1. Skull, Neck and
Muscles
Ritesh shiwakoti
MScD Prosthodontics
1st year 2nd semester
2. Skull
Contains 22 bones
Rest superior to the
vertebral column
Consists 2 sets of bones,
facial and cranial bones
Cranial bones forms the
cranial cavity, which
encloses and protect the
brain
Facial bones form the face.
3. Cranial Bones (8 bones)
1 Frontal bone
2 parietal bones
2 temporal bones
1 Occipital bone
1 Sphenoid bone
1 Ethmoid bone
8. Function of the skull
Protect the brain
Inner surface attach to the membranes
(meninges) that stabilize the position of the brain,
blood vessels and nerves.
Outer surface of cranial bones provide large areas
for muscle attachment that move various part of
the head.
The bones also provide muscle attachment for
some muscles that produce facial expressions.
9. Function of the skull
Facial bones – forms framework of the face
Facial bones – provide support for entrance to the
digestive and respiratory system
Together cranial and facial bones protect and
support the delicate special sense organs for vision,
taste, smell, hearing and equibilirium.
10.
11. Frontal Bones
Forms the forehead, the roof of the orbits
and most of the anterior part of the cranial
floor
Soon after birth, the left and right side of
the frontal bone united together by the
metopic suture, usually disappear by age
of six to eight.
12.
13.
14. Frontal Bones
Frontal Bone that forms the forehead – Frontal
squama
Superior to the orbits the frontal bone thickens,
forming the supraorbital margin.
From this margin, the frontal bone extends
posteriorly to form the roof of the orbits, which is part
of the floor of the cranial cavity.
Within the supraorbital margin, slightly medial to its
midpoint, is a hole called supraorbital foramen where
supraorbital nerve and artery pass through it.
15. Frontal Bones
Frontal sinuses lie deep to the frontal
squama.
Sinuses, or called parasinuses, are
mucous membrane – lined cavities in
certain skull bones.
17. Parietal Bones
2 parietal bones
Form the greater portion of the side and
roof of the cranial cavity
Internal surface of parietal bones contain
many protrusion and depression that
accommodate the blood vessels supplying
the dura mater (superficial connective
tissue that lining the brain.
Two foramina in the parietal bones.
18.
19. Temporal Bones
2 temporal bones
Form the inferior lateral aspects of the
cranium and part of the cranial floor
Lateral view of the temporal bones, called
temporal squama, the thin, flat part that form
the anterior and superior part of the temple.
Projecting from the inferior portion of the
temporal squama is the zygomatic process.
22. Temporal Bone
Zygomatic process of temporal bones
articulate with temporal process of zygomatic
(cheek) bone form the zygomatic arch
A socket called the mandibular fossa is
located on the inferior posterior surface of the
zygomatic process of the temporal bones.
Anterior to the mandibular fossa is a rounded
elevation called articular tubercle.
23.
24. Temporal Bone
The mandibular fossa and articular tubercle
articulate with the mandible (lower jawbone)
to form the temporomandibular joint (TMJ).
Located posteriorly on the temporal bone is
the mastoid portion.
It is located posterior and inferior to the
external auditory meatus or ear canal.
25. Temporal Bone
The mastoid process is a rounded projection
of the mastoid portion of the temporal bone
posterior to the external auditory meatus.
It is the point for several neck muscles
attachment.
The internal auditory meatus is the opening
through which facial nerve (cranial nerve VII)
and vestibulocochlear nerve (cranial nerve
VIII) passes.
26. Temporal Bone
The styloid process projects inferiorly from
the inferior surface of the temporal bones
and serve as a point of attachment for
muscles and ligaments of the tongue a neck.
Between the styloid process and mastoid
process is the stylomastoid foramen.
28. Temporal Bone
At the floor of the cranial cavity is the
petrous portion of the temporal bone.
This part is the triangular and it is located
at the base of the skull between the
sphenoid and occipital bones.
The petrous portion houses the internal
and middle ear, structure involve hearing
and equibilirium.
29. Temporal Bone
It also contain the carotid foramen,
through which the carotid artery passes.
Posterior to the carotid foramen and
anterior to the occipital bone is the jugular
foramen, passageway for the jugular vein.
30. Occipital Bone
Forms the posterior part and most of the
base of the cranium
The foramen magnum is in the inferior
part of the bone.
Within this foramen, the medulla
oblongata connect with the spinal cord.
The vertebral and spinal arteries also
pass through this foramen.
31.
32. Occipital Bone
The occipital condyles are oval processes
with convex surface, one on either side of the
foramen magnum.
They articulates with depression on the 1st
cervical vertebra (atlas) to form the atlanto-occipital
joint.
Superior to each occipital condyle on the
inferior surface of the skull is the hypoglossal
foramen.
33.
34. Occipital Bone
The external occipital protuberance is a
prominent midline projection on the
posterior surface of the bone just above the
foramen magnum.
A large fibrous, elastic ligament, the
ligamentum nuchae, which help support the
head, extend from the external occipital
protuberance to the 7th cervical vertebra.
35.
36. Occipital Bone
Extending laterally from the protuberance
are two curved ridges, the superior nuchal
lines, and below these are two inferior
nuchal lines, which is areas for the
muscles attachment.
37. Sphenoid Bone
Lies at the middle part of the base of the
skull.
