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The skeletal system protects your insides and makes the structure for you to stand. When you were born, you had over 300 bones! Over time, the bones will come together to make one bone. When you are an adult, you will have 206 bones. Bones are hard, but hollow, giving the bones strength. Bones have cells to repair bones and grow. In bones, bone marrow makes blood cells, both red and white. http://yucky.discovery.com/flash/body/pg000124.html

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The Skeletal System (continued)

You have bones to protect vital organs in your body. When you were born, you had over 300 bones. When you are an adult, you will have 206 bones. Bones also provide a structure. Bones are connected to each other by ligaments. The places where bones meet one another are called joints. Also at this point is cartilage. Cartilage is a cushion which helps the bones to not wear down, by making sure they don’t rub together. Bones don’t move by themselves. Muscles help bones and where they connect are called tendons. Marrow in the bones create blood cells.

Fun Facts• Bones would be six times stronger than steel if they were the same weight!• The human hand has 27 bones.• The smallest bone in the body is the size of a rice grain.

Have a healthy diet and stretch before working out.

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Muscles of the Body (continued)

Muscles help move you. You have over 630 muscles in your body, resulting in your body weight being about 40% muscle. The muscles move by muscle cells contracting and relaxing. The muscle cells use chemical energy in food to move. Involuntary muscles do things automatically. Voluntary muscles do things when they are told to. When muscles are pulled, they are torn, but repair themselves.

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The Skin

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The skin is the largest organ in our body. It has three layers. The layers are; the epidermis, the dermis, and the subcutaneous fat. We lose 30,000 to 40,000 dead skin cells every minute. The epidermis makes melanin. Melanin gives skin color. When you are in the sun your skin cells make more melanin to protect you from getting sunburned. Although melanin protects you, you also need sunscreen to prevent skin cancer. The skin forms a protective barrier against germs and other organisms. Your skin also helps you keep a constant body temperature. Human skin is only about 2 mm. thick.

Always wear sunscreen to protect your skin.

The Skin (continued) Skin is the largest organ in your body. Skin protects our bodies and allows us to have

the sense of touch. The skin is made up of three layers; the epidermis, the dermis, and the subcutaneous fat. The epidermis is the top layer where new cells are formed. New cells move up to the top of the skin and the old cells that were at the top die and rise to the surface. We lose about 30,000 to 40,000 dead skin cells every minute of the day. Some of the epidermis makes a substance called melanin, which gives skin its color. The dermis has blood vessels, sweat glands, oil glands, and nerve endings. The dermis works with your brain and nervous system so your brain knows what you’re touching. The oil glands in the dermis makes sebum, which is your skin’s natural oil. Sebum makes your skin waterproof. The subcutaneous fat helps your body stay warm and absorbs shocks. You will also find the start of hair in subcutaneous fat. The hair grows out of follicles. http://kidshealth.org/kid/htbw/skin.html#

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The Nervous System

The nervous system is a complex system, which consists of the brain, spinal cord, and a network of nerves. The nervous system controls everything you do. Nerves send messages to the brain through the spinal cord. The brain receives messages through neurons. When neurons are stimulated they create an electrical pulse. It is divided into two systems, the central nervous system and the peripheral nervous system.

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The nervous system is made up of your spinal cord, your brain, and a huge network of nerves that go throughout your body. It is the central control center for your whole body. Your brain uses information it receives from your nerves to control your actions and reactions. The nerves carry messages back and forth. Sensory nerves send messages to the brain. Then, motor nerves carry messages back from the brain to glands and muscles in your body. When neurons are stimulated by heat, cold, touch, and other things, they begin to make an electrical pulse. This pulse travels on the neuron to the end. At the end of the neuron, chemicals carry the pulse to the next neuron. This keeps happening until neurons have passed the message to the brain or to the muscles and glands in your body. Since the nervous system tells your brain what to do, you couldn’t do a number of things without it. The central nervous system allows you to dream, laugh, write, taste, think, and your heart can’t even beat without it! http://yucky.discovery.com/flash/body/pg000136.html

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When you eat, chemicals in your saliva start chemical reactions. Your teeth chew the food into a wet ball. After a couple of chews, your tongue pushes the chewed food to the back of your throat. Your muscles squeeze the food down your esophagus into your stomach. The esophagus uses muscle movements, called peristalsis, to get the food in your stomach. Your stomach then churns and mixes this food. Food can be in your stomach for 3 to 4 hours. After the stomach, the food goes into the small intestine. The small intestine helps break down the food. Finally, the food travels through the large intestine and exits as feces. http://yucky.discovery.com/flash/body/pg000126.html

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The Digestive System (continued) Digestion allows your body to get nutrients and energy from food. When you eat,

chemicals in your saliva help break down the food. After the food is chewed it goes down your esophagus to your stomach. To make sure that the food enters your esophagus and not your windpipe, which is near it, the epiglottis flops down over your windpipe closing it off from food. Once the food enters the stomach, the stomach breaks it down. Food can be in your stomach for 3 to 4 hours. Gastric juices in the stomach help kill any bacteria that was in the food. Next the food travels into the small intestine, where it is broken down further. From there the food travels through the large intestine where it finally exits the body as feces.

