ages. For example you may try the ages of 1 to 10, 11 to 20, 31 to 40, and 41 to 50.

Then you can make a bar graph with one vertical bar for each age range. The height of each bar will represent the average rate of heat bit in that age range.

The table below shows estimated heart rates for different ages.

Age Target HR Zone
50–85 %
Average Maximum
Heart Rate
100 %
20 years 100–170 beats per minute 200 beats per minute
25 years 98–166 beats per minute 195 beats per minute
30 years 95–162 beats per minute 190 beats per minute
35 years 93–157 beats per minute 185 beats per minute
40 years 90–153 beats per minute 180 beats per minute
45 years 88–149 beats per minute 175 beats per minute
50 years 85–145 beats per minute 170 beats per minute
55 years 83–140 beats per minute 165 beats per minute
60 years 80–136 beats per minute 160 beats per minute
65 years 78–132 beats per minute 155 beats per minute
70 years 75–128 beats per minute 150 beats per minute

Your maximum heart rate is about 220 minus your age. The figures above are averages, so use them as general guidelines. This is a sample line graph. It also shows that people who exercise have a higher rate of heart bit.

The Heart and the Circulatory System

Anterior: adjective referring to front end of an animal or organism.

Aorta: the main systemic artery of the body, emerging directly from the left ventricle.

Arteriole: a small arterial branch that delivers blood directly to a capillary bed.

Artery: a muscular blood vessel that carries blood away from the heart.

Arthropod: Phylum which is bilaterally symmetric segmented animal with tough, chitinous exoskeleton. Phylum contains crustaceans, insects, spiders, centipedes and millipedes.

Atrium: one of the chambers of the heart that receives blood directly from a vein.

Circulatory system: the system of the body responsible for internal transport. Composed of the heart, blood vessels, lymphatic vessels, lymph, and the blood.

Closed circulatory system: a type of circulatory system where the blood is contained within a system of vessels and the heart.

Coronary artery: one of the arteries that supply blood to the heart.

Coronary vein: one of the veins that receive blood from the heart muscle and empty directly into the right atrium.

Deoxygenated blood: blood that is low in oxygen concentration.

Dorsal: adjective referring to the top or upper surface of an organism.

Heart: the muscular organ composed of cardiac muscle that is responsible for pumping blood throughout the body.

Heart attack: a condition occurring when a section of the heart is deprived of oxygenated blood and dies.

Interstitial fluid: the fluid filling the microscopic spaces between cells of the body.

Mollusca: phylum of bilaterally symmetrical invertebrates. Primarily marine invertebrates, but also includes land snails and slugs.

Open circulatory system: a type of circulatory system where the blood is not contained within a system of vessels and the heart. Blood empties from vessels into sinuses and then returns through other vessels to a “heart.”.

Peristalsis: wave-like muscular contractions in the walls of tubular organs, e.g. the alimentary canal. Peristalsis serves to push material contained within the organ along its length.

Posterior: adjective referring to the hind end of an animal.

Pulmonary artery: one of the arteries carrying deoxygenated blood from the heart to the lungs.

Septum: the wall dividing the two ventricles.

Sinus: a cavity into which blood flows and baths the internal organs in organisms with an open circulatory system.

Spiracle: opening which leads to a trachea in an insect, arachnid, isopod, centipede or millipede.

Vein: one of the blood vessels that carries blood to the heart.

Ventral: adjective referring to the lower surface of an animal or organism.

Ventricle: one of the muscular chambers of the heart that is responsible for pumping blood from the heart into the arteries.

Venule : a small venous branch that carries blood from a capillary bed to a vein.