Captions are on! Click "CC" at bottom right to turn off. Follow the amoebas on Twitter (@amoebasisters) + Facebook! Have you ever heard the phrase, “I know this like I know the back of my hand!” Well it may make you question…do you really know the back of your hand? Because if you look at your hand you see your skin but it’s also what you can’t see underneath your skin that’s pretty incredible. You can’t see the millions of cells that make up your hand. At least, not without a microscope. We take those cells for granted sometimes, but your body is made up of millions of cells!! Cells that work together. Cells that are very organized with specific functions. Cells that all carry your whole DNA code, but use specific parts of your DNA code depending on the cell’s function. Your cells make up body tissues. . Tissues make up organs, like your heart for example. And organs are part of an organ system like your circulatory system. Organ systems are so important for you to understand in order to know how your body works. One thing to keep in mind is that organ systems do not work in isolation. They are not loners. They work together and are part of a big team. We’re going to intro the 11 major organ systems. Keep in mind this is just a quick intro so we’re doing the bare bones (no pun intended) of the systems. Because they are all important, it’s hard to know where to start! So we’re going to go in alphabetical order, because we don’t want you to think that one is way more important than another. First---the circulatory system. You think of blood and you should, because blood carries gases like oxygen (which your body needs) and helps remove CO2 (which your body needs to expel). Your blood also transports nutrients that your body needs. Your heart is included in this system. It is a pumping machine that transports the blood around. Arteries are vessels that typically carry blood away from the heart (think “a” for away), veins typically carry blood back to the heart, and capillaries are tiny blood vessels throughout your body. Did you ever hear the rumor that your blood is blue and then turns red when it reaches oxygen? Guess what---that’s not really true. Your blood is red---and always red even inside your body---though the shade of red can vary slightly due to the amount of oxygen present. Veins may appear blue—or even green---to you through the skin but it’s actually related to wavelengths of light (to the google!) Second- the digestive system. It is important for breaking down and absorbing food for your body to get nutrients. Digestion actually starts in the mouth----you have some awesome enzymes in your saliva that get the process going. Your stomach contains acid to further this process. Your small intestine does most of the absorption of nutrients and your large intestine has to reabsorb a lot of the water from this process. This is a fascinating process and there are a lot of accessory organs involved in this system too. Third- the endocrine system. You know how you’re bigger than you were when you were six years old? Growth hormone is a hormone that’s made a big impact on you. Notice how your heart starts to race when you have a big test that you haven’t studied for? That’s another hormone----adrenaline for you. The endocrine system includes many glands that secrete hormones. Another system that starts with “e” is #4, excretory. I like to think “exit” for excretory because this system is all about excreting wastes. I’m not talking about feces because that’s still digestive. More like urine. This system involves your kidneys (lower back). The kidneys assist in removing wastes from the blood. You know they’re important because anyone with impaired kidneys may need to go on a machine called dialysis to replace that function. The excretory system also includes other ways of removing waste, like sweating. Ok #5, integumentary. Long fancy word is appropriate for your largest organ----your skin. Your skin helps protect your organs from outside damage, helps with temperature regulation, and from losing precious water. #6 Lymphatic/Immune System. Has anyone ever checked your lymph nodes on your neck when you feel sick? You have many lymph nodes and they tend to swell during some illnesses. See---lymph is this clear fluid from blood plasma that surrounds cells. This system collects, filters, and returns the lymph to the blood and a major role is to help with immune function. This keeps your body safe against pathogens like viruses and bacteria. Structures like lymph nodes, the thymus, spleen, tonsils, and bone marrow play significant roles in your immune system. Ok more than halfway done with our intro---hang in there. #7- Muscular System- No bones about it---your bones can’t do much without muscle to move them. You have three major types of muscle tissue known as skeletal, smooth, and cardiac muscle. #8- Nervous System- Your body would be a nervous wreck without something to coordinate it. This always helps me remember the nervous system. The nervous system includes your brain and your spinal cord---it controls voluntary actions (that’s what you can control like picking up your pencil) with involuntary actions---ones you don’t control (reflexes are an example of this). At the cellular level, the nervous system uses cells known as neurons. With their amazing structure, these cells are kind of the cool cells on the block. #9- Reproductive system- Like it sounds, this system includes reproductive organs. The major function here that it allows for animals to reproduce. Think: babies. #10- Respiratory System- Involves the lungs---this system involves the intake of oxygen into the body and exhaling carbon dioxide from the body. Remember that your body cells need this oxygen---and they need to get rid of carbon dioxide---in order to function correctly. #11- The skeletal system. Bones. Adults have 206 bones---you have more at birth but some bones fuse together----and these bones support you, protect your organs (think: ribcage), and even produce blood cells from the bone marrow that is inside the bone. Understanding how the human body works is fascinating---and it’s necessary so that we can figure out what to do when things go wrong. There are doctors that specialize specifically with each of these systems. The most amazing part to us though is their beauty in how they work together----working every second to let you do the things that you do. Want an example? Let’s say that---when the bell rings at the end of the day---that you were to race your friend down the hall. Think of all the body systems interacting for that to happen. Your respiratory system is going to increase its breathing rate---and that extra oxygen is going to be delivered through the circulatory system to your body tissues. Your muscles are interacting with the skeletal system for movement. These are just some interactions of the systems working together for that example. The human body----is just truly a magnificent masterpiece. That’s it for the amoeba sisters and we remind you to stay curious.