muscles of facial expression slides(1)

7/27/2019 Muscles of Facial Expression Slides(1)

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Muscles of Facial

Expression

Muscles of Facial

ExpressionAlex Forrest

Associate Professor of Forensic OdontologyForensic Science Research & Innovation Centre, Griffith University

Consultant Forensic Odontologist,

Queensland Health Forensic and Scientific Services,

39 Kessels Rd, Coopers Plains, Queensland, Australia 4108

Oral Biology


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Learning ObjectivesLearning Objectives

You should be able to explain the embryological origin of

the muscles of facial expression, and to explain the

resulting common motor nerve and blood supply

You should be able to explain how the muscles of facial

expression are classified.


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Learning ObjectivesLearning Objectives

You should be able to demonstrate knowledge of the

principal functions of the major groups of muscles offacial expression in normal function.

You should be able to relate your understanding of

muscle functions to origins and insertions.


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Facial StructureFacial Structure

The basic form of the face is determined largely by the

underlying bony structures. These are covered by the soft

tissues which comprise muscles, subcutaneous fat and

other components.In some areas of the face, there is very little subcutaneous

soft tissue. These areas include the upper part of the nose,

the margins around the orbits, the forehead, and the areaover the zygomatic arches, and around the lower border of

the mandible.


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The bone can be palpated through the skin in these

areas, and as a result the skin tends to be relativelyimmobile in these regions.

Try this out on your own face (or that of a friend)

now



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Other regions in the face are separated from theunderlying bone by larger amounts of subcutaneous

tissue.

As a consequence, these areas tend to be more mobilewhen acted on by muscles, and are largely responsible for

the facial expressions.

These soft tissues are moved by a group of muscles

which is therefore called the subcutaneous muscles of

facial expression.


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ClassificationClassification

This muscle group shares a common nerve supply; all

motor supply to them comes from the facial nerve (VII).

You will recall that the facial nerve arises from the hyoid

arch or second branchial arch, and that the muscles of

facial expression, including the platysma, are derived fromthis arch as well.


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You should note that not all the muscles supplied by VII are

classified as muscles of facial expression.

Specifically, the stylohyoid muscle and the posterior belly of

the digastric muscle are not included in this group,

although they are derived from the muscle element of the

2nd arch.


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Other muscles also play a part in determining facialexpression, including the hypoglossal nerve (XII) (sticking

the tongue out) and the oculomotor nerve (III) (rolling the

eyes) but they are not classified in this group either.


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Most muscles of facial expression have a bony origin and

insert into the soft tissue of the face.

Some have variations on this theme. The buccinator

originates from the pterygomandibular raphe, for

instance, and the orbicularis oris has no bony attachment

at all.


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The muscles of facial expression can be classified into groups:

Muscles of the lips and cheeks

Muscles of the nose

Muscles of the eyelid

Muscles of the auricle of the ear

Muscles of the scalp

Platysma muscle


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Muscles of the

Lips and Cheeks

Muscles of the

Lips and Cheeks


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Lips and CheeksLips and Cheeks

The muscles of the lips and cheeks are divided into two layers:

Superficial muscles

Deep muscles


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Superficial Layer:

Levator labii superioris alaquae nasi

Levator labii superioris

Levator anguli oris

Zygomaticus major & minor

Risorius

Depressor labii inferioris

Depressor anguli oris

Mentalis


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Deep Layer:

Buccinator

Orbicularis oris


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Levator labii superiorisLevator anguli oris


Risorius



Mentalis

Superficial Layer:

Grays Anatomy, Longman, London, 35th Edition, 1973. p 496.


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Van De Graff, K. Human Anatomy, Iowa, Wm. C. Brown, 2nd Ed., 1988. p. 246


Levator labii superiorisLevator anguli oris


Risorius



Mentalis

Superficial Layer:



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The muscles of thesuperficial layer

converge on lips and

enter them in a radial

distribution.

They originate on the

maxilla and mandible,

on the zygomaticbones, and from the

masseteric fascia.



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Mandible, External Surface

Grays

Anatomy,

Longman,

London, 35th

Edition, 1973.p. 281.



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Zygomatic Bone, Lateral Aspect

Grays

Anatomy,

Longman,

London, 35th

Edition, 1973.p. 309.



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Many of these

superficial musclesconverge to insert on a

vertical

musculotendinous

raphe close to thecorner of the mouth.

