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Guide to the Human Body Systems

by Dr. Sam Muslin

The human body is comprised of several different systems. They work together to ensure that you can move, eat, and breathe. Each system has its own set of parts, each one with a different job. Learning more about some of the different human body systems means learning more about how you work and what is going on inside your own body every day.

Circulatory System

You need to keep blood moving to every part of your body at all times. The circulatory system makes sure this happens, carrying nutrients and oxygen all around your body. Made up of the heart, blood vessels, and your blood, the circulatory system is always working. If you put your hand on your chest or your wrist, you'll feel your pulse, proof that your circulatory system is hard at work.

Respiratory System

If you're breathing, your respiratory system is getting its job done! Your airways and lungs are just a few parts of this system. There are actually a lot of smaller pieces, including the bronchioles and the trachea, that make sure that oxygen makes its way into your body. The respiratory system works with the circulatory system to get oxygen to all of your body and then helps get rid of the carbon dioxide the body doesn't need.

  • Your Respiratory System: This article provides lots of information on how the respiratory system works along with a diagram of the different parts.
  • Clean Air, Healthy Children: A Teacher's Guide and Activities for Young Children (PDF): In addition to useful information about the respiratory system, this document tells how air pollution can affect your body and cause problems.
  • How the Body Uses O2: Where does oxygen go once it heads into the lungs? Learn more about what happens to the oxygen and how it travels through the body.
  • Your Lungs: Full of pictures, vocabulary words, and information, this site helps you understand how your lungs work and explains more about asthma, an illness that makes it hard for your lungs to work properly, and what it feels like.

Immune System

No one likes being sick. Your immune system helps prevent you from getting sick and fights off infections when you get them. This system is the body's defense from everything from a cold to different types of diseases. Your white blood cells are an important part of the system, as they seek out germs and attack them.

Skeletal System

Without the skeletal system, you'd probably be just a great big pile of mush! The bones work to give the body its shape and help you move. An adult body is made up of more than 200 bones, all working together to help keep the body stable and upright. Your teeth are also part of the skeletal system.

  • Skeletal System Photos and Diagrams: This site offers lots of detailed photos and diagrams that look at this part of the human body. Take the quiz to see just how much you know.
  • Living Bones, Strong Bones (PDF): NASA helps students take a closer look at bones with this lesson plan, which looks at what happens to astronauts' bones in space and why strong bones matter.
  • "Them Not-So-Dry Bones": Watch this Schoolhouse Rock! video to learn about your bones.
  • Help Mr. Bones! (PDF): Print this out and put the skeletal system back together.

Excretory System

Just like taking the trash out when it is full, the human body also has a process for getting rid of waste. While the teeth may be one of the first things that come into contact with food, they certainly aren't the last. Getting rid of waste is actually a very important part of keeping the body healthy, and that's what the excretory system does.

  • Human Excretory System (PDF): These workbook pages offer a diagram of the system, an explanation of each of the parts, and questions for kids to consider.
  • Worksheets on the Excretory System (PDF): From vocabulary activities to fill-in-the-blank sentences, you can learn more about the excretory system and the urinary system with these activities. You can also build a kidney to learn about and show how it works.
  • The Excretory System (slide show): With lots of information along with a diagram, this slide show offers an easy-to-understand explanation of how the system works.
  • Why Is Excretion Necessary for Life? Learn about waste needs to be removed from the body and how it happens.

Urinary System

The urinary system gives the body another way to get rid of waste. Made up of organs including the kidneys and the bladder, the urinary system helps the body to get rid of water and other things that it the body doesn't need. If this part of the body isn't working, it could cause a buildup of waste that could make you sick.

Muscular System

If you are moving, your muscles are working. The muscular system uses skeletal, smooth, and cardiac muscles to take care of the body. Lots of the organs involved in the other systems are actually muscles! Whether you are breathing, running, or even digesting food, the muscular system is getting the job done.

  • The Muscles Required to Run: This diagram shows two bodies and all of their muscles, how they are attached, and how they move.
  • Muscle Tissue: Check out these slides that show different types of muscles that are found in the human body.
  • The Muscular System (PDF): Learn about three types of muscles and their different functions with this lesson plan. At the end of the lesson, students can build a clay muscle chart.
  • What Is the Strongest Muscle in the Human Body? This question doesn't have one simple answer, but you can learn a lot about some of the muscles that work the hardest here.

Endocrine System

There are lots of glands that make up the endocrine system. This system helps you grow and even has an effect on your mood and how you sleep. Many of the parts have interesting names, like the hypothalamus and the thyroid, and they all use different chemicals inside of your body to do their jobs. Without these parts, the body wouldn't be able to do lots of important things, including turning you from a kid into an adult.

  • The Endocrine System: An Influential Part of the Human Body (PDF): Every cell and organ of the body depends on the endocrine system to regulate important things like your mood, development, and even how the rest of your body functions. This diagram shows the different parts of the system.
  • The Endocrine System: Who Is in Control Here? (PDF): Glands and hormones work inside the human body in a variety of different ways. This lesson helps students understand the science behind things like emotions and puberty.
  • Introduction to the Endocrine System: Check out this video that discusses the endocrine system and the types of hormones in the body.
  • Endocrine Disorders Activity: What happens when the endocrine system isn't working properly? After learning more about a patient, you can diagnose the problem, learning more about the system as a whole along the way.