Chapter 16: The Bones and Soft Tissues. Copyright ©2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 2 Function of the Skeletal System Aids in movement

Chapter 16:

The Bones and Soft Tissues

Copyright ©2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 2

Function of the Skeletal System

Aids in movement Supports and protects internal

organs Produces red and white blood cells Stores minerals


Long Bone Anatomy

The structure of bones in the body allows them to be both lightweight and strong.


Structure of Long Bone

Cartilage Red marrow Spongy bone Medullary cavity Artery Compact bone


Structure of Long Bone (cont.)

Endosteum Yellow marrow Periosteum


Fractures

Fractures are classified based on the various characteristics of the broken bone.


Fracture Types

Simple (closed) fracture: no skin penetration– Complete

• Two separate pieces• Comminuted: three or more pieces


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


Fracture Types (cont.)

Compound (open) fracture: skin penetrated


Muscle Action

Most skeletal muscles work in groups to accomplish a smooth, coordinated action.


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.)


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).



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.



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.


Muscle Stimulation

Muscles are controlled by stimulation from neurons of the nervous system.


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.


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.


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.


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).


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.


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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Chapter 16: The Bones and Soft Tissues. Copyright ©2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 2 Function of the Skeletal System Aids in movement