Keystone of the cranial floor because it
articulates with all the other cranial bones,
holding them together
Sphenoid articulation – joins anteriorly with
the frontal bone, laterally with the temporal
bones and posteriorly with the occipital
bones.
39. Sphenoid Bone
Lie posterior and slightly superior to the
nasal cavity and forms part of the floor, side
walls, and rear wall of the orbit.
The shape of the sphenoid resembles a bat
with outstretched wings.
The body of the sphenoid is the cube-like
medial portion between the ethmoid and
occipital bones.
42. Sphenoid Bone
It contains the sphenoidal sinuses, which
drain into the nasal cavity.
The sella turcica, ia bony saddle-shaped
structure on the superior surface of the body
of the sphenoid.
Anterior part of the sella turcica, which form
the horn of the saddle, is a ridge called the
tuberculum sellae.
43. Sphenoid Bone
The seat of the saddle is a depression,
called hypophyseal fossa, which contain
pituitary gland.
The posterior part of the sella turcica, which
forms the back of the saddle, is another ridge
called the dorsum sellae.
The greater wings of the sphenoid project
laterally from the body and form the
anterolateral floor of the cranium.
44.
45. Sphenoid Bone
The greater wings also form part of the
lateral wall of the skull just anterior to the
temporal bone.
The lesser wings, which are smaller, form a
ridge of bone anterior and superior to the
greater wings.
They form part of the floor of the cranium
and the posterior part of the orbit of the eye.
46. Sphenoid Bone
Between the body and lesser wing, just anterior to the
sella turcica is the optic foramen.
Lateral to the body between the greater and lesser
wings is a triangular slit called the superior orbital
fissure.
Pterygoid process – structures project inferiorly from
the point where the body and wings unite and form the
lateral posterior region of the nasal cavity.
Some of the muscles that move the mandible attach to
the pterygoid process.
47. Sphenoid Bone
At the base of the pterygoid process in the
greater wings is the foramen ovale.
The foramen lacerum is bounded
anteriorly by the sphenoid bone and
medially by sphenoid and occipital bones
Foramen rotundum – located at the
junction of the anterior and medial parts of
the sphenoid bone.
48.
49. Ethmoid Bone
Light, spongylike bone, located on the
midline in the anterior part of the cranial
floor medial to the orbits.
Anterior to the sphenoid and posterior to
the nasal bones
51. Ethmoid Bone
Ethmoid bone forms:
Part of the anterior portion of the cranial
floor
Medial wall of the orbit
Superior portion of the nasal septum
Most of the superior sidewalls of the
nasal cavity.
52. Ethmoid Bone
The lateral masses of the ethmoid bone
compose most of the wall between the
nasal cavity and orbits.
Contain 3 to 18 air spaces, or “cells”.
The ethmoidal cells together to form
ethmoidal sinuses.
The perpendicular plate forms the
superior portion of the nasal septum
53.
54.
55. Ethmoid Bone
The cribriform plate lies in the anterior floor of
the cranium and forms the roof of the nasal
cavity.
The cribriform plate contain olfactory foramina
through which axons of the olfactory nerve
pass.
Projecting upward from the cribriform plate is
a triangular process called the crista galli.
This structure is serve as a point of
attachment for the membrane that cover the
brain.
58. Ethmoid Bone
The lateral masses of the ethmoid bone
contain 2 thin, scroll shaped projection
lateral to the nasal septum.
These are the superior nasal conchae
and middle nasal conchae.
A third pair of conchae, the inferior nasal
conchae, are separated bones.
59.
60. Ethmoid Bone
The conchae cause turbulance in inhaled air, which
result in many inhaled particles striking and becoming
trapped in the mucus that lines the nasal
passageways.
This turbulence thus cleanses the inhaled air before it
passes into the rest of the respiratory tract.
Turbulence airflow around the superior nasal
conchae also aids in the distribution of olfactory
stimulants for the sensation of smell.
Air striking and mucous lining of the conhae is also
warmed and moisted.
61.
62.
63. Nasal Bones
Paired of the nasal bones meet at the
midline
Form part of the bridge of the nose
The rest of the supporting tissue of the
nose consists of cartilage
64. Maxillae
A paired maxillae unite together to form
the upper jawbone
Articulate with every bone of the face
except the mandible (lower jawbone)
Forms part of the floor of the orbits, part of
the lateral walls and floor of the nasal
cavity, and most of the hard palate.
65. Maxillae
The hard palate is a bony partition formed by
palatine process of the maxillae and horizontal
plates of the palatine bones that forms roof of
the mouth.
Each maxillae contains a large maxillary sinus
that empties into the nasal cavity.
The alveolar process of the maxillae is an
arch that contain the alveoli (sockets) for the
maxillary (upper) teeth.
66. Maxillae
The palatine process is a horizontal projection
of the maxillae that forms the anterior three
quarters of the hard palate.
The union and diffusion of the maxillary bones
normally is completed before birth.
The infraorbital foramen is an opening in the
maxillae below the orbit.
Inferior orbital fissure, located between the
greater wing of the sphenoid and the maxilla.
68. Zygomatic Bones
2 zygomatic bones
Called cheekbones
Form the prominence of the cheek and
part of the lateral wall and floor of each
orbit
Articulate with the maxillae and the
frontal, sphenoid and temporal bones.
