306
UNIT TWO
Figure 9.25
and reference plate 66 show these muscles, and
table 9.3
lists them. The muscles of facial expression include
the following:
Epicranius
Zygomaticus major
Orbicularis oculi
Zygomaticus minor
Orbicularis oris
Platysma
Buccinator
The
epicranius
(ep
ı
˘-kra
ne-us) covers the upper part of
the cranium and consists of two muscular parts—the
fron-
talis
(frun-ta
lis), which lies over the frontal bone, and the
occipitalis
(ok-sip
ı˘-ta
lis), which lies over the occipital bone.
These muscles are united by a broad, tendinous membrane
called the
epicranial aponeurosis,
which covers the cranium
like a cap. Contraction of the epicranius raises the eyebrows
and horizontally wrinkles the skin of the forehead, as when
a person expresses surprise. Headaches often result from
sustained contraction of this muscle.
The
orbicularis oculi
(or-bik
u-la-rus ok
u-li) is a ring-
like band of muscle, called a
sphincter muscle,
that surrounds
the eye. It lies in the subcutaneous tissue of the eyelid and
closes or blinks the eye. At the same time, it compresses the
nearby tear gland, or
lacrimal gland,
aiding the fl ow of tears
over the surface of the eye. Contraction of the orbicularis
oculi also causes the folds, or crow’s feet, that radiate later-
ally from the corner of the eye. The muscles that move the
eye are described in chapter 12 (pp. 464–465).
The
orbicularis oris
(or-bik
u-la-rus o
ris) is a sphinc-
ter muscle that encircles the mouth. It lies between the skin
and the mucous membranes of the lips, extending upward to
the nose and downward to the region between the lower lip
and chin. The orbicularis oris is sometimes called the kissing
muscle because it closes and puckers the lips.
The
buccinator
(buk
sı˘-na
tor) is located in the wall of
the cheek. Its F bers are directed forward from the bones of the
jaws to the angle of the mouth, and when they contract,
the cheek is compressed inward. This action helps hold food
in contact with the teeth when a person is chewing. The buc-
cinator also aids in blowing air out of the mouth, and for this
reason, it is sometimes called the trumpeter muscle.
The
zygomaticus
(zi
go-mat
ik-us)
major
and
minor
extend from the zygomatic arch downward to the corner of
the mouth. When they contract, the corner of the mouth is
drawn upward, as in smiling or laughing.
Gracilis
Rhomboid
Latissimus
dorsi
Infraspinatus
External
oblique
Gluteus medius
Adductor
magnus
Vastus lateralis
Sartorius
Soleus
Fibularis longus
Brachialis
Temporalis
Occipitalis
Semimembranosus
Sternocleidomastoid
Trapezius
Teres minor
Teres major
Triceps
brachii
Biceps femoris
Semitendinosus
Gastrocnemius
Calcaneal tendon
Gluteus
maximus
Deltoid
FIGURE 9.24
Posterior view of superF
cial skeletal muscles.
TABLE
9.3
|
Muscles of Facial Expression
Muscle
Origin
Insertion
Action
Nerve Supply
Epicranius
Occipital bone
Skin and muscles around eye
Raises eyebrow as when surprised
±acial n.
Orbicularis oculi
Maxillary and frontal bones
Skin around eye
Closes eye as in blinking
±acial n.
Orbicularis oris
Muscles near the mouth
Skin of central lip
Closes lips, protrudes lips as for kissing
±acial n.
Buccinator
Outer surfaces of maxilla and mandible
Orbicularis oris
Compresses cheeks inward as when blowing air
±acial n.
Zygomaticus major
Zygomatic bone
Corner of mouth
Raises corner of mouth as when smiling
±acial n.
Zygomaticus minor
Zygomatic bone
Corner of mouth
Raises corner of mouth as when smiling
±acial n.
Platysma
±ascia in upper chest
Lower border of mandible
Draws angle of mouth downward as when pouting
±acial n.
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