1. Did you know that babies are born with a total of 350 bones? An adult only has about 206 of them! As they grow and age, a baby's bones fuse together. Bones must be made of living tissue in order to grow and change. The skeletal system is made of all the bones in the human body. A skeletons rock-like bones are no longer alive. All the bones in your body, however, are still alive. In fact, each bone is a living organ, made of several different tissues. The cells in bones act in the same way as other body cells. They absorb nutrients and expend energy. Healthy bones are dense and strong.
2. The skeletal system has five major functions. First, bones act like the internal wooden structure of a house. Bones are the framework that supports your body. They also give your body its shape. Second, bones protect your delicate internal organs. For example, ribs surround the heart and lungs. A skull protects the brain. Third, major muscles attach to the bone and make them move. Fourth, blood cells are actually formed in the red marrow of some bones. Marrow is the soft tissue in the center of many bones. Both red and white cells are made there. We cannot live without them. Red blood cells take oxygen to all parts of the body. White blood cells fight off germs and diseases. Finally, calcium and phosphorus make bone hard. The skeleton is the place where calcium and phosphorous are stored for later use.
3. Bone is made of living tissue, which explains why a broken bone actually heals. To remain alive, the bone cells need blood. The bone is fed by the blood, which also removes its waste. Deep inside a compact bone are the Haversian systems, also known as circular structures. Did you know that you can actually see these systems in a cut bone? They look like the rings of a cut tree trunk. Also, bones are not as smooth as you might think. Instead, they are full of pits, rough spots, bumps, and edges. Without these spots, muscles would not be able to attach to the bone. There are also holes that allow blood vessels and nerve endings into the bone.
4. You can usually tell a bones function by its shape. Can you guess what the longest bone is in your body? It is the femur - the thigh bone. It is actually one-quarter of your height! Deep within the ear, you will find the smallest bone, the stirrup bone. It is usually about one-tenth of an inch long. Another interesting fact is that bones adapt to the functions they perform. Bone shapes are genetically controlled. They will, however, be modified by the work done by the muscle.
5. There are over 230 moveable and semi-moveable joints in the body. A semi-moveable joint allows little or no movement. These are seen with the bones of the skull. A moveable joint makes a flexible connection between bones. The body needs joints with flexibility to allow the body to move back and forth. This is easily seen with the knee. The knee joints work like door hinges, allowing you to move your leg back and forth. Still other joints allow twisting, such as in the neck, so you can turn your head. You also have shoulder joints, which allow the arm bone to move nearly full circle.
6. Cartilage is a thick smooth layer of cushiony tissue. Cartilage is usually found at the ends of the bones. It does not contain blood vessels or minerals. As people age, cartilage sometimes wears out. This causes the common painful condition known as arthritis. Each time a person moves, they feel intense pain.
7. Without the skeletal system, we would be like a human beanbag. We would flop around like one big puddle of skin and organs. Our flexible skeletal system allows us to stand and walk, bend and rotate, and work against the forces of gravity.Which sentence would the author disagree with?
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15 points
Bones adapt to the functions they perform.
Flexible skeletal system provides mobility and purpose for our body.
Each bone is a non-living organ comprised of several different tissues.
Bone shapes are genetically controlled and routinely modified depending upon the work performed by the muscle.
The sentence that the author would disagree with is "Each bone is a non-living organ comprised of several different tissues." The author states that each bone is a living organ, made of several different tissues.
he skeletal system has many functions. Which of the following body functions does the skeletal system not do?
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15 points
Remove germs from the blood
Protect the internal organs
Give shape and support to the body
Produce red and white blood cells