69. Lacrimal Bones
In pair
Smallest bones of the face
Thin, resemble a fingernail in size and shape
Posterior and lateral to nasal bones and form
a part of medial wall of each orbit
Contain lacrimal fossa, vertical tunnel formed
with maxilla, that houses for the lacrimal sac.
Lacrimal fossa – gathers tears and passes
them into the nasal cavity.
70. Palatine Bones
In pair
L-shaped
Form the posterior portion of the hard palate,
part of the floor and lateral wall of the nasal
cavity, and smallest portion of the floors of the
orbits.
The horizontal palate of the palatine bones form
the posterior portion of the hard palate, which
separate the nasal cavity and oral cavity
71.
72. Inferior Nasal Conchae
In pair
Inferior to the middle nasal conchae of the
ethmoid bone
Scroll like bones that form a part of the inferior
lateral wall of the nasal cavity and project into
the nasal cavity.
The inferior nasal conchae is a separate
bones, they are not part of the ethmoid bone
73. Inferior Nasal Conchae
All three pairs of the nasal conchae help
swirl and filter air before it passes into the
lungs.
Only superior nasal conchae involve in
the sense of smell
74. Vomer
Triangular bone
Located in the floor of the nasal
cavity
Articulates superiorly with
perpendicular plate of the
ethmoid bone and inferiorly with
both the maxilla and palatine
along the midline
It is a part of the nasal septum,
partition that divides the nasal
cavity into right and left sides.
75. Mandible
Lower jawbone
Largest, strongest facial bone
Movable skull bone
Consist of a curved , horizontal portion, the
body, and two perpendicular portions, the rami.
The angle of the mandible is the area where
each ramus meets the body
76. Mandible
Each ramus has a posterior condylar process.
On each condylar process has a articulating surface
called mandibular condyle that articulates with the
mandibular fossa and articular tubercle of the
temporal bones.
This articulation called temporomandibular joint
(TMJ)
Has anterior coronoid process to which temporalis
muscles attaches.
The depression between coronoid and condylar
process called the mandibular notch
77. Mandible
The alveolar process is an arch containing the alveoli
(sockets) for the mandibular (lower) teeth.
The mental foramen is located below the mandibular second
premolar tooth.
The mandibular foramen on the medial surface of each
ramus.
The mandibular foramen, beginning of the mandibular canal,
which run obliquely in the ramus and anteriorly to the body
deep to the roots of the teeth
78. Mandible
The inferior alveolar nerves and blood
vessels, which are distributed to the
mandibular teeth, pass through this canal.
80. Hyoid Bone
Single
Unique, does not articulate with any bones
Suspended from the styloid processes of the
temporal bones by ligaments and muscles.
Located in the anterior neck between the mandible
and larynx
Support the tongue, providing attachment sites for
some tongue muscles and for muscles of the neck
and pharynx.
81. Hyoid Bone
Consists horizontal body and paired
projection called the lesser horns and the
greater horns.
Muscles and ligaments attach to these
paired projection.
84. The Important of Hyoid Bone
It helps to support the tongue and serves as an attachment
point for several muscles that help to elevate the larynx during
swallowing and speech.
The hyoid bone is unique in that it is the only bone of the body
that does not articulate with any other bone.
Instead, it is suspended above the larynx where it is anchored
by ligaments to the styloid processes of the temporal bones of
the skull.
When depressed it also assists in locating vocal chords when
intubating a patient
85. Sutures
Immovable joint
Holds skull bone
together
5 prominent
suture:
Coronal
Sagittal
Lambdoid
Squamous
metopic
86. Paranasal Sinuses
Cavities within
certain cranial and
facial bones and
connecting with
nasal cavity
Lined with mucous
membrane.
Frontal, sphenoid,
ethmoid and
maxillary sinus.
87. Fontanels
Soft spot – areas of unossified
mesenchyme.
Soon after birth it gradually become
suture (intramembranous ossification)
Anterior fontanel
Posterior fontanel
Anterolateral
Posterolateral
91. FRONTALIS
The frontalis muscle is thin, of a quadrilateral form, and
intimately adherent to the superficial fascia.
It is broader than the occipitalis and its fibers are longer
and paler in color. It is located on the front of the head.
The muscle has no bony attachments. Its medial fibers
are continuous with those of the procerus; its immediate
fibers blend with the corrugator and orbicularis oculi
muscles, thus attached to the skin of the eyebrows; and
its lateral fibers are also blended with the latter muscle
over the zygomatic process of the frontal bone.
92. In the eyebrows, its primary function is to
lift them (thus opposing the orbital portion
of the orbicularis), especially when looking
up. It also acts when a view is too distant
or dim.
93. OCCIPITALIS
The occipitalis muscle is thin and quadrilateral in form. It
arises from tendinous fibers from the lateral two-thirds of
the superior nuchal line of the occipital bone and from
the mastoid process of the temporal and ends in the
galea aponeurotica.
The occipitalis muscle is innervated by the facial nerve
and its function is to move the scalp back. The muscles
receives blood from the occipital artery.
98. Orbicularis oris
Orbicularis oris is recognized that the muscle
actually consists of four substantially independent
quadrants (upper, lower, left and right), each of
which contains a larger pars peripheralis and a
smaller pars marginalis.
