Chapter 8
Lesson 2 The Skeletal System
Bones and Joints
•
Bones A bone is an organ of the skeletal system.
Bones are hard because they store minerals.
•
Bone Marrow Inside a bone is soft tissue called
bone marrow. Bone marrow makes blood cells for
the body.
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Joints
• Joints A joint is a place where two or more
bones meet.
• Joints – where bones meet to allow
movement
– Sliding joints – allow bones in hand to
glide over one another
– Ball-and-socket joint – enables you arm
or leg to move freely in all directions
– Hinge joint – enables you to flex and
extend elbow and knee.
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• Ligaments attach bones to
another bone at the joint.
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Chapter 8
Lesson 2 The Skeletal System
Bone and Joint Development
•
Cartilage Before birth, most of the bones in a
baby’s body are made of cartilage. Cartilage is a
soft, flexible tissue.
•
Bone Formation Cartilage starts changing to bone
before a baby is born. The soft tissue hardens and
becomes bone tissue as minerals, such as calcium,
build up in the bone. This change is not finished
until a person is around 18 years old.
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How the Skeletal System Works
Label the Skeletal System
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Chapter 8
Lesson 3 The Muscular System
Many Kinds of Muscles
•
Skeletal Muscle Skeletal muscle is muscle that is
attached to bones. Example: Bicep
•
Smooth Muscle Smooth muscle is muscle that
forms some internal organs. Example: Small
Intestine
•
Cardiac Muscle Cardiac muscle is muscle that
forms the heart.
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Chapter 8
Lesson 3 The Muscular System
Muscles and Movement
•
How Muscles Move Bones When skeletal
muscles contract, they pull on bones. When a
muscle contracts, its two ends are pulled towards
its center. If the two ends are attached to different
bones, the bones are pulled towards each other.
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Chapter 8
Lesson 3 The Muscular System
Muscles work in pairs. Here, the biceps and triceps
move the bones of the arm by pulling them in
opposite directions.
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Chapter 8
Tendons attach a muscle to a bone at the
joint.
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Chapter 8
How the Muscular System
Works
Label the Muscular System
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