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Body Systems Your body is made of many different parts. Some of these parts work together to get certain jobs done. These groups are called body systems. Each system is made of many organs all working together to do an important job. Respiratory System It is used for breathing in oxygen and breathing out carbon dioxide. The oxygen enters through your nose and mouth, travels down your trachea, and into your lungs. The lungs have many fragile little air sacks called alveoli which pass the oxygen into your blood. The alveoli also pass the carbon dioxide out of your blood and into your lungs. The carbon dioxide then travels back up your trachea and out of your mouth and nose. Breathing in pollution, smoke, or chemicals damages the lungs. Your brain automatically moves your diaphragm to make you breath in and out, respiration. Circulatory System It is used for transporting nutrients and waste around your body. It is made of blood, vessels, and a pump. The pump is called the heart and is used to push the blood through the vessels to every cell in your body. There are big vessels called arteries which take blood from the heart, and veins which take blood back to your heart. There are small vessels called capillaries which link your cells to the arteries and veins. On the way to and from the heart the blood passes through many organs which clean out waste and pick up nutrients. Digestive System It is used for turning food and water into energy and nutrients. As the food passes through the digestive system it is mixed with substances which break it down. First it is chewed in the mouth and passed through the oesophagus and duodenum into the stomach. Strong acid in the stomach breaks the food right down into mush. The mush then passes into the small intestine where the nutrients are extracted and passed into the blood. The mush then passes into the large intestine where all the water is removed. The waste is then removed from the body through the anus. Your intestines are full of bacteria which help extract the nutrients and break down the food. Skeletal System It is used for keeping our body stable, strong, and usable. It is also used for keeping all our organs in the correct places. It is made of bones which are connected by joints and tendons. The bones are made of calcium and can break easily. Bone marrow creates our red and white blood cells. An adult has 206 bones, an infant has 300 bones. RL Body Systems 10/06/2008