Marginal and peripheral parts are apposed
along lines that correspond externally to the lines
of junction between the vermilion zone of the lip
and the skin.
99. Thus, orbicularis oris is composed of eight
segments, each of which is named
systematically according to its location.
Each segment resembles a fan that has
its stem at the modulus and is open in
peripheral segments and almost closed in
marginal segments
100. Vascular supply
Orbicularis oris is supplied mainly by the superior
and inferior labial branches of the facial artery,
the mental and infraorbital branches of the
maxillary artery and the transverse facial branch
of the superficial temporal artery.
Nerve supply
Orbicularis oris is supplied by the buccal and
mandibular branches of the facial nerve.
101. ACTION
Lip protrusion
Kissing muscle cause it is caused to
pucker the lip.
Whistling
Lip pouching
Left and right turning of lip
Up and down movement of lip
102.
103. Levator labii superioris alaequae nasi
Levator labii superioris alaequae nasi arises from the
upper part of the frontal process of the maxilla and,
passing obliquely downwards and laterally, divides into
medial and lateral slips.
The medial slip is inserted into the greater alar cartilage
of the nose and the skin over it. The lateral slip is
prolonged into the lateral part of the upper lip, where it
blends with levator labii superioris and orbicularis oris.
Superficial fibres of the lateral slip curve laterally across
the front of levator labii superioris and attach along the
floor of the dermis at the upper part of the nasolabial
furrow and ridge
104. Vascular supply
Levator labii superioris alaequae nasi is supplied by the
facial artery and the infraorbital branch of the maxillary
artery.
Innervation
Levator labii superioris alaequae nasi is innervated by
zygomatic and buccal branches of the facial nerve.
Actions
The lateral slip raises and everts the upper lip and raises,
deepens and increases the curvature of the top of the
nasolabial furrow. The medial slip dilates the nostril,
displaces the circumalar furrow laterally, and modifies its
curvature
105.
106. Levator labii superioris
Levator labii superioris starts from the infraorbital margin,
where it arises from the maxilla and zygomatic bone
above the infraorbital foramen. Its fibres converge into
the muscular substance of the upper lip between the
lateral slip of levator labii superioris alaequae nasi and
zygomaticus minor.
Vascular supply
Levator labii superioris is supplied by the facial artery and
the infraorbital branch of the maxillary artery.
Innervation
Levator labii superioris is innervated by the zygomatic and
buccal branches of the facial nerve.
107. Actions
Levator labii superioris elevates and everts
the upper lip. Acting with other muscles, it
modifies the nasolabial furrow. In some
faces, this furrow is a highly characteristic
feature and it is often deepened in
expressions of sadness or seriousness
108.
109. Zygomaticus major
Zygomaticus major arises from the zygomatic
bone, just in front of the zygomaticotemporal
suture, and passes to the angle of the mouth
where it blends with the fibres of levator anguli
oris, orbicularis oris and more deeply placed
muscular bands.
Vascular supply
Zygomaticus major is supplied by the superior
labial branch of the facial artery.
110. Innervation
Zygomaticus major is innervated by the zygomatic
and buccal branches of the facial nerve.
Actions
Zygomaticus major draws the angle of the mouth
upwards and laterally as in laughing
111. Zygomaticus minor
Zygomaticus minor arises from the lateral surface
of the zygomatic bone immediately behind the
zygomaticomaxillary suture, and passes
downwards and medially into the muscular
substance of the upper lip. Superiorly it is
separated from levator labii superioris by a narrow
triangular interval, and inferiorly it blends with this
muscle.
Vascular supply
Zygomaticus minor is supplied by the superior
labial branch of the facial artery.
112. Innervation
Zygomaticus minor is innervated by the zygomatic and
buccal branches of the facial nerve.
Actions
Zygomaticus minor elevates the upper lip, exposing the
maxillary teeth. It also assists in deepening and elevating
the nasolabial furrow. Acting together, the main elevators
of the lip - levator labii superioris alaequae nasi, levator
labii superioris and zygomaticus minor - curl the upper lip
in smiling, and in expressing smugness, contempt or
disdain.
113.
114. Levator anguli oris
Levator anguli oris arises from the canine fossa of
the maxilla, just below the infraorbital foramen and
inserts into and below the angle of the mouth. Its
fibres mingle there with other muscle fibres
(zygomaticus major, depressor anguli oris,
orbicularis oris). Some superficial fibres curve
anteriorly and attach to the dermal floor of the
lower part of the nasolabial furrow. The infraorbital
nerve and accompanying vessels enter the face
via the infraorbital foramen between the origins of
levator anguli oris and levator labii superioris.
115. Vascular supply
Levator anguli oris is supplied by the superior labial
branch of the facial artery and the infraorbital branch of
the maxillary artery.
Innervation
Levator anguli oris is innervated by the zygomatic and
buccal branches of the facial nerve.
Actions
Levator anguli oris raises the angle of the mouth in
smiling, and contributes to the depth and contour of the
nasolabial furrow
116. Mentalis
Mentalis is a conical fasciculus lying at the side of the
frenulum of the lower lip. The fibres arise from the
incisive fossa of the mandible and descend to attach to
the skin of the chin.
Vascular supply
Mentalis is supplied by the inferior labial branch of the facial
artery and the mental branch of the maxillary artery.
Innervation
Mentalis is innervated by the mandibular branch of the
facial nerve.
