The A to Z of Skull Bones

The
A to Z
of
Bones of The Skull

Dr A. L. Neill
BSc MSc MBBS PhD FACBS
medicalamanda@gmail.com

The
A to Z

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of
Bones of The Skull
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The A to Z of the Bones of the Skull

Introduction
After the A to Z of Skeletal Muscles was released to my

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students (and later my colleagues with the help of Aspen),
I received some very valuable feedback from both. From this
feedback it became apparent that this format was helpful to all
in the health professional field. It was also apparent that there
was a need for another pocket reference
book of this type on bones and

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nerves. So as with the other book,
I have started with a prototype
examining the bones of one of the
most complex group in the body,
the SKULL.
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It is hoped that this proves to be as
useful as my first A to Z book, and
goes on to become a more
comprehensive but quick and simple reference
for all bones.
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Acknowledgement
I would like to thank Aspen Pharmacare Australia and
particularly Mr Greg Lam CEO and Mr Robert Koster Head of
Marketing and Sales for stepping in and giving me their
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support in this project when it seemed I was not going to be
able to complete it, due to lack of resources and time.
Students, as always, but particularly today have to sacrifice
many things in their pursuit of knowledge. It is hoped that this
book will help to make that pathway easier and more
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enjoyable. As with my other ventures in this A to Z series we
want to give knowledge to any who wish to use it.

Dedication
To MICKEY 390335, and to stopping pettiness, spite and
misinformation wherever it lies.
1 © A. L. Neill


How to use this book
After examining the SKULL as a WHOLE from many view

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points, identifying individual bones, cavities, impressions and
surfaces and including common radiological views, with
explanatory diagrams, this book lists all the bones of the skull
in ALPHABETICAL order as far as possible. Images of the Skull
“in situ” are also included.

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Features are named using in the most familiar terms and those
agreed upon by anatomical nomenclature convention avoiding
eponymous terms wherever possible but as with all anatomical
studies sometimes several terms are used to name the same
feature. Wherever this is common and to save confusion
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reference is made to each term. Similarly between disciplines
such as radiology and osteology as well as anatomy the same
view may be described several different ways,
so when this is also common and to
provide clarity these terms are mentioned.
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The pages facing each image contain the
key/legends to the labels on that diagram.
This is to help in the learning of the features
and to prevent confusion in the examination of
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the bones. Numbering commences anew with each diagram.
However, with some bones one view is not enough (e.g.
Temporal and Sphenoid) to conceptualize all the surfaces and
articulations, so these bones are then shown with the same
numbering sequentially in an alphabetical way, on each related
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diagram. Occasionally they are also shown “in situ”, in other
words as they lay in the skull. This is particularly the case with
the Palatine bones. These bones are hard to see as they are
surrounded by other structures and deeply embedded in the
head, so several views and rotations of the bone are shown
and labelled to see their connections, as well as a view
showing how they are placed relative to other bones.

© A. L. Neill 2


Capitalization is used to demonstrate the bones involved in

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several structures including joints of all kinds (e.g. sutures).
In other words the parietomastoid suture is listed as Parieto-
Mastoid suture to further remind the reader of the involved
bones or bony features involved in the composition of the
structure. This helps to further orientate the reader to the
structural components of the feature.

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It is hoped that this will prove a valuable resource for those
examining individual bones as in the study of ANATOMY and its
many uses such as: archeology, anthropology, chiropractic
dentistry, forensics, geology, medicine, orthopaedics, osteology,
nd
paleontology, paleobiology, physiotherapy and surgery. It is to
be a forerunner of a more complete listing of all bones from A
to Z and a more extensive development of other aspects of the
skull such as measurement markers, development milestones,
individual and ethnic variations -
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“the A to Z of the Skull part
II”. Hence any
suggestions on format
or inclusions will be
gratefully received.
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Thank you

Amanda Neill
BSc MSc MBBS PhD FACBS
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ISBN 1 74138 166 5

3 © A. L. Neill

© A. L. Neill
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Red spots indicate when there is an articulation or joint between the bones. Please note the hyoid does not articulate with any bones and the mandible
articulates at the only synovial joint in the skull- the TMJ -temporomandibular joint. All other joints are secondary cartilagenous bone-fibrocartilage-bone.


