Chapter 10
The Muscular System
329
10
MUSCLE GALLERY
Table 10.1
Muscles of the Head, Part I: Facial Expression
(Figure 10.7)
The muscles that promote facial expression lie in the scalp and
face just deep to the skin. They are thin and variable in shape and
strength, and adjacent muscles tend to be fused. They are unusual
muscles in that they insert into skin (or other muscles), not bones.
In the scalp, the main muscle is the
epicranius
, which has
distinct anterior and posterior parts. The lateral scalp muscles
are vestigial in humans. Muscles clothing the facial bones lift the
eyebrows, flare the nostrils, open and close the eyes and mouth,
and provide one of the best tools for influencing others—the
smile. The tremendous importance of facial muscles in nonverbal
communication becomes especially clear when they are paralyzed,
as in some stroke victims and in the expressionless “mask” of
patients with Parkinson’s disease.
Cranial nerve VII
, the
facial nerve
, innervates all muscles listed
in this table (see Table 13.2).
Chapter 15 describes the external muscles of the eyes, which
direct the eyeballs, and the levator palpebrae superioris muscles
that raise the eyelids.
MUSCLE
DESCRIPTION
ORIGIN (O) AND
INSERTION (I)
ACTION
NERVE
SUPPLY
MUSCLES OF THE SCALP
Epicranius (occipitofrontalis)
(ep
0
ı˘-kra
9
ne-us;
ok-sip
0
ı˘-to-fron-ta
9
lis)
(
epi
5
over;
cran
5
skull)
Bipartite muscle consisting of the frontal and occipital bellies connected by the epicranial aponeurosis. The
alternate actions of these two muscles pull scalp forward and backward.
Frontal belly
(fron
9
tal)
(
front
5
forehead)
Covers forehead and
dome of skull; no bony
attachments
O—epicranial aponeurosis
I—skin of eyebrows and
root of nose
With aponeurosis fixed,
raises the eyebrows
(as
in surprise). Wrinkles
forehead skin horizontally
Facial nerve (cranial VII)
Occipital belly
(ok-sip
0
ı˘-tal
9
)
(
occipito
5
base of skull)
Overlies posterior occiput;
by pulling on the epicranial
aponeurosis, fixes origin of
frontal belly
O—occipital and
temporal bones
I—epicranial aponeurosis
Fixes aponeurosis and
pulls scalp posteriorly
Facial nerve
MUSCLES OF THE FACE
Corrugator supercilii
(kor
9
ah-ga-ter soo
0
per-sı˘
9
le-i)
(
corrugo
5
wrinkle;
supercilium
5
eyebrow)
Small muscle; activity
associated with that of
orbicularis oculi
O—arch of frontal bone
above nasal bone
I—skin of eyebrow
Draws eyebrows together
and inferiorly;
wrinkles
skin of forehead vertically
(as in frowning)
Facial nerve
Figure 10.7
Lateral view of muscles of the scalp, face, and neck.
(a)
Photograph.
Frontal belly
of epicranius
Corrugator
supercilli
Sternocleidomastoid
(covered by fascia)
Occipital belly
of epicranius
Epicranial
aponeurosis
Platysma
(a)
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