Actions
Mentalis raises the lower lip, wrinkling the skin of the chin.
Since it raises the base of the lower lip, it helps in
protruding and everting the lower lip in drinking and also
in expressing doubt or disdain.
117. Depressor labii inferioris
Depressor labii inferioris is a quadrilateral muscle
that arises from the oblique line of the mandible,
between the symphysis menti and the mental
foramen. It passes upwards and medially into the
skin and mucosa of the lower lip, blending with the
paired muscle from the opposite side and with
orbicularis oris. Below and laterally it is continuous
with platysma.
Vascular supply
Depressor labii inferioris is supplied by the inferior
labial branch of the facial artery and the mental
branch of the maxillary artery.
118. Innervation
Depressor labii inferioris is innervated by the
mandibular branch of the facial nerve.
Actions
Depressor labii inferioris draws the lower lip
downwards and a little laterally in
masticatory activity, and may assist in
eversion of the lower lip. It contributes to
the expressions of irony, sorrow,
melancholy and doubt
119. Depressor anguli oris
Depressor anguli oris has a long, linear origin from
the mental tubercle of the mandible and its
continuation, the oblique line, below and lateral to
depressor labii inferioris. It converges into a
narrow fasciculus that blends at the angle of the
mouth with orbicularis oris and risorius. Some
fibres continue into the levator anguli oris muscle.
Depressor anguli oris is continuous below with
platysma and cervical fasciae. Some of its fibres
may pass below the mental tubercle and cross the
midline to interlace with their contralateral fellows;
these constitute the transversus menti (the 'mental
sling').
120. Vascular supply
Depressor anguli oris is supplied by the inferior labial
branch of the facial artery and the mental branch of the
maxillary artery.
Innervation
Depressor anguli oris is innervated by the buccal and
mandibular branches of the facial nerve.
Actions
Depressor anguli oris draws the angle of the mouth
downwards and laterally in opening the mouth and in
expressing sadness. During opening of the mouth the
mentolabial sulcus becomes more horizontal and its
central part deeper.
121. Buccinator
The muscle of the cheek, buccinator, is a thin
quadrilateral muscle which occupies the interval between
the maxilla and the mandible. Its upper and lower
boundaries are attached respectively to the outer
surfaces of the alveolar processes of the maxilla and
mandible opposite the molar teeth. Its posterior border is
attached to the anterior margin of the pterygomandibular
raphe. In addition, a few fibres spring from a fine
tendinous band that bridges the interval between the
maxilla and the pterygoid hamulus, between the
tuberosity of the maxilla and the upper end of the
pterygomandibular raphe. On its way to the soft palate
the tendon of tensor veli palatini pierces the pharyngeal
wall in the small gap that lies behind this tendinous band
122. The posterior part of buccinator is deeply placed, internal
to the mandibular ramus and in the plane of the medial
pterygoid plate. Its anterior component curves out behind
the third molar tooth to lie in the submucosa of the cheek
and lips. The fibres of buccinator converge towards the
modiolus near the angle of the mouth. Here the central
(pterygomandibular) fibres intersect, those from below
crossing to the upper part of orbicularis oris, and those
from above crossing to the lower part. The highest
(maxillary) and lowest (mandibular) fibres of buccinator
continue forward to enter their corresponding lips without
decussation. As buccinator courses through the cheek
and modiolus substantial numbers of its fibres are
diverted internally to attach to submucosa.
123. Vascular supply
Buccinator is supplied by branches from the facial artery and the
buccal branch of the maxillary artery.
Innervation
Buccinator is supplied by the buccal branch of the facial nerve
Actions
Buccinator compresses the cheek against the teeth and gums during
mastication, and assists the tongue in directing food between the
teeth. As the mouth closes, the teeth glide over the buccolabial
mucosa, which must be retracted progressively from their occlusal
surfaces by buccinator and other submucosally attached muscles.
When the cheeks have been distended with air, the buccinators
expel it between the lips, an activity important when playing wind
instruments, accounting for the name of the muscle (Latin
buccinator = trumpeter).
124. Risorius
Risorius is a highly variable muscle that ranges from one or more
slender fascicles to a wide, thin superficial fan. Its peripheral
attachments may include some or all of the following: the zygomatic
arch, parotid fascia, fascia over the masseter anterior to the parotid,
fascia enclosing pars modiolaris of platysma, and fascia over the
mastoid process. Its fibres converge to apical and subapical
attachments at the modiolus.
Vascular supply
Risorius is supplied mainly by the superior labial branch of the facial
artery.
Nerve supply
Risorius is supplied by buccal branches of the facial nerve.
Actions
Risorius pulls the corner of the mouth laterally in numerous facial
activities, including grinning and laughing.
132. MASSETER
Consists of three layers which blend anteriorly.
The superficial layer is the largest.
It arises by a thick aponeurosis from the
maxillary process of the zygomatic bone and
from the anterior two-thirds of the inferior border
of the zygomatic arch.
Its fibres pass downwards and backwards, to
insert into the angle and lower posterior half of
the lateral surface of the mandibular ramus.
133. The middle layer of masseter arises from the
medial aspect of the anterior two-thirds of the
zygomatic arch and from the lower border of the
posterior third of this arch.
It inserts into the central part of the ramus of the
mandible.
