Chapter 16:
The Bones and Soft Tissues
Function of the
Skeletal System
 Aids in movement
 Supports and protects internal
organs
 Produces red and white blood cells
 Stores minerals
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Long Bone Anatomy
 The structure of bones in the body
allows them to be both lightweight
and strong.
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Structure of Long Bone
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Cartilage
Red marrow
Spongy bone
Medullary cavity
Artery
Compact bone
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Structure of Long Bone
(cont.)
 Endosteum
 Yellow marrow
 Periosteum
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Fractures
 Fractures are classified based on
the various characteristics of the
broken bone.
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Fracture Types
 Simple (closed) fracture: no skin
penetration
– Complete
• Two separate pieces
• Comminuted: three or more pieces
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Fracture Types (cont.)
 Simple (closed) fracture: no skin
penetration
– Incomplete
• Greenstick: in children with flexible
bones
• Stress: due to overuse, weakness,
biomechanical problems
• Epiphyseal plate: young people
near growth plate
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Fracture Types (cont.)
 Compound (open) fracture:
skin penetrated
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Muscle Action
 Most skeletal muscles work in
groups to accomplish a smooth,
coordinated action.
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Moving the Skeleton
 Prime mover: A muscle that is a
major contributor to a particular
movement, such as the biceps
brachii for arm flexion. (The strong
brachialis muscle could also be
considered a prime mover of arm
flexion.)
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Moving the Skeleton (cont.)
 Antagonist: A muscle that is a major
contributor to the opposite
movement of a prime mover, such
as the triceps brachii (which causes
arm extension).
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Moving the Skeleton (cont.)
 Synergists: Muscles that work
together with a prime mover to help
it produce a smooth, steady
movement, such as the
brachioradialis helping the biceps
brachii during arm flexion.
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Moving the Skeleton (cont.)
 The role of a particular muscle
(prime mover, antagonist, synergist)
will likely change for different
skeletal joint movements.
 For example, the biceps brachii is a
prime mover for arm flexion, but it is
an antagonist for arm extension, for
which the triceps brachii is the
prime mover.
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Muscle Stimulation
 Muscles are controlled by
stimulation from neurons of the
nervous system.
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Control of Contraction
 The signal to contract a muscle
begins with neurons in the brain or
spinal cord, which communicate
with other neurons that ultimately
reach the neuromuscular junction.
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Control of Contraction (cont.)
 Dendrites carry signals toward the
cell body, and the axon (one per
neuron) carries signals away from
the cell body toward other neurons,
muscles, or glands.
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Control of Contraction (cont.)
 Though there is only one axon per
neuron, most axons branch at some
point and can stimulate several
other neurons or muscle cells at the
same time.
 Many axons, but not all, are
surrounded by insulating Schwann
cells, which also allow for faster
transmission of the nerve signal.
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The Nerve Impulse
 The normal, resting nerve cell
(neuron) maintains an unequal
distribution of electrical charge from
the inside (negative) of the cell to
the outside (positive).
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The Nerve Impulse (cont.)
 A nerve impulse is a change in the
neuron’s membrane, due to a
series of ion movements, that
makes the outside negative and the
inside positive.
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The Nerve Impulse (cont.)
 When the impulse passes (it can
travel the complete length of the
neuron), the membrane returns to
its normal resting state. In other
words, it repolarizes.
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