Table of contents
Introduction 1

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Acknowledgement 1
Dedication 1
How to Use this book 2
Table of Articulations of the Skull 4
Common Terms used in Osteology 7
Classification and summary of skull bones 12

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The Skull 13-36
External Skull Anterior (norma frontalis)
radiology - occipitofrontal (complete)
radiology - occipitofrontal (upper aspect)
radiology - occipitomental (lower aspect)
External Skull Inferior (Base of Skull) (norma basilaris)
nd
radiology - submentovertical view (view from below)
External Skull Lateral (norma lateralis)
radiology - lateral
External Skull Posterior (norma occipitalis)
External Skull Superior (norma verticularis)
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Internal Skull Inferior - Skull Cap
Internal Skull Superior - Internal Base - cranial fossae

Bones of the Skull 37-70
Auditory Ossicles: malleus, incus and stapes enclosed within the
Temporal bone
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Ethmoid bones Anterior & Lateral, Superior, Medial
Frontal bone
Hyoid bone
Lacrimal bones
Mandible
radiology - Orthopantomogram = OPG (Anterior)
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radiology - Lateral (with soft tissue)
radiology mandibular joint (jaw) open and closed see also TMJ
(temporomandibular joint)
Maxilla / Maxillae bones
Maxillae bones Inferior

5 © A. L. Neill


Nasal bones
Occipital External, Internal
Palatine bones
Parietal External, Internal

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Sphenoid Anterior, Posterior
Sutural / Extrasutural bones - Incus
Temporal External, Inferior, Interior
Vomer
Zygoma

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Cavities of the Skull 71-90
Anterior Cranial Fossa
Base of the Skull internal
Cranial Fossae Anterior, Middle, Posterior
Maxillary Sinus
Middle Cranial Fossa
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Nasal cavity Dissected, Lateral, Septum
Orbital cavity (Orbital fossa) Anterior
radiology obital cavity anterior
radiology orbital cavity lateral
Posterior Cranial Fossa
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© A. L. Neill 6


Common terms in Osteology
(the study of bones) (with particular reference to the skull)
Ala A wing, hence a wing-like process as in the Ethmoid bone pl.- alae.

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Alveolus Air filled bone - tooth socket
Aperture An opening or space between bones or within a bone.
Areola Small, open spaces as in the areolar part of the Maxilla.
Articulation Joint, which is a point of contact b/n 2 opposing bones.
Auditory

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Pertaining to hearing, hence, pertaining to the ear.
Axial Refers to the head and trunk (vertebrae, ribs and sternum) of the body.
Basilar Relating to the base or bottom of structures
Basiocranium Bones of the base of the skull
Boss A smooth round broad eminence - mainly in the Frontal bone
female > male
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Bregma Refers to a junction of more than 2 bones in a joint as in the Bregma
of the skull, junction between the coronal and sagittal sutures which in
the infant is not closed and can be felt pulsating - site of the anterior
fontanelle.
Calotte The calotte consists of the calvaria from which the base has been
removed.
Calvaria The calvaria refers to the cranium without the facial bones attached.
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Canal Tunnel / extended foramen as in the carotid canal at the base of the
skull adj,- canular (canicular - small canal)
Caput / Kaput The head or of a head, adj.- capitate = having a head
(c.f.decapitate)
Carotid To put to sleep; compression of the common or internal carotid artery
causes coma. This refers to bony points related to the Carotid vessels
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Cavity An open area or sinus within a bone or formed by two or more bones
(adj. cavernous), may be used interchangeably with fossa. Cavity
tends to be more enclosed fossa a shallower bowl like space (Orbital
fossa-Orbital cavity).
Cavum A cave.
Cephalic Pertaining to the head
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Clinoid Like a bed-post, part of a four poster bed so that clinoid process looks
like a bed post (generally with other posts) as in the Sphenoid bone.
Clivus A slope hence in the anterior cranial fossa referring to a slope on
the base of the cavity.
Cochlea A snail hence snail-like shape relating to the Organ of Corti in the ear.
Concha A shell shaped bone as in the ear or nose (pl. conchae adj.
chonchoid) old term for this turbinate.
Condyle A rounded enlargement or process possessing an articulating surface.