The deep layer arises from the deep surface of
the zygomatic arch and inserts into the upper
part of the mandibular ramus and into its
coronoid process.
134. Skin, platysma, risorius, zygomaticus major, the parotid
gland and duct, branches of the facial nerve and the
transverse facial branches of the superficial temporal
vessels are all superficial relations. Temporalis and the
ramus of the mandible lie deep to masseter. The anterior
margin of masseter is separated from buccinator and the
buccal branch of the mandibular nerve by a buccal pad
of fat and crossed by the facial vein. The posterior
margin of the muscle is overlapped by the parotid gland.
The masseteric nerve and artery reach the deep surface
of masseter by passing over the mandibular incisure
(mandibular notch).
135. Vascular supply
Masseter is supplied by the masseteric
branch of the maxillary artery, the facial
artery and the transverse facial branch of
the superficial temporal artery.
136. Innervation
Masseter is supplied by the masseteric
branch of the anterior trunk of the
mandibular nerve.
137. Actions
Masseter elevates the mandible to
occlude the teeth in mastication and has a
small effect in side-to-side movements,
protraction and retraction. Its electrical
activity in the resting position of the
mandible is minimal
138. Submasseteric space infections
Sometimes infection around a mandibular
third molar tooth tracks backwards, lateral
to the mandibular ramus and pus localizes
deep to the attachment of masseter in the
submasseteric tissue space. Such an
abscess, lying deep to this thick muscle
produces little visible swelling, but is
accompanied by profound muscle spasm
and limitation of jaw opening.
140. Temporalis arises from the whole of the
temporal fossa up to the inferior temporal line -
except the part formed by the zygomatic bone -
and from the deep surface of the temporal
fascia.
Its fibres converge and descend into a tendon
which passes through the gap between the
zygomatic arch and the side of the skull.
141. The muscle is attached to the medial surface,
apex, anterior and posterior borders of the
coronoid process and to the anterior border of
the mandibular ramus almost up to the third
molar tooth. The anterior fibres of temporalis are
orientated vertically, the most posterior fibres
almost horizontally, and the intervening fibres
with intermediate degrees of obliquity, in the
manner of a fan. Fibres of temporalis may
occasionally gain attachment to the articular disc
142. Skin, auriculares anterior and superior, temporal
fascia, superficial temporal vessels, the
auriculotemporal nerve, temporal branches of
the facial nerve, the zygomaticotemporal nerve,
the epicranial aponeurosis, the zygomatic arch
and the masseter muscle are all superficial
relations.
Posterior relations of temporalis are the
temporal fossa above and the major
components of the infratemporal fossa below.
Behind the tendon of the muscle, the masseteric
nerve and vessels traverse the mandibular
notch. The anterior border is separated from the
zygomatic bone by a mass of fat.
143. VASCULAR SUPPLY
Temporalis is supplied by the deep
temporal branches from the second part of
the maxillary artery. The anterior deep
temporal artery supplies c.20% of the
muscle anteriorly, the posterior deep
temporal supplies c.40% of the muscle in
the posterior region and the middle
temporal artery supplies c.40% of the
muscle in its mid-region.
144. Innervation
Temporalis is supplied by the deep
temporal branches of the anterior trunk of
the mandibular nerve.
145. ACTION
Temporalis elevates the mandible and so closes
the mouth and approximates the teeth. This
movement requires both the upward pull of the
anterior fibres and the backward pull of the
posterior fibres, because the head of the
mandibular condyle rests on the articular
eminence when the mouth is open. The muscle
also contributes to side-to-side grinding
movements. The posterior fibres retract the
mandible after it has been protruded.
146. Lateral pterygoid
Lateral pterygoid is a short, thick muscle
consisting of two parts. The upper head arises
from the infratemporal surface and infratemporal
crest of the greater wing of the sphenoid bone.
The lower head arises from the lateral surface of
the lateral pterygoid plate. From the two origins,
the fibres converge, and pass backwards and
laterally, to be inserted into a depression on the
front of the neck of the mandible (the pterygoid
fovea).
147.
148. Relations
The superficial head of medial pterygoid and the
tendon of temporalis, are all superficial relations.
Deep to the muscle are the deep head of medial
pterygoid, the sphenomandibular ligament, the
middle meningeal artery, and the mandibular
nerve.
The upper border is related to the temporal and
masseteric branches of the mandibular nerve
and the lower border is related to the lingual and
inferior alveolar nerves. The buccal nerve and
the maxillary artery pass between the two heads
of the muscles
149. Vascular supply
Lateral pterygoid is supplied by pterygoid
branches from the maxillary artery which
are given off as the artery crosses the
muscle and from the ascending palatine
branch of the facial artery.
150. Innervation
The nerves to lateral pterygoid (one for
each head) arise from the anterior trunk of
the mandibular nerve, deep to the muscle.
The upper head and the lateral part of the
lower head receive their innervation from a
branch given off from the buccal nerve.
However, the medial part of the lower
head has a branch arising directly from
the anterior trunk of the mandibular nerve
151. Actions
When left and right muscles contract together the condyle is pulled
forward and slightly downward. This protrusive movement alone has
little or no function except to assist opening the jaw.
Digastric and geniohyoid are the main jaw opening muscles: unlike
lateral pterygoid, when acting alone they rotate the jaw open,
provided other muscles attached to the hyoid prevent if from being
pulled forward.