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Drink lots of water to avoid dehydration.

The Circulatory System The circulatory system is made up of the heart,

blood vessels, and blood. The heart pumps blood to every part of your body through blood vessels. The circulatory system is made up of the vessels and muscles that help control the flow of the blood around the body. The main parts of the circulatory system are the heart, arteries, capillaries and veins. When blood begins to circulate, it leaves the heart from the left ventricle and goes into the aorta. The blood leaving the aorta is full of oxygen. Then the blood travels throughout the body. On its way back to the heart, the blood travels through a system of veins. As it reaches the lungs, carbon dioxide is removed from the blood and replaced with fresh oxygen that is inhaled through the lungs. http://library.thinkquest.org/5777/cir1.htm

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The Circulatory System (continued)

The circulatory system includes the heart, blood, and blood vessels. Blood is pumped from your heart to the lungs, where oxygen goes into the blood. The blood with oxygen then travels back to the heart and through the arteries and capillaries to the rest of the body. Veins then carry the blood without oxygen to the heart to repeat this. Red blood cells give oxygen to the cells. The blood that moves from the heart delivers oxygen and nutrients to your entire body. On the return trip, the blood picks up waste products so that your body can get rid of them.

Fun Facts1. If your blood vessels were strung together, they would circle the globe two and a half times!2. The body of an adult contains over 60,000 miles of blood vessels!

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Get plenty of exercise!

The Respiratory System The diaphragm, mouth, lungs, airways,

throat, windpipe, and nasal passages are a part of the respiratory system. The respiratory system helps you breathe. The lungs take in oxygen and then carbon dioxide is breathed out. The oxygen goes throughout the body through blood. There are many diseases that can cause problems with the respiratory system. These include lung cancer, asthma, and tuberculosis. Other problems could be things such as a sore throat. http://42explore.com/respsyst.htm

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The Respiratory System (continued)

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Every living thing needs oxygen to survive. We get oxygen through the respiratory system. The respiratory system includes the mouth, diaphragm, nasal passages, lungs, airways, throat, and the windpipe. It supplies the blood with oxygen when we breathe. We inhale oxygen and exhale carbon dioxide. The air we breathe out has 100 times more carbon dioxide than the air we breathe in.

1. Did you know that when you hiccup, your diaphragm had a spasm? It causes you to breathe in air suddenly.

2. There are about 600 millions air sacs in your lungs. If they were stretched out, they would cover a tennis court!

3. Irritations in the upper airway is what causes you to sneeze.

The heart is a muscle. It’s about the size of your fist. What do our hearts do? Our hearts send blood around our bodies. The right side of the heart receives blood from the body and then pumps it to the lungs. The left side is different. It receives blood from the lungs and pumps it to the body. The heart fills with blood and contracts. It contracts to squeeze out the blood. The heart has four different chambers. There are two chambers on each side of the heart. Two chambers are on the top and two chambers on the bottom. The two chambers on top are called the atria. Only one chamber is called an atrium. The atria are the chambers that fill with blood returning to the heart from the body and lungs. The heart has a left atrium and a right atrium. The two chambers on the bottom are called the right and left ventricles. They squirt out the blood to the body and lungs. Your body needs a steady supply of blood to keep it working. http://kidshealth.org/kid/htbw/heart.html#

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Exercise on a regular basis and eat healthy.

The Heart (continued)

The heart is a muscle about the size of a fist and it keeps the blood pumping through our bodies. It contracts and relaxes to squirt out blood. The blood in our bodies circulate through the heart. The heart has four chambers; the top chambers are the atria and the bottom chambers are the ventricles. The atria and ventricles work as a team. The atria fill with blood, then dump blood into the ventricles. The ventricles then squeeze, pumping blood out of the heart. While the ventricles are squeezing, the atria refill and get ready to start the process over again.

Fun FactsA woman’s heart beats faster than a man’s.The human heart weighs less than a pound.The human heart can create enough pressure so that it could squirt blood to a distance of thirty feet. In a lifetime, the heart pumps about one million barrels of blood. In one day, your heart beats 100,000 times. 

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Cartilage: A type of connective tissue.Neurons: Threads of nerve cells that make an electrical pulse.Esophagus: The tube that carries food from the throat to the

stomach.Air Sac: Air sacs hold the air in the lungs.Marrow: Fatty network of connective tissue in bones.