Science 4
Lesson 1
NAME: _______________________________ SCORE: ____________________________
Human Body
The Skeletal System
The human skeleton is a complex connection of small and large bones that has several
major functions:
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It protects our vital organs such as the brain, the heart, and lungs.
It gives us our structure and shape and supports the body’s weight...
It allows our bodies to be flexible since muscles are attached to our bones.
At birth, you have a collection of about 350 bones, but due to the process of fusion over
time caused by growth of your body, you will have about 206 bones by the time you are
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an adult.
In order for our bones to move different ways, we have joints that connect one to the
other. At the end of each bone is a substance called cartilage which is a tough, smooth,
flexible connective tissue that allows bones to move over each other easily. Between
the cartilages is synovial fluid which is a lubricant that allows for greater movement. This
is especially important in people who are competitive in sports.
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Inside a Bone
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They have their own nerves and blood vessels, and they do various jobs, such as
storing body minerals.
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A typical bone has an outer layer of hard or compact bone, which is very strong, dense
and tough. Inside this is a layer of spongy bone, which is lightweight. In the centre of the
bone is the bone marrow with contains both red and yellow marrow.
The yellow marrow is a fatty tissue and the re marrow is where the blood cells are
produced. The marrow is critical, especially to those who are ill with cancer and need
another person to donate their bone marrow in order to survive.
Bone Count:
Skull and upper jaw 21 bones
3 tiny bones in each ear
Lower jaw (mandible)
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Front neck bone (hyoid)
Backbone or spine (26 separate bones or vertebrae)
Ribs (12 pairs - same number for men and women)
Breastbone
Each upper limb has 32 bones: 2 in shoulder, 3 in arms, 8 in wrist, 19 in hand
and fingers.
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Each lower limb has 31 bones: 1 in hip (one side of pelvis), 4 in leg, 7 in ankle,
19 in foot and toes.
The Human Skeleton
Examine all bones that comprise our skeleton. When you are comfortable with the
names, fill in the diagram on the next page with the names. Try to do this without
looking back.
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Breaking a bone
Bones contain living cells that help them grow longer and stronger as you grow. If you
break a bone, the cells repair the damage and the bone fixes itself. Sometimes a doctor
sets the broken bones in the hard cast to prevent it from moving and causing further
damage. This helps the bone repair in the correct position. Doctors take x-rays several
times during the repair to ensure that the body has fully healed. Below is an x-ray of a
broken bone. Can you tell what part of the body it is? (Hint: hand)
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1. Define the following terms:
a) Skeleton:
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b) Joints:
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c) Marrow:
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d) Cartilage:
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2. Name 3 vital organs that the skeleton protects?
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3. Explain why you have more bones when you are born:
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Critical Thinking:
Why do you think there are a series of very small connecting bones in the hands and
feet? Explain what your theory is.
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