If only one lateral pterygoid contracts, the jaw rotates about a
vertical axis passing roughly through the opposite condyle and is
pulled medially toward the opposite side. This contraction together
with that of the adjacent medial pterygoid (both attached to the
lateral pterygoid plate) provides most of the strong medially directed
component of the force used when grinding food between teeth of
the same side. It is arguably the most important function of the
inferior head of lateral pterygoid. It is often stated that the upper
head is used to pull the articular disc forward when the jaw is
opened.
152. Medial pterygoid
Medial pterygoid is a thick, quadrilateral muscle with
two heads of origin.
The major component is the deep head which arises
from the medial surface of the lateral pterygoid plate
of the sphenoid bone and is therefore deep to the
lower head of lateral pterygoid.
The small, superficial head arises from the
maxillary tuberosity and the pyramidal process of
the palatine bone, and therefore lies on the lower
head of lateral pterygoid.
153. The fibres of medial pterygoid descend
posterolaterally and are attached by a
strong tendinous lamina to the
posteroinferior part of the medial surface
of the ramus and angle of the mandible,
as high as the mandibular foramen and
almost as far forwards as the mylohyoid
groove. This area of attachment is often
ridged
154. Relations
The lateral surface of medial pterygoid is related
to the mandibular ramus, from which it is
separated above its insertion by lateral
pterygoid, the sphenomandibular ligament, the
maxillary artery, the inferior alveolar vessels and
nerve, the lingual nerve and a process of the
parotid gland.
The medial surface is related to tensor veli
palatini and is separated from the superior
pharyngeal constrictor by styloglossus and
stylopharyngeus and by some areolar tissue.
155. Vascular supply
Medial pterygoid derives its main arterial
supply from the pterygoid branches of the
maxillary artery.
157. Actions
The medial pterygoid muscles assist in
elevating the mandible. Acting with the lateral
pterygoids they protrude it. When the medial
and lateral pterygoids of one side act
together, the corresponding side of the
mandible is rotated forwards and to the
opposite side, with the opposite mandibular
head as a vertical axis. Alternating activity in
the left and right sets of muscles produces
side-to-side movements, which are used to
triturate food.
158. Muscles Move The Tongue
Genioglossus
Styloglossus
Platoglossus
hyoglossus
159.
160. Genioglossus
Genioglossus is triangular in sagittal section,
lying near and parallel to the midline. It arises
from a short tendon attached to the superior
genial tubercle behind the mandibular
symphysis, above the origin of geniohyoid. From
this point it fans out backwards and upwards.
The inferior fibres of genioglossus are attached
by a thin aponeurosis to the upper anterior
surface of the hyoid body near the midline (a few
fasciculi passing between hyoglossus and
chondroglossus to blend with the middle
constrictor of the pharynx).
161. Vascular supply
Genioglossus is supplied by the sublingual branch of
the lingual artery and the submental branch of the
facial artery.
Innervation
Genioglossus is innervated by the hypoglossal nerve.
Actions
Genioglossus brings about the forward traction of the
tongue to protrude its apex from the mouth. Acting
bilaterally, the two muscles depress the central part
of the tongue, making it concave from side to side.
Acting unilaterally, the tongue diverges to the
opposite side
162. Hyoglossus
Hyoglossus is thin and quadrilateral, and
arises from the whole length of the greater
cornu and the front of the body of the
hyoid bone. It passes vertically up to enter
the side of the tongue between
styloglossus laterally and the inferior
longitudinal muscle medially. Fibres
arising from the body of the hyoid overlap
those from the greater cornu.
163. Vascular supply
Hyoglossus is supplied by the sublingual
branch of the lingual artery and the
submental branch of the facial artery.
Innervation
Hyoglossus is innervated by the hypoglossal
nerve.
Action
Hyoglossus depresses the tongue.
164. Styloglossus
Styloglossus is the shortest and smallest of the
three styloid muscles. It arises from the
anterolateral aspect of the styloid process near
its apex, and from the styloid end of the
stylomandibular ligament. Passing downwards
and forwards, it divides at the side of the tongue
into a longitudinal part, which enters the tongue
dorsolaterally to blend with the inferior
longitudinal muscle in front of hyoglossus, and
an oblique part, overlapping hyoglossus and
decussating with it.
165. Vascular supply
Styloglossus is supplied by the sublingual
branch of the lingual artery.
Innervation
Styloglossus is innervated by the
hypoglossal nerve.
Action
Styloglossus draws the tongue up and
backwards
166.
167. Muscles of the Anterior Neck
Located superior to the hyoid bone
(suprahyoid muscles)
1. Digastric
2. Stylohyoid
3. Mylohyoid
4. geniohyoid
168. DIGASTRIC
Digastric has two bellies and lies below the mandible,
extending from the mastoid process to the chin . The
posterior belly, which is longer than the anterior, is
attached in the mastoid notch of the temporal bone, and
passes downwards and forwards. The anterior belly is
attached to the digastric fossa on the base of the
mandible near the midline, and slopes downwards and
backwards. The two bellies meet in an intermediate
tendon which runs in a fibrous sling attached to the body
and greater cornu of the hyoid bone and is sometimes
lined by a synovial sheath. The tendon perforates
stylohyoid.
169. Vascular supply
The posterior belly is supplied by the
posterior auricular and occipital arteries.