7 © A. L. Neill


Cornu A horn (as in the Hyoid)
Corona A crown. adj.- coronary, coronoid or coronal; hence a coronal plane
is parallel to the main arch of a crown which passes from ear to ear
(c.f. coronal suture).

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Cranium The cranium of the skull comprises all of the bones of the skull except
for the mandible.
Crest Prominent sharp thin ridge of bone formed by the attachment of
muscles particularly powerful ones eg Temporalis/Sagittal crest
Cribiform / EthmoidA sieve or bone with small sieve-like holes.
Cuneate / Cuneus A wedge / wedge-shaped

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Dens A tooth hence dentine and dental relating to teeth, denticulate having
tooth-like projections adj dentate See odontoid
Depression A concavity on a surface
Diaphysis The body of a long bone. In the young this is the region between the
growth plates.
Diploë The cancellous bone between the inner and outer tables of the skull,
adj.- diploic.
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Eminence A smooth projection on a bone.
Endocranium Refers to the interior of the “braincase” adj.- endocranial divided into
the 3 major fossae anterior (for the Frontal lobes) middle (containing
Temporal lobes) and posterior (for the containment of the Cerebellum).
Epiphysis The end of a long bone beyond the growth plate or epiphyseal plate.
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There are 2 epiphyses to each long bone.
Euryon The ectocranial point of the greatest breadth
i.e. the widest point across the skull.
Facet A face, a small bony surface (occlusal facet on the chewing surfaces
of the teeth) seen in planar joints.
Fissure A narrow slit or gap from cleft.
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Fontanelle A fountain, associated with the palpable pulsation of the brain as in
the anterior fontanelle of an infant. These soft spots on the skull are
cartilagenous connective tissue coverings “joints” which allow for skull
cranial expansion and then become the mould for the bone
development and shape joining long the sutural lines, later becoming
the Bregma.
Foramen A natural hole in a bone usually for the transmission of blood vessels
and/or nerves.(pl. foramina).
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Fornix An arch
Fossa A pit, depression, or concavity, on a bone, or formed from several
bones as in temporomandibular fossa. Shallower and more like a
“bowl” than a cavity

Fovea A small pit (usually smaller than a fossa)- as in the fovea of the
occlusal surface of the molar tooth.
Gallus / Galli A cock, hence, crista galli, the cock's comb (i e possessive
form of gallus).

© A. L. Neill 8


Glabella Most anterior midline point of the Frontal bone - that point between
the eyebrows which should be hairless. This is the Latin derivation of
this word.
Gnathion Midline point which is the most inferior point of the Mandible.

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Groove long pit or furrow
Gyrus A circle, hence a coil of brain cortex.
Hamus A hook hence the term used for bones which “hook around other
bones or where other structures are able to attach by hooking -
hamulus = a small hook.
Hyoid U-shaped

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Incisura A notch.
Inter between
Intra within
Introitus An orifice or point of entry to a cavity or space.
Jugum A bridge between 2 halves of a bone pl.( juga) as in Sphenoid .
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Lacerum Something lacerated, mangled or torn eg foramen lacerum small
sharp hole at the base of the skull often ripping tissue in trauma.
Lacrimal Related to tears and tear drops. (noun lacrima)
Lambda From the Greek letter a capital 'L' and written as an inverted V.
(adj.- lambdoid) and used to name the point of connection
between the 3 skull bones Occipital and Temporals.
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Lamina A plate as in the lamina of the vertebra a plate of bone connecting the
vertical and transverse spines (pl. laminae)
Linea A line as in the Nuchal lines of the Occitipum
Locus A place (c.f. location, locate, dislocate).
Magnum Large pl magna
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Malleus Hammer (as in the ear ossicle)
Mandible From the verb to chew, hence, the movable lower jaw;
adj.- mandibular.
Mastoid A breast or teat shape - mastoid process of the Temporal bone.
Maxilla The jaw-bone; now used only for the upper jaw; adj.- maxillary.
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Meatus A short passage; adj.- meatal as in external acoustic meatus
connecting the outer ear with the middle ear.
Mental Relating to the chin (mentum = chin not mens = mind).
Metaphysis The slightly expanded end of the shaft of a bone.
Nasion Midline point where the Nasal and Frontal bones meet .
Neurocranium The neurocranium refers only to the braincase of the skull.
Notch An indentation in the margin of a structure.

