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THE SKELETAL AND MUSCULAR SYSTEM
Chapter 15.1
Bones and Joints
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OBJECTIVES
Describe the structure and function of bones Explain the roles of joints and muscles in
movement Contrast skeletal, cardiac and smooth
muscles Describe some disorders of bones, joints, and
muscles
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KEY TERMS
Joint Ligament Tendon Flexor Extensor Osteoporosis Arthritis
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THE SKELETON IS MADE OF BONES
There are 206 bones in the adult body Calcium Phosphate is the mineral that makes bones hard The toughness of bone gives the body
strength Bones are not rigidly connected to each other
Exception: the bones of your skull
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BONES ARE MADE OF LIVING CELLS
Bones contain blood vessels and nerves The blood carries nutrients to and wastes away
from the bone cells Many bones have a spongy interior called marrow
which produces blood cells The main function of bones are to:
Allow movement, support the body, and protect internal organs
The picture shows an osteocyte
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JOINTS CONNECT DIFFERENT BONES
• A place where two or more bones are connected is a joint
• There are several types of joint:– Fixed joints connecting the skull plates– Pivot joints like your elbow– Hinge joints like your knee– Ball and socket joints like you shoulder– Gliding joints like your fingers or toes– Saddle joint like your thumb
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LIGAMENTS
Moveable joints do not hold bones tightly together
Flexible but strong straps of tissue hold the bones tightly togetherLigaments
connect bone to bone
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MUSCLES
• There are three types of muscle:– Cardiac
• Found only in the heart
– Skeletal, (move in pairs)• Attach to two or more
bones– Flexor– Extensor
– Smooth• Found in the bladder
and digestive system
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MUSCLES AND FORCE
Bones need muscles to allow them to move
Tendons are the attachment point for muscles to bones
Muscles must be anchored to more than one bone to allow for movement
Muscles work in pairs to flex and extend the bone through the range of motion of the joint
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MUSCLES AND NERVE SIGNALS
Muscles contract due to nerve signals
Muscles relax after the signal has passed
Sometimes muscles contract without YOU having to think about it Breathing Blinking
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DISORDERS OF THE BONES, JOINTS, AND MUSCLES
Osteoporosis is a bone disorder
Bones can “break” when under stress Osteocytes or “bone
cells” can heal a broken bone given time
A fracture or break causes bone cells to fill in the gap
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JOINT DISEASE
Arthritis causes pain by the ends of bone rubbing together at the joint
The smooth covering is worn away and the bones begin to show signs of damage
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SPRAINS AND STRAINS OF LIGAMENTS
The picture is of a sprained elbow, notice the joint is displaced
Ligaments, tendons, and muscles may all become damaged by the displacement
Muscles repair first, then tendons, then ligaments, (if at all)
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SUMMARY
Bones are living tissue. They produce blood cells, allow movement,
support the body, and protect internal organs Bones move when skeletal muscles contract
in response to chemical signals from the brain and spinal cord
Dietary calcium and certain types of exercise can strengthen bones
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DEFINITIONS
A joint is a place where two or more bones meet
A ligament is a strong strap of body tissue that holds the bones of a joint in place
A tendon is a strong cord of body tissue that connects skeletal muscle to bone
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DEFINITIONS
A flexor muscle is a muscle that decreases the angle between two bones
An extensor is a muscle that increases the angle between two bones
Osteoporosis is a bone disorder in which the bone becomes less dense and more fragile
Arthritis is a condition in which the joints become swollen and painful