Topic: Locomotion
Aim: Use textual evidence to describe the functions of the skeletal system.
Directions: Read the passage below. Use textual evidence to answer questions 1 - 11.
Your skeleton is an elegant system of over two hundred bones throughout your body. The bones are connected by
ligaments and moved by muscles to which they are connected by tendons. The largest bone in your body is the femur, or thigh
bone. Your smallest bone is in your inner ear. It is called the stapes. All of the bones, from the big femur to the tiny stapes,
weigh a lot! An adult skeleton makes up about one-fifth of that person’s total body weight.
How many bones does a human have? This is a hard question to answer, because the number varies. Your skeleton
changes throughout your lifetime. A newborn baby has about 300 bones, while an average adult has only about 206 bones. This
is because some bones fuse, or grow together, as you get older. Some of the bones you are born with have pockets of cartilage
between them so you can grow. By the time you are between 13 and 18, there are no more pockets of cartilage, and your
skeleton is finished growing.
Cartilage is a flexible connective tissue in animals, including the joints between bones, the rib cage, the ear, the nose, the
bronchial tubes and the intervertebral discs. It is not as hard and rigid as bone, but it is stiffer and less flexible than muscle.
Functions of your skeleton include support, protection, attachment, movement, blood cell production, and storage. It
holds us up and protects our internal organs. Without a skeleton, most animals, including humans, would be a shapeless pile
of limp muscles. The skull protects the brain, the ribcage protects the heart and lungs, and so on. Your bones are a point
where muscles, tendons, and ligaments are attached in the body. Vertebrates use their skeletons to move. The bone marrow, the
inside of the bone, is where all blood cells are produced. The skeleton also stores mineral nutrients, especially calcium.
Calcium is stored in the bones, and taken out when you don’t have enough calcium in your diet. This is why it is so important to
get enough calcium in your diet, because if too much calcium is removed from the bones, this can cause osteoporosis, which
makes the bones weak and brittle.
1. How many bones does a human skeleton have? ______________________________________________________
2. Why do adults have fewer bones than a baby? ____________________________________________________________
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3. Identify the tissues that connect bones together. ________________________________________
4. Identify the tissues that connect muscles to bones. _______________________________________________
5. Identify where cartilage is found. ________________________________________________________________________
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6. Describe the physical characteristics of cartilage. ___________________________________________________________
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7. Describe how the skeletal system supports the body. _________________________________________________________
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8. Describe how the skeletal system provides protection. _______________________________________________________
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9. Describe how the skeletal system is involved in blood cell production. ___________________________________________
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10. Describe how the skeletal system is involved in storage. ______________________________________________________
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11. Why is it important to have enough calcium in your diet?
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