9 © A. L. Neill


Nucha The nape or back of the neck adj.- nuchal.
Occiput The prominent convexity of the back of the head Occipitum =
Occipital bone adj.- occipital

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Occulus An eye
Odontoid relating to teeth, toothlike see Dens
Opisthion Midline point at the posterior margin of the Foramen Magnum
Orbit A circle; the name given to the bony socket in which the eyeball
rotates; adj - orbital.
Orifice An opening.

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Os A bone adj osseus
Ossicle A small bone as in the ear ossicles: stapes (stirrup), incus (anvil) and
malleus (hammer).
Ostium A door, an opening, an orifice.
Otic Pertaining to the ear
Ovale Oval shaped
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BONES OF THE SKULL
Palate A roof adj.- palatal or platatine.
Parietal Pertaining to the outer wall of a cavity from paries, a wall.
Parotid Pertaining to a region beside or near the ear
Pars A part of
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Pecten A comb.
Petrous Pertaining to a rock / rocky / stoney adj.- petrosal
Process A general term describing any marked projection or prominence as in
the mandibular process.
Prominens A projection
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Prosthion Midline point of the maxilla alveolar bone which is most anterior
Pterion A wing; the region where the tip of the greater wing of the sphenoid
meets or is close to the parietal, separating the frontal from the
squamous region of the temporal bone. (TERY- on) Alternatively the
region where these 4 bones meet.
Pterygoid Wing shaped
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Recess A secluded area or pocket; a small cavity set apart from a main cavity.
Rectus straight - erect
Rhinion Midline point of the free end of the Nasal bones where they join with
the Nasal cartilages
Ridge elevated bony growth often roughened.
Rotundum Round
Sagittal An arrow, the sagittal suture is notched posteriorly, making it look like
an arrow by the lambdoid sutures.

© A. L. Neill 10


Sella A saddle; adj.- sellar, sella turcica = Turkish saddle.
Sesamoid grainlike

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Sigmoid S-shaped, from the letter Sigma which is S in Greek.
Sinus A space usually within a bone lined with mucous membrane, such as
the frontal and maxillary sinuses in the head, (also, a modified BV
usually vein with an enlarged lumen for blood storage and containing
no or little muscle in its wall). Sinuses may contain air, venous or
arterial blood, lymph or serous fluid depending upon location and
health of the subject adj.- sinusoid.
Skull The skull refers to all of the bones that comprise the head.

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Spheno A wedge i.e. the Sphenoid is the bone which wedges in the base of
the skull between the unpaired frontal and occipital bones
adj.- sphenoid .
Spine A thorn adj.- spinous descriptive of a sharp, slender
process/protrusion.
Splanchocranium The splanchocranium refers to the facial bones of the skull.
Sulcus long wide groove often due to a BV indentation
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Suture The saw-like edge of a cranial bone that serves as joint between
bones of the skull.
Stylos An instrument for writing hence adj.- styloid a pencil-like structure.
Symphysis A joint or a growth
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Tectum A roof.
Tegmen A covering.
Temporal Refers to time and the fact that grey hair (marking the passage of
time) often appears first at the site of the temporal bone.
Tentorium A tent.
Trabecula A “little” beam i.e. supporting structure or strut pl. trabeculae
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Tubercle A small process or bump, an eminence..
Tuberculum A very small prominence, process or bump.
Tuberosity A large rounded process or eminence, a swelling or large rough
prominence often associated with a tendon or ligament attachment.
Turbinate A child’s spinning top, hence shaped like a top. An old term for the
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nasal conchae.
Tympanum A drum pl. tympani
Uncus A hook adj.- uncinate.
Vagina A sheath; hence, invagination is the acquisition of a sheath by
pushing inwards into a structure, and evagination is similar but
produced by pushing outwards adj.- vaginal.
Zygoma A yoke , hence, the bone joining the maxillary, frontal, temporal &
sphenoid bones adj.- zygomatic.

11 © A. L. Neill


Classification and Summary of Skull bones
Flat bones Thin flattened and usually curved bones. Most Skull bones.

