Kids' Guide to Human Body Systems

The human body isn't just one big system, it is actually made up of many different separate systems, all working together to make sure that you, as a whole, function correctly. Each system has special parts and functions that it has to perform in order to keep you healthy and well. If any of the separate systems stops working or doesn't work like it should, the whole body will suffer. Learning about different body systems will help you know what you need to do to stay healthy and strong.

Immune System

Your immune system is in charge of keeping you healthy. It guards the body to keep germs from invading. With a healthy immune system, the body will be strong enough to fight against germs and infections. If germs do get into the body, the immune system attacks them to try to keep you from getting sick. White blood cells are the attackers that find germs and work to destroy them.

Muscular System

The human body is full of muscles. In fact, you have more than 600 different muscles throughout your body. Muscles help you move, but also have other important jobs. Your heart is a muscle, and its job is to pump blood all through your body. The body contains three different kinds of muscles - smooth, skeletal, and cardiac. The cardiac muscle is your heart muscle. Smooth muscles are the muscles that move without you telling them to move. Some of these muscles are in your digestive and urinary systems. Skeletal muscles are the muscles that you control. These are the muscles you use to run, climb, and jump.

Digestive System

Your digestive system is in charge of handling all the food you eat. This system is very involved, starting at your mouth and extending all the way out to the end of your large intestine. Digestion is the process of breaking down food so your body can use it for energy and nutrients. As food passes through the digestive tract, the body absorbs the nutrients it needs. Anything the body does not need is eliminated through the excretory system.

Respiratory System

The lungs are a big part of the respiratory system. Sitting in your chest, the rib cage covers the lungs to help keep them safe from injuries. The diaphragm sits just under the lungs, and it works with them to help you breathe air in and out of the body. When you breathe air into the lungs, tiny alveoli become full of air. The alveoli are in charge of moving oxygen from inhaled air into the bloodstream, where oxygen will reach all parts of the body. The blood also carries carbon dioxide back to the alveoli, where the lungs get rid of it when you exhale.

Nervous System

The nervous system includes the brain and the spinal cord. You could think of your brain as a powerful computer that is in charge of everything your body does, inside and outside. The brain controls all of your muscles, both voluntary and involuntary ones, to keep the body functioning. The cerebrum part of the brain is the part you use when you listen to your teachers to learn about history or science. Parts of the brain are also in charge of how you grow and even for keeping your body at the right temperature. The spinal cord has very fragile bundles of nerves running through it, which are responsible for helping you move and giving you feelings throughout your body.

Skeletal System

Your skeletal system is made up of all the bones in your body. Bones have several layers of tissues that work together to keep them nourished and strong. In the very center of bones, bone marrow that looks like jelly works to make new blood cells. When you were born, you had about 300 bones in your body. As you grow up, some of these bones will grow together. By the time you are an adult, you will have only 206 bones.

Endocrine System

The endocrine system is in charge of managing the chemical processes that happen in the body. Some of these processes include how you grow, your moods, and how your body uses energy. The endocrine system uses hormones to send instructions to cells. Different hormones communicate with different cells, depending on the work performed by the cells.

Cardiovascular System

The cardiovascular system includes the circulatory system and the heart. As the heart pumps blood, the circulatory system is in charge of moving the blood throughout the body. Blood moves in blood vessels called veins, arteries, and capillaries. The blood carries oxygen to cells and tissues, and then it carries carbon dioxide and waste so the body can get rid of it.

Excretory System

As the various systems in your body work, they produce waste. These chemicals need to be removed from the body, or they could make you very sick. The kidneys are in charge of filtering blood to remove urea, which is a waste product. After the kidneys collect the urea, they move it to the bladder for removal from the body. The intestines process food so the body can use the nutrients it needs. The parts of the food that the body doesn't need get moved through the intestines until the body excretes them.

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