STEM Club: The Circulatory System - Eva Varga

December 31, 2014

The Circulatory System consists of the heart, blood vessels, and the approximately 5 liters of blood that the blood vessels transport. Responsible for transporting oxygen, nutrients, hormones, and cellular waste products throughout the body, the cardiovascular system is powered by the body’s hardest-working organ — the heart, which is only about the size of a closed fist. Even at rest, the average heart easily pumps over 5 liters of blood throughout the body every minute.



The Heart

The heart, blood, and blood vessels are responsible for distributing the life-giving substances – oxygen and nutrients – throughout the body. Circulation begins with the heart. The heart is a large muscle that squeezes itself about once every second, sending blood flowing throughout the body’s network of blood vessels.

diagramheartThe hollow, muscular heart organ is divided into two sides or pumps. The left side sends blood to the aorta (the large blood vessel that leaves the heart) and through arteries, smaller arterioles, and capillaries (the smallest blood vessels in the body) to all the cells in the body. This blood transports oxygen to the cells and picks up carbon dioxide in return.

On the return trip, the blood travels in smaller veins (blood vessels that carry blood back to the heart) that connect to larger veins and eventually to the vena cava, the large vein that leads to the right side of the heart. The right side of the heart pumps the blood up to the lungs (via the pulmonary vein), where it takes in a new supply of oxygen and releases carbon dioxide. The blood then makes a quick trip back to the left side of the heart and the cycle begins again.

You hear two sounds during every heartbeat that goes something like this:     lub-DUB        lub-DUB        lub-DUB

Lub is the sound of the tricuspid and mitral heart valves shutting (on the top chambers). Then a pause as the top chambers relax. Dub is the sound of the semilunar heart valves closing. These valves shut off the big vessels leaving the heart. Then a longer pause.

The left side of the heart muscle is a bigger and stronger pump because it must push blood through the entire body. It takes about 23 seconds for the heart to circulate blood through the body.

In STEM Club, I first had the kids sketch a diagram of a heart in their notebooks and trace the route of blood flow through each chamber. When this was complete, we moved to the kitchen.

I had purchased a cow heart from a local butcher and intended to observe each of the heart chambers with my students. My goal was to identify the aorta, vena cava, left and right atriums, and left and right ventricles and thereby visualize the flow of blood through each.

We were able to do this to some extent, but weren’t completely successful because it was not whole. It had been cut in several places and it was difficult to discern one chamber from another as a result.

How Does Exercise Affect Your Pulse? – Group Inquiry Lab

When you feel your pulse, you are feeling blood as it is forced through an artery by the beating of your heart. Arteries are blood vessels that carry blood away from the heart. This pulse is the rate at which your heart beats.

Since the physical condition of an individual affects his heartbeat, pulse tests can be used to measure physical fitness.


  • Stopwatch
  • Data chart or notebook with the following columns:  Student Name / Inactive Pulse / Active Pulse / Recovery Pulse


  1. Guess how many times your heart beats in one minute ( _____ bpm) and record this in your notebook.
  2. Take your pulse and record it in the inactive column as _____ bpm.
  3. Record another’s pulse. If you are doing this in a co-op or small group setting, gather the results from everyone for a larger data set.
  4. Run in place or do jumping jacks for two – three minutes.
  5. Take your pulse and record it in the active column as _____ bpm.
  6. Rest for 5 minutes.
  7. Take your pulse and record it in the recovery column as _____ bpm.


  1. Have your pulses returned to normal?
  2. Compare your recovery rate to that of your peers.

Observing Blood

The average person’s body contains about 5 liters of blood. Blood is a tissue containing plasma, red and white blood cells, and cells called platelets. Fifty-five percent of blood is plasma which is ninety percent water, nutrients, oxygen and minerals. Forty-four percent of blood is made up of red blood cells. White blood cells and platelets make up about one percent.

  • Red Blood Cells are the disc-shaped cells in the plasma that carry oxygen. They are concave on both sides and do not have a nucleus. There are about 5 million in one cubic millimeter of blood. They get their color from an iron-containing protein called hemoglobin, which carries oxygen to the tissues. Red blood cells are made in the marrow of certain bones.
  • White Blood Cells fight infection. They are produced in bone marrow, lymph nodes, and in the spleen. They have a nucleus. There are about 7 thousand white blood cells per cubic millimeter of blood. There are about 7oo red blood cells for every one white blood cell. They fight infection by surrounding and engulfing the microbes that cause infection. Pus is composed largely of dead white blood cells.
  • Platelets stick to the walls of injured blood vessels and start the process of blood clotting.  This helps prevents blood from escaping. They release a chemical substance whenever there is an injury. This substance (along with other chemicals in the blood) form a mass of fibers that form the clot. Made in the marrow of bone, there are approximately 300,000 platelets per cubic millimeter of blood.


  • Prepared slides
  • Microscope with a minimum of 100x
  • Alternatively, you may use images found online


  1. Observe the prepared slides under a microscope and make a drawing of each type of blood cell.
  2. Create a data table in your notebook with the following columns:  Blood Cell Type / Description / Number of Cells in Field of View
  3. Record your observations.
  4. Include a sketch of each blood cell type.


  1. Which type of blood cell represents the largest number? [red cells]
  2. Describe the red blood cells. [disk-shaped, pink]
  3. What is the shape and color of the white blood cells? [shape of cell depends upon the shape of nucleus, which stains blue]
  4. Describe the different shapes of the stand nuclei in the white blood cells. [round, kidney-shaped, horseshoe-shaped, etc.]
  5. What are the solid parts of human blood? [red cells, white cells, platelets]
  6. Why are the centers of human red blood cells light in color? [there are no nuclei]
  7. How do red and white blood cells differ? [white blood cells are larger, have nuclei, are irregular shape, and are fewer in number than red blood cells]
  8. What do platelets do? [help clot the blood]

Bring it Home

  • Sketch the heart muscle in your notebook and label the major parts.
  • Design a test to show how your pulse rate varies with different exercise.
  • Write a story from the perspective of a blood cell as it journeys throughout the body.
  • Research the different blood types: A, B, AB, and O. Write a report detailing what you learned and include the following terms: antigens, antibody, and transfusion.
  • Donate blood at your local American Red Cross
  • Observe the veins, arteries, and capillaries on the underside of your tongue and below your eye. [thick blue lines = veins, thick pink lines = arteries, and thin lines = capillaries]
  • Design an test to determine whether a person’s body temperature remains constant all day.
  • Enjoy these Brain Pop videos:
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