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Irregular bones Various shapes not easily classified Sphenoid

Long bone Longer than wide 2 ends epiphysis and a central
diaphysis. Growth mainly lengthwise. Most limb bones.

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Pneumatic bone/Alveolar bone
Bones filled with air to lighten their weight -
Maxilla, Frontal, Mandible and bones with “sinuses”

Sesamoid bone Bones completely surrounded by soft tissue w/o joints
Hyoid
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Short bone Roughly cubic in shape. Most wrist and ankle bones; many
of the bones at the base of the skull.

Sutural bone “Wormian” bone small bones which occur within the skull
sutures sometimes called extra-sutural if the main part of
the bone is outside of the suture. Generally they are
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unnamed although the Incus is the name given to the large
extra-sutural bone when present.

There are: 22 paired skull bones including the ear ossicles / not
including the teeth.
5 single bones mainly on the base of the skull
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1 mandible
1 hyoid
variable sutural and extra-sutural bones (generally between 3-5)
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© A. L. Neill 12


External Skull Anterior

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1 Frontal bone
THE SKULL

2 Fronto-Nasal suture
3 Inter-Nasal suture
4 Nasal bone, Lacrimal bone

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5 Supra-Orbital foramen
6 Spheno-Parietal suture
7 Spheno-Frontal suture
8 Spheno-Squamosal suture
9 Zygoma
10 Zygomatico-Maxillary suture
nd
11 Infra-orbital foramen
12 Middle Nasal concha - turbinate (from Ethmoid bone)
13 Inferior nasal concha - turbinate (from Ethmoid bone)
14 Vomer
15 Mandible
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16 Mental foramen
17 Inter-Maxillary suture
18 Maxilla
19 Ethmoid bone (Orbital plate)
20 Inferior Orbital fissure
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21 Temporo-Zygomatic suture
22 Superior Orbital suture
23 Fronto-Zygomatic suture
24 Greater wing of the Sphenoid
25 Coronal suture - Fronto-Parietal suture
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26 Lesser wing of the Sphenoid
27 Optic foramen
28 Metopic suture (rare) Fronto-Fronto suture
29 Glabella

13 © A. L. Neill


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THE SKULL
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© A. L. Neill 14



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radiology occipitofrontal
THE SKULL

1 Sagittal suture
2 Lamboid suture (view to the posterior) meeting at
the Bregma

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3 Frontal sinus
5 Supraorbital fissure
7 Fronto-Zygomatic suture
8 Petrous ridge
nd
9 Anterior clinoid process
10 Floor of the hypophyseal fossa + upper apex of
nasal cavity adjacent to nasal sinuses
11 Lateral pterygoid plate
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12 Base of the skull - floor of posterior cranial cavity
13 Foramen rotundum
14 Mastoid process
15 Upper central incisor tooth
16 Mandible
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15 © A. L. Neill


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THE SKULL
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upper and lower views in detail
THE SKULL

radiology occipitofrontal (upper)

1 Frontal sinus

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2 Ethmoid sinus
3 Maxillary sinus
4 Foramen rotundum
7 Posterior clinoid process
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8 Petrous ridge
10 Crista galli
11 Frontal process of zygoma
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12 Middle concha - turbinate
13 Inferior concha - turbinate
14 Lateral border of Greater wing of sphenoid
15 Greater wing of sphenoid
16 Lesser wing of sphenoid
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17 Hard palate
18 Infraorbital foramen
19 Zygomaticofacial foramen
20 Coronoid process of the mandible
21 Soft tissue of lower lid
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22 Pterygoid plates of the sphenoid

17 © A. L. Neill


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THE SKULL
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© A. L. Neill 18



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upper and lower views in detail
THE SKULL

radiology occipitomental (lower)

1 Frontal sinus

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2 Ethmoid sinus
3 Maxillary sinus
4 Foramen rotundum
7 Posterior clinoid process
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8 Petrous ridge
10 Crista galli
11 Frontal process of zygoma
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12 Middle concha - turbinate
13 Inferior concha - turbinate
14 Lateral border of Greater wing of sphenoid
15 Greater wing of sphenoid
16 Lesser wing of sphenoid
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17 Hard palate
18 Infraorbital foramen
19 Zygomaticofacial foramen
20 Coronoid process of the mandible
21 Soft tissue of lower lid
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22 Pterygoid plates of the sphenoid

