You have four main types of tissues: epithelial, nervous, muscle, and connective tissue. Epithelial tissue covers the outside of the body. It also lines organs and cavities. Nervous tissue sends electrical signals. Muscle tissue helps you move. Connective tissue joins bones and cushions organs.
When groups of tissues work together, they are called organs. Some
examples of organs are the heart, lungs, skin, and stomach. When organs work together, they are called systems. For example, your heart, lungs, blood, and blood vessels work together. They make up the circulatory system.
There are eleven systems in the human body: muscular system, respiratory system, digestive system, integumentary system (skin), skeletal system, circulatory (or cardiovascular) system, excretory (or urinary) system, reproductive system, nervous system, lymphatic system, and endocrine system. Each system has a special job.
All of your body systems have to work together to keep you healthy. Your bones and muscles work together to support and move your body. Your respiratory system takes in oxygen from the air. It also gets rid of carbon dioxide.
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Your digestive system absorbs water and nutrients from the food you eat.
Your circulatory system carries oxygen, water, and nutrients to cells throughout your body. Wastes from the cells are eliminated by your respiratory system, your excretory system, and your skin. Your nervous system controls all these activities with electrical impulses. If any system in your body isn't working properly, other systems are affected.
Think of your body as a building. A building has a plumbing system, a heating system, a cooling system, an electrical system, and a support system. If any system in a building breaks down, other systems can be affected.
As one example, think about a building's electrical system. Suppose a mouse chewed through an electrical wire to a furnace. Without electricity, the heating system would not work. If this happened in very cold weather, the plumbing system could be affected. Water pipes might freeze and burst. If a lot of water leaked into the building's walls, its support system would be damaged. Like a building's systems, your body's systems have to work together.
