Blood Cells

Contributor: Hannah Brooks. Lesson ID: 12627

What was blood created for? It does more than gross you out; it heals, clots, feeds cells, destroys enemies -- it's like a hospital, diner, and army all in one! Find out how amazing this red stuff is!


Life Science

learning style
personality style
Grade Level
Middle School (6-8)
Lesson Type
Dig Deeper

Lesson Plan - Get It!


Blood looks like a liquid, similar to water and milk, but did you know it is made up of individual cells working together?

Blood is one of the most important fluids in your body, because it supplies oxygen to your limbs and ensures that each body system has the nutrients it needs to function properly.

Blood is made up of four parts: plasma, white blood cells, red blood cells, and platelets.

Before continuing, if you missed or need to review the first lesson in this Human Body Cells series, check it out under Related Lessons in the right-hand sidebar.

Plasma is not a type of cell; rather, it is the watery material that the red and white blood cells travel through. It contains small amounts of sugar, fat, protein, and salts, nutrients that are distributed throughout your body. When your blood is separated based on each component, plasma moves to the top and has a white-yellow color.

White blood cells, or leukocytes, are special immune system cells that help fight off foreign invaders, including bacterial, viral, fungal, and other cells that may cause infection. They make up a very small percentage of your total blood cell count. White blood cells are produced inside your bone marrow and move freely through your blood; they can build up after an injury to help promote healing. If your white blood cell count is high, it may mean you have an infection somewhere in your body.

Another reason an individual can have an elevated white blood cell count is cancer. Certain blood-based cancers, like leukemia, can increase the number of white blood cells in order to fight off dividing cancer cells in the blood. This rapid division can actually lead to an increase in the cancer cells found in the blood, allowing the cancer to spread rapidly.

White blood cells contain a nucleus and can have different structures to assist with the specifc role they play in immunity. For example, some white blood cells are phagocytes, or cells that ingest. This means they engulf the invader and digest it with special chemicals.

Red blood cells give blood the dark red color, and make up nearly half of the blood. They have a unique shape: a disc that contains a depression on each side. Think about two mixing bowls stacked with the flat bottoms touching in the middle — that is the shape of a red blood cell.

Red blood cells are responsible for carrying oxygen throughout the body. They use a special protein, called "hemoglobin," that allows oxygen to attach to the cell and be transported through the blood effectively. Red blood cells are produced in the bone marrow and are released into the bloodstream for use. They do not have a nucleus, which allows them to bend and move freely through tight passageways in the body.

There are some disorders that affect red blood cells, like sickle cell anemia. Individuals with sickle cell anemia have red blood cells that are misshapen, making it harder for them to pass through small passageways. This can cause symptoms like mucus buildup and respiratory issues. Sickle cell can be treated with medication and therapy, but it can cause patients significant discomfort.

Finally, platelets make up the remainder of your blood. These are not true cells, but small pieces of cells that combine together to seal injuries. Platelets assist in the process of coagulation, where blood cells join together to create a sticky mass that prevents blood leakage. Coagulation is what occurs when a cut stops bleeding!

You need all four components of blood in order to have the circulatory system functioning properly. Red blood cells ensure that your body receives oxygen, while white blood cells fight off infection and keep you healthy. Plasma is responsible for moving each component of blood smoothly, and platelets allow you to heal injuries and prevent excessive bleeding.

  • What do you think would happen if your blood were out of balance?
  • Have you ever heard of low white blood cell count?

Discuss what you have learned with a parent or teacher before moving to the Got It? section, where you will learn more about red and white blood cells.

Elephango's Philosophy

We help prepare learners for a future that cannot yet be defined. They must be ready for change, willing to learn and able to think critically. Elephango is designed to create lifelong learners who are ready for that rapidly changing future.