The fifth lesson that I covered in an A&P unit for younger children dealt with blood. Previous lessons centered on the skeletal system, the central nervous system, the respiratory system, and the cardiovascular system. Our lesson on blood tied in well with the latter, and provided some review.
Activities:
- Read the book A Drop of Blood by Paul Showers, illustrated by Edward Miller. This book was recommended for an older age group than what my children are, but with several breaks for discussion and explanation, they remained engaged.
- Reviewed the pages on the heart, blood and circulation in our book Eye Wonder: Human Body. The book has some very nice microscopic photographs of cells, the interior of the heart, the inside view of an artery, capillary networks and so on.
- Completed a short project to demonstrate how bruises are injuries where blood vessels break and blood leaks out and can be seen where it collects beneath the skin. I came upon this project on the site Our Time to Learn in a post about injuries. We adapted the project somewhat to use materials we had on hand: paper towels, straws, food coloring and water. I traced the kids' hands and forearms onto paper towels, placing a second paper towel beneath each one. Next, I cut our straws into shorter pieces and added red and blue food coloring to water to create a blood-colored liquid. I carefully put the liquid into the straws and laid each straw piece between the prepared layers of paper towels. The kids then hit the straws, causing the liquid to shoot out and create what looks like a bruise on the hand and arm. We had a few trials - getting enough liquid in the straws and getting it to stay there until being hit was a bit tricky. But overall, the kids understood the concept of how a bruise is formed.
- Made a model of blood, based on the post "What's Inside a Drop of Blood" by Creekside Learning. For this model, we again went with what we had on hand, as well as adding an element to represent fibrin. As we added blood components, I also had the kids draw a diagram of the components onto their mini whiteboards, using differing colors of dry erase markers for each component. Our steps used in creating this model are shown in the following slideshow.
- Items used: corn syrup, dry lentils, red cinnamon candies, white poker chips, white string, bowl, mini whiteboard with various colored markers
Discussion points:
- Blood has four main components - plasma, red blood cells, white blood cells, and platelets.
- Plasma makes up more than half of our blood (55%), and is a clear, light yellow liquid which transports the other components as well as many other substances that our bodies needs.
- Red blood cells (RBC's) make up a large portion of our blood (45%) and carry oxygen to and carbon dioxide away from our cells. The RBC's are small and are red-colored due to having hemoglobin, which is red-colored and contains iron.
- White blood cells (WBC's) make up a very small portion or our blood (<1%) but are very important in fighting off germs, bacteria and viruses. When people are sick, their bodies release more WBC's. The WBC's are larger than RBC's, and there are several different types.
- Platelets are small, sticky cells that help to form clots when there is an injury that causes bleeding. They also comprise a small portion of our blood (<1%). Platelets are assisted in their clot-forming job by fibrin, a thread-like substance that helps the clot stay together.
- Blood also carries other things that our bodies need to function properly - like nutrients, proteins, and hormones - as well as wastes that our bodies need to dispose of.
- Bruises, also called contusions, occur when small blood vessels break due to being bumped. Blood escapes from the blood vessel and collects under the skin, forming the coloration of a bruise. A bruise will change colors as it heals.
- If a person is injured and loses too much blood, they can die. However, when people lose blood from injuries or operations, some of their blood can be replaced by blood donated by other people. This is how someone can help to save a life by donating their blood (though they have to be a healthy, old enough and big enough to donate). Blood donation involves taking blood from one person using a needle and tube and putting that blood into another person, after the blood has been checked and received special treatments. When a person donates blood only a small amount is taken, so the donor will still be okay.
- Since blood carries so many substances needed and released by our bodies, it can indicate a lot about a person's health. Sometimes, a doctor may order a blood test so that a person's blood can be checked to ensure they are healthy. During a blood test, a needle is inserted in to a blood vessel to withdraw a very small amount of blood. It might sound scary, but it doesn't hurt very much, doesn't last very long and is often necessary to make sure a person is healthy.
Vocabulary words:
- Plasma, red blood cells, white blood cells, platelets, fibrin, contusion, blood donation, blood test
Additional activities (which we didn't do this time, but I'd like to do sometime in the future):
- Watch a video about blood donation, such as this one by Florida's Blood Centers.
- Explain the different blood types (A, B, AB, O).
Resources:
- KidsHealth provides an explanation of blood, along with a video about what is involved when getting a blood test.
- The Women and Children's Health Network in South Australia has a Child and Youth Health page that provides good kid-friendly information about blood.
- Easy Science for Kids has a succinct explanation of blood and a drawing indicating what percent of blood is comprised by each component.