Life Cycle - Human Biology (1B)

  • Experimenting with blood circulation.
  • Tracing the pattern of blood flow.
  • blood
  • circulation

Students watch blood move.



The circulatory system is responsible for the transport of body fluids such as blood and lymph and for the temperature regulation.  The heart pumps blood through a network of arteries and veins spread throughout the body.   For your own knowledge, the lymphatic circulatory system is structurally and functionally related to the blood circulatory system.  Lymph vessels are widely distributed throughout the body, but they are concerned with the transport of lymph which is concerned with immune defenses. 

Blood is a mixture of solid material and liquid.  The liquid portion, or plasma, provides a medium in which the solid portion can be transported.  Within the plasma are many substances, including water, inorganic salts, proteins, nitrogen bearing substances (urea), fats, cholesterol, sugars, hormones, and dissolved gases. (Note: do not confuse plasma, a state of matter with this meaning.)  The cellular solid portion includes red blood cells and variety of white blood cells and platelets.

This lab emphasizes how blood  moves in our body. Students will learn about the heart rate and how body position affects the heart rate.

The heart acts like a mechanical device whose function is to pump blood through the body to replenish oxygen lacking blood cells with oxygen. The importance of constant circulation of blood throughout the body cannot be overemphasized.  Without blood, life would not exist.  If blood does not reach the brain for just five seconds an individual loses consciousness; after 15-20 seconds the body begins to convulse (shake uncontrollably); and if nine minutes pass, irreparable damage to the brain results.  

The strong contraction of the heart muscle forces blood into the arteries in two ways:  the first expands the muscular walls of the arteries and the second pushes the blood through the arteries to regions of the body away from the heart.  This rhythm makes the arteries expand and produce a pulse.  In the wrist, the pulse is detected by a throbbing sensation near the surface.  The heart is composed of four chambers, two upper chambers, the right and left atria, and two lower ones, the right and left ventricles.

  1. Exploring the human body is very complicated.   This activity helps young children understand how the heart helps pump blood throughout the body  (circulation).  Read A Broken Heart to students.  Since the subject is a young girl with a bad heart it will draw their interest.  Make sure you point how the flow of the blood goes through the heart.  The movie at the end will help you see the movement.
  2. Use the circulatory worksheet  to show students the pattern of the circulatory system and where the heart can be found.  Make sure they note that it is a closed network.  We bleed when the closed network is cut. 
  3. Use the heart worksheet (pdf) to help the students see how the movement of the blood goes through the heart.  You can use the worksheet as a puzzle so the students can put the heart back together.  Blood that has been used from other parts of the body first goes through the right atrium, then the right ventricle, then pumped into the lungs.  There is a valve between them that controls the flow.   The lungs give the blood oxygen.  The blood that comes from the lungs first goes into the left atrium, then left ventricle and then is directed to other parts of the body so they can use the oxygen. The sound of the heart is the valves opening and closing.
  4. The second part of the lab has students mixing some "blood" by filling half a glass of water with a few drops of red food coloring.  Ask students how this blood moves through the body.  Many students may not be aware that blood moves through a network of tubes (arteries and veins).  Note that a child thinks that blood is just moving around in their bodies.  It is conceptually difficult to understand veins, arteries and capillaries in our bodies.  Capillaries are a net work of "roads" that allow communication between arteries and veins.  When a tube is cut, we bleed.  Give students an empty cup and a little less than a meter of (3 feet) plastic tubing (approximately 1 cm (½ inch) thick).  The problem is to get the liquid from the head (top) to the toes (bottom). 

    Place the cup with the liquid about 1-3 feet higher than the empty cup.  Have the students siphon the tube so the liquid begins to flow to the bottom cup.  Many students have never seen a siphon, so demonstrate and guide them.  When you suck at one end you are forcing the liquid to flow.  Gravity then continues the flow until no more liquid can flow or no more liquid is left.  Although the tube is open compared to a closed blood network, it does show the students how blood moves.  Students love to "siphon."  
  5. The third part of the lab is for students to see the model heart.  Ask them what the "beating" is all about in their chest.  The heart is the pump that will bring the blood back up so it can circulate through the body.  The model heart  can show students the different parts.  Students can disassemble the heart and put it back. 

    This lab is just to expose students to how blood moves through their body.  Just learning the words "artery" and "vein" will help students to begin to understand circulation.

  6. With a stethoscope, allow the students to hear their heart.  Make sure you clean the ear plugs with alcohol if you have the students share.

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