Download Human Head, Neck, Eye muscles

Human Head and Eye
muscles
Epicranius (frontalis), Levator labii superioris,
Orbicularis oculi, Orbicularis oris, Buccinator, Masseter,
Zygomaticus, Temporalis
1
3
2
6
7
5
6
4
Epicranius
Orbicularis
oculi
Temporalis
Levator
labii
superioris
Zygomaticus
Buccinator
Masseter
Orbicularis
oris
Buccinator
Massetor
What muscles were damaged?
Smiling
• The French neurologist, Duchenne du Boulogne, writing in the
nineteenth century, made a fundamental discovery about the nature
of smiling, a discovery that was forgotten for a hundred years.
Duchenne electrically stimulated different positions on the face of a
patient who had no pain sensation, and photographed the resulting
expressions. By this means he learned how the different facial
muscles produced different expressions. He showed that the
zygomatic major muscle, which runs from the cheek bone down to
the lip corners, pulls those lip corners upwards into a smiling shape
(Fig. 1). Importantly, Duchenne noted that the man in this picture did
not really look happy. He told him a joke, and noted that, when the
man smiled spontaneously, it involved not just the zygomatic major,
but part of a second muscle, the orbicularis oculi, which encircles
the eye (Fig. 2). Duchenne noted that this is a muscle that most
people cannot contract voluntarily, and so it ‘unmasks the false
friend’.
Smiling
• In 1982, Paul Ekman resurrected Duchenne's distinction to explain
why people often smile when they are not happy. As Duchenne had
noted, Ekman found that people who smile when they are not feeling
enjoyment do not show activity of the muscle around the eyes, just
the lip muscle. Many studies now support Duchenne's distinction
between these two types of smiling — what scientists now call, in
honour of Duchenne, Duchenne smiles, or D-smiles for short
(zygomatic major outer part, and orbicularis oculi) and non D-smiles
( zygomatic major only). For example, 5-month-old infants show Dsmiles when approached by their mother, non D-smile when
approached by a stranger. In adults the D-smile is accompanied by
the pattern of brain activity found with enjoyment, but that brain
activity pattern is not found when the non D-smile is shown. Happily
married couples show D-smiles when they meet at the end of the
day, while unhappily married couples show non D-smiles.
Smiling
Non-Duchenne smile
Duchenne smile
Smiling
•
•
It is not always easy to distinguish these two types of smiles. If the lips are
pulled only slightly or moderately by the zygomatic major muscle, it is easy
to see whether the eye muscle is involved, for it will produce crow's feet
wrinkles and bagging of the skin under the eyes. Those signs are absent in
a slight to moderate non D-smile. However, when the smile is very broad,
the lip pulling itself will produce those changes in the face and it is
necessary to look elsewhere. Only in the D-Smile will the eyebrows move
down ever so slightly.
Instead of signalling genuine enjoyment, non D-smiles serve many different
social functions. They may indicate agreement, they show a person is
willing to go along with something, even something unpleasant (grin and
bear it), and they may also be used to send a false message of enjoyment
when none is felt. Research has shown that most people do not notice the
difference between D-smiles and non D-smiles, and it is hard not to
reciprocate a smile, even a non-D smile.
Superior, Inferior, Medial, Lateral rectus,
Superior, Inferior oblique
Superior rectus
Superior oblique
Lateral rectus
Medial rectus
Inferior Oblique
Superior oblique
Inferior rectus
Lateral rectus
Superior rectus
Name
Name
Name
Name
Name
Superior rectus
Lateral rectus
Inferior Oblique
NOTE: This is
NOT the model
in our lab. This is
a RIGHT eye.
Medial rectus
Inferior rectus
Name
Name
Name
Name
Superior rectus
Superior Oblique
Lateral rectus
Medial rectus
Name
Name
Name
Superior rectus
Lateral rectus
Inferior Oblique
Medial rectus
NOTE: This is
the model in
our lab. This is
a left eye.
Lateral rectus
Inferior oblique
NOTE: This is
the model in
our lab. This is
a left eye.
Lateral rectus
Inferior oblique