Attached to the sternum, clavicle,
and mastoid process.
Located near the outside, with f
that run obliquely or in a slanting direction.
Muscles of Facial Expression
A number oF small muscles beneath the skin oF the Face
and scalp enable us to communicate Feelings through Facial
expression. Many oF these muscles are located around the
eyes and mouth, and they make possible such expressions as
surprise, sadness, anger, Fear, disgust, and pain. As a group,
the muscles oF Facial expression connect the bones oF the
skull to connective tissue in regions oF the overlying skin.
movements depend upon the antagonists’ relaxing and giv-
ing way to the prime movers whenever the prime movers
contract. Once again, the nervous system coordinates these
complex actions, as described in chapter 11 (p. 410).
Sometimes the relationship between two muscles
changes. ±or example, the pectoralis major and latissimus
dorsi are antagonistic For ﬂ
exion and extension oF the shoul-
der. However, they are synergistic For medial rotation oF the
shoulder. Thus, the role oF a muscle must be learned in the
context oF a particular movement.
The movements termed “f
exion” and “extension” describe changes
in the angle between bones that meet at a joint. For example, f
o± the elbow joint re±ers to a movement o± the ±orearm that decreases
the angle at the elbow joint. Alternatively, one could say that f
ion at the elbow results ±rom the action o± the biceps brachii on the
radius o± the ±orearm.
nd it help±ul to think o± movements in terms o± the
speci±ic actions o± the muscles involved, so we may also describe
exion and extension in these terms. Thus, the action o± the biceps
brachii may be described as “f
exion o± the ±orearm at the elbow” and
the action o± the quadriceps group as “extension o± the leg at the
knee.” We believe that this occasional departure ±rom strict anatomi-
cal terminology eases understanding and learning.
Explain how parts o± the upper limb ±orm a ²
rst-class lever and a
Distinguish between the origin and the insertion o± a muscle.
ne prime mover.
What is the ±unction o± a synergist? An antagonist?
MAJOR SKELETAL MUSCLES
This section discusses the locations, actions, origins, and
insertions oF some oF the major skeletal muscles. The tables
that summarize the inFormation concerning groups oF these
muscles also include the names oF nerves that supply the
individual muscles in each group. Chapter 11 (pp. 414–423)
presents the origins and pathways oF these nerves.
show the locations oF superf cial
skeletal muscles—that is, those near the surFace. The names
oF muscles oFten describe them. A name may indicate a mus-
cle’s size, shape, location, action, number oF attachments, or
the direction oF its f
bers, as in the Following examples:
A muscle oF large size (major) in the
pectoral region (chest).
Shaped like a delta or triangle.
Extends the digits (f
ngers or toes).
A muscle with two heads (biceps), or
points oF origin, in the brachium (arm).
Anterior view o± super²
cial skeletal muscles.