This is known as the

modiolus, and is visible

through the skin as a

surface feature on the

face.

Lockhart RD, Living Anatomy. London, Faber & Faber 7th Ed. 1974, p. 16



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Orbicularis OrisOrbicularis Oris

The fibres of

orbicularis orisform a kind of

sphincter around

and within the

lips.



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A small number of fibres attach to the maxilla and mandible in

the area associated with the sockets of the incisors (frenula).

Some fibres insert into the modiolus, while others insert on the

deep surfaces of the skin and mucous membrane of the mouth.

University of Queensland School of Dentistry 2001


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Contraction of its fibres

draws the lips together,and tight contraction

causes pursing of the lips

as in pouting or whistling.

The lips are parted by

relaxation of the orbicularis

oris with simultaneous

contraction of the maxillaryand mandibular radiating

muscles.

Van De Graff, K. Human Anatomy, Iowa, Wm. C. Brown, 2nd Ed., 1988. p. 247


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BuccinatorBuccinator

The buccinator

muscle lies deep

within the cheeks andis closely related to

the buccal mucous

membrane.



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Posteriorly it attaches

to the

pterygomandibular

raphe.Superiorly it attaches

to the alveolar process

of the maxilla, andbelow to that of the

mandible.

Modified from: Grays Anatomy, Longman, London,

35th Edition, 1973. p 499.


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Anteriorly its deeper fibres insert into the modiolus, and

the superficial ones insert into orbicularis oris.

Many of its fibres decussate prior to insertion to

strengthen the angle of the mouth.


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NoseNose

No detail need be known


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Orbit & EyelidOrbit & Eyelid

Each eyelid is given a degree of rigidity by a dense fibrous

structure, the tarsal plate.



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The principal muscle of the eyelid region is the orbicularis

oculi. This comprises an orbital part, which overlies the bone

surrounding the orbital cavities, and a palpebral part which

is situated within the eyelids.



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Both parts are attached to the medial palpebral ligaments at

the medial corners of the orbits, and to the adjacent bones.

Clemente CD, Anatomy, A Regional Atlas of the Human

Body, Munich, Urban & Shwarzenberg, 1975, Diagram 485.


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The orbital fibres radiate

around the orbits. They

insert into the overlying

skin.

The palpebral fibres insert

into the skin of the eyelids

and into the tarsal plateand lateral palpebral

ligament.

Grays Anatomy, Longman, London, 35th Edition,1973. p 496.


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The palpebral fibres ofthe orbicularis oculi close

the eyelids gently, as in

sleeping.

The orbital fibres draw

the eyebrows down as in

frowning, and help

forcibly close the eyes,as in an expression of

agony.

Grays Anatomy, Longman, London, 35th Edition,

1973. p 496.


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AuricleAuricle

No detail need be known


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ScalpScalp

The scalp consists of five layers. From superficial to deep,

these are:

S Skin

C Connective Tissue

A Aponeurosis

L Loose Connective Tissue

P Periosteum


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ScalpScalp

The epicranial

aponeurosis is atendinous sheet into which

the frontalis muscle

attaches anteriorly, and

the occipitalis muscleattaches posteriorly.

At the side of the skull, the

aponeurosis unites withthe underlying temporal

fascia.




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ScalpScalp

The aponeurosis is looselyattached to the underlying

periosteum, so some

movement is permitted.

The American Indians

used to take advantage of

this loose connection in

the process of scalpingtheir victims.




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ScalpScalp

The fibres of the frontalisattach to bone in the

region of the root of the

nose via fibres that are

known as the procerus

muscle.

Its intermediate fibres

insert on the skin of theeyebrows and forehead.




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ScalpScalp

The occipitalis attaches to the superior nuchal lines of the

temporalis muscle.

Together, the frontalis and occipitalis muscles can move

the aponeurosis and the overlying skin, but the amount of

movement varies between individuals.


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In the LabIn the Lab

As you study these structures, you will find that virtually all

textbooks referring to the anatomy of the head and neckcontain diagrams of these muscles to a greater or lesser

extent.


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In the LabIn the Lab

You should take the opportunity to examine skulls during

your practical sessions in detail.Feel the bones with your fingers. Can you feel

roughnesses in the bone surface in the places you expect

the muscles to attach?


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The End

muscles of facial expression slides(1)

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