171
Lesson
Before You Read
Try to answer the following questions before you read
this lesson.
What muscles are responsible for breathing?
What important functions do the neck and
trunk muscles contribute beyond movement
capabilities?
What are the primary functions of the lower
limb?
There are more than 650 skeletal muscles in
the human body. In this lesson we will present only
the most important muscles from the standpoint
of functional movement. Almost all of these
muscles are arranged in agonist-antagonist pairs,
causing opposing actions at one or more joints.
Directional Motions
To understand the functional movement of
muscles, you need to learn a new concept about
muscle attachments. It will also be helpful to
review some directional terms that you learned
in chapter 1.
Skeletal muscles attach at either end of
the muscle; the most common attachments are
tendon connections to bone. The end of a muscle
that attaches to a relatively fi xed structure is
called the origin. The end of a muscle that
attaches to a bone that typically moves when the
muscle contracts is called the insertion.
For an example of origin and insertion, let’s
look at the brachialis muscle, which crosses the
anterior side of the elbow. Its origin is on the
humerus, and its insertion is on the ulna in the
forearm. When the brachialis contracts, the forearm
(ulna) is pulled toward the upper arm, while the
upper arm (humerus) remains stationary.
Remember—when stimulated to develop
tension, muscles can only pull. They are
incapable of pushing.
In addition, remember from chapter 1 that to
describe the human body and its movements, we
refer to three major planes that pass through the
center of the body:
• The sagittal plane is in line with forward and
backward motions;
• The frontal plane is in line with sideways
movement; and
5.3
The Major The Major
Skeletal MusclesMuscles Skeletal
Lesson Objectives
1. Describe and give examples of the types
of body motions that occur in the sagittal,
frontal, and transverse planes.
2. Identify the locations and functions of the
muscles of the head and neck.
3. Identify the locations and functions of the
trunk muscles.
4. Identify the locations and functions of the
muscles of the upper limb.
5. Identify the locations and functions of the
muscles of the lower limb.
Key Terms
abduction
adduction
circumduction
dorsifl exion
eversion
extension
fl exion
hyperextension
insertion
inversion
lateral rotation
medial rotation
opposition
origin
plantar fl exion
pronation
radial deviation
supination
ulnar deviation
E-Flash Cards