The anterior belly of digastric receives its
blood supply chiefly from the submental
branch of the facial artery.
170. Innervation
The anterior belly of digastric is supplied by the mylohyoid
branch of the inferior alveolar nerve, and the posterior
belly is supplied by the facial nerve. The different
innervation of the two parts reflects their separate
derivations from the mesenchyme of the first and second
branchial arches.
Actions
Digastric depresses the mandible and can elevate the
hyoid bone. The posterior bellies are especially active
during swallowing and chewing.
171. STYLOHYOID
Stylohyoid arises by a small tendon from the
posterior surface of the styloid process, near its
base. Passing downwards and forwards, it
inserts into the body of the hyoid bone at its
junction with the greater cornu (and just above
the attachment of the superior belly of
omohyoid) It is perforated near its insertion by
the intermediate tendon of digastric. The muscle
may be absent or double. It may lie medial to the
external carotid artery and may end in the
suprahyoid or infrahyoid muscles.
172. Vascular supply
Stylohyoid receives its blood supply from branches of the
facial, posterior auricular and occipital arteries.
Innervation
Stylohyoid is innervated by the stylohyoid branch of the
facial nerve, which frequently arises with the digastric
branch, and enters the middle part of the muscle.
Actions
Stylohyoid elevates the hyoid bone and draws it
backwards, elongating the floor of the mouth.
173. Muscles of the Anterior Neck
Located superior to the hyoid bone
(Infrahyoid muscles)
1. Omohyoid
2. Sternohyoid
3. Sternothyroid
4. Thyrohyoid
174. STERNOHYOID
Sternohyoid is a thin, narrow strap muscle that arises
from the posterior surface of the medial end of the
clavicle, the posterior sternoclavicular ligament and the
upper posterior aspect of the manubrium sterni. It
ascends medially and is attached to the inferior border of
the body of the hyoid bone. Inferiorly, there is a
considerable gap between the muscle and its
contralateral fellow, but the two usually come together in
the middle of their course, and are contiguous above
this. Sternohyoid may be absent or double, augmented
by a clavicular slip (cleidohyoid), or interrupted by a
tendinous intersection.
175. Vascular supply
Sternohyoid is supplied by branches from
the superior thyroid artery.
Innervation
Sternohyoid is innervated by branches from
the ansa cervicalis (C1, 2, 3).
Action
Sternohyoid depresses the hyoid bone after
it has been elevated.
176. OMOHYOID
Omohyoid consists of two bellies.
The inferior belly is a flat, narrow band,
which inclines forwards and slightly
upwards across the lower part of the neck.
It arises from the upper border of the
scapula, near the scapular notch, and
occasionally from the superior transverse
scapular ligament. It then passes behind
sternocleidomastoid and ends there in the
intermediate tendon.
177. The superior belly begins at the
intermediate tendon, passes almost
vertically upwards near the lateral border
of sternohyoid and is attached to the lower
border of the body of the hyoid bone
lateral to the insertion of sternohyoid.
178. Vascular supply
Omohyoid is supplied by branches from the superior
thyroid and lingual arteries.
Innervation
The superior belly of omohyoid is innervated by branches
from the superior ramus of the ansa cervicalis (C1). The
inferior belly is innervated from the ansa cervicalis itself
(C1, 2 and 3).
Actions
Omohyoid depresses the hyoid bone after it has been
elevated. It has been speculated that the muscle tenses
the lower part of the deep cervical fascia in prolonged
inspiratory efforts, reducing the tendency for soft parts to
be sucked inward.
179. STERNOTHYROID
Sternothyroid is shorter and wider than
sternohyoid, and lies deep and partly medial to
it. It arises from the posterior surface of the
manubrium sterni inferior to the origin of
sternohyoid and from the posterior edge of the
cartilage of the first rib. It is attached above to
the oblique line on the lamina of the thyroid
cartilage, where it delineates the upward extent
of the thyroid gland. In the lower part of the neck
the muscle is in contact with its contralateral
fellow, but the two diverge as they ascend
180. Vascular supply
Sternothyroid is supplied by branches from the
superior thyroid and lingual arteries.
Innervation
Sternothyroid is innervated by branches from the
ansa cervicalis (C1, 2 and 3).
Action
Sternothyroid draws the larynx downwards after it
has been elevated by swallowing or vocal
movements. In the singing of low notes, this
downward traction would be exerted with the
hyoid bone relatively fixed.
181. THYROHYOID
Thyrohyoid is a small, quadrilateral muscle
that may be regarded as an upward
continuation of sternothyroid (Fig. 31.5). It
arises from the oblique line on the lamina of
the thyroid cartilage, and passes upwards to
attach to the lower border of the greater
cornu and adjacent part of the body of the
hyoid bone.
182. Vascular supply
Thyrohyoid is supplied by branches from the superior
thyroid and lingual arteries.
Innervation
Unlike the other infrahyoid muscles, thyrohyoid is not
innervated by the ansa cervicalis. In common with
geniohyoid, it is supplied by fibres from the first cervical
spinal nerve which branch off from the hypoglossal nerve
beyond the descendens hypoglossi.
Actions
Thyrohyoid depresses the hyoid bone. With the hyoid bone
stabilized, it pulls the larynx upwards, e.g. when high
notes are sung.
