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The Human Body Lesson The skeleton is a living thing. There are 206 bones in your body. (unless you had an accident with some power tools.) Babies have about 350 bones when they are born. They are made of cartilage and haven’t grown together yet. There are 4 types of bones; long, short, flat, irregular. Long- femur, humerus,radius, ulna. Short-carpals, tarsals Flat-cranium, ribs, sternum Irregular- vertebrae, sacrum, coccyx. These are the catacombs of Paris where millions of people’s remains can be found lining the walls. There are actually two skeletons inside of you. The Axial Skeleton is the skeleton you must have to live. Your chest and cranium. The Appendicular Skeleton is made of bones and limbs you can live without. Your arms, legs, hands, feet. After 911, more than 1300 soldiers have lost limbs during combat. New advances in prosthetics are always needed. Tendons are strong, cords that connect the muscle to bone. Ligaments are tough, rubberband-like tissue that connect bones to other bones. Marrow is the soft tissue inside of bones that make blood cells. It produces about 5 billion red blood cells a day! Ligaments connect bones to other bones. I’m sorry to say that there is no such thing as “double-jointed.” I know, let me guess, you know someone who can bend their arm or finger, or elbow really weird. Sorry, they still aren’t double jointed. These people only have longer tendons and ligaments either naturally or from stretching them over time. The outer walls of bones are made of a dense tissue called compact bone. The inside of bones is made of a softer tissue called spongy bone. Spongy bone’s more scientific name is “Cancellous Bone” A joint is a place where two bones meet. There are five movable joints and one nonmoving joint. Your skull has a special joint called a fixed joint. The bones are locked in place and do not move. Ball and Socket These allow circular movement. Found in your shoulders and hips. Hinge joints allow movement in one direction. Found in your elbows and knees. Pivot This joint is found only in your neck. Allows you to look up, down, side to side. Gliding(Sliding) Bones slide on a disc of cartilage. Found in your backbone. Saddle Allows movement in two directions. Found in your thumb. She can do this because of the gliding joints in her back. The longest bone is your femur. The smallest is the stirrup found in your ear. Dislocated Bones are bones that have been knocked out of place. Owie! Fractures are breaks in bones. Simple Fractures are cracked bones. Compound Fractures are when the bone breaks but then pushes through the skin. DOUBLE OWIE!