19 © A. L. Neill


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THE SKULL
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External Skull Inferior

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Base of Skull
THE SKULL

1 Incisive fossa - Alveolare
2 Medial Pterygoid plate and Hamulus (ethmoid)
3 Posterior Nasal aperture

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4 Pterygoid plate (ethmoid)
5 Lateral Pterygoid plate (ethmoid)
6 Zygomatic arch
7 Mandibular fossa
8 External Auditory meatus
9 Styloid process
nd
10 Mastoid process
11 Parieto - Mastoid suture
12 Occipito - Mastoid suture
13 Foramen magnum
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14 External Occipital proturberance
15 Sagittal suture - Parieto - Parieto suture
16 Lambda
17 Lambda suture
18 Superior nuchal line (Occipital)
19 Inferior nuchal line (Occipital)
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20 Occipital condyle
21 Jugular foramen (fossa)
22 Stylo-Mastoid foramen
23 Carotid foramen - Carotid canal
24 Foramen spinosum
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25 Foramen lacerum-Basilar suture
26 Greater Palatine foramen
27 Horizontal plate of Palatine
28 Palatine process of the Maxilla
29 Foramen ovale
30 Alveolon

21 © A. L. Neill


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THE SKULL
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External Skull Inferior

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radiology submentovertical view
THE SKULL

1 Nasal septum (vomer and perpendicular plate of
the ethmoid)
2 Posterior border of vomer

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3 Maxillary sinus
4 Ethmoid sinus
5 Greater palatine foramen
6 Lesser palatine foramen
7 Sphenoid sinus
8 Posterior orbital margin - greater wing of the
nd
sphenoid
9 Posterior boundary of the maxillary sinus
10 Zygomatic arch
11 Lesser wing of the sphenoid
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12 Head of mandible condyloid process
13 Foramen ovalae
14 Foramen spinosum
15 Spine of the sphenoid
16 Foramen lacerum
17 Clivus - base of the occipital and sphenoid bones
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18 Eustachian tube - (pharyngotympanic tube)
19 Carotid canal
20 Jugular foramen
21 Stylomastoid foramen
22 Anterior arch of the atlas (C1)
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23 Odontoid process of axis (C2)
24 Occipital condyles
25 Foramen magnum
26 Canaliculus for tympanic nerve
27 Inner and outer tables of the skull - Diploe

23 © A. L. Neill


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THE SKULL
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External Skull Lateral

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1 Frontal bone - Temporal ridges for attachment of
THE SKULL

Temporalis
2 Bregma - Coronal suture
3 Parietal bone

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4 Parieto-Temporal suture
5 Lambda - Occipito-Parietal suture
6 Occipital bone - Occipitum
7 Occipito-Mastoid suture
8 Porion - upper margin of external auditory meatus
9 Mastoid process
nd
10 Temporal bone
11 Styloid process
12 Zygomatic arch
13 Ramus of the Mandible
14 Body of the Mandible
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15 Gnathion
16 Maxilla
17 Zygoma
18 Prosthion
19 Rhinion
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20 Nasal bone
21 Lacrimal bone
22 Nasion
23 Glabella
24 Frontal bone
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25 © A. L. Neill


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THE SKULL
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External Skull Lateral / oblique

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radiology
THE SKULL

1 Coronal suture
2 Impression for Middle meningeal artery
3 Lambdoid suture

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4 Wormian bone - Extrasutural bone
5 Styloid process
6 Posterior wall of Nasopharynx
7 Clivus - (base of Sphenoid and Occiptal bones)
8 Hypophyseal fossa
9 Sphenoid sinus
nd
11 Posterior Air cells in the Ethmoid - Ethmoid sinus
12 Anterior Air cells in the Ethmoid - Ethmoid sinus
13 Frontal sinus
14 Zygoma - frontal process
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15 Maxilla - malar process
16 Zygoma - Arch
17 Posterior border of the Maxillary sinus
18 Hard palate - Palatine bone
19 Alveolar bone in Maxilla
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20 Pterygoid plates
21 Soft tissue of Soft Palate and Uvula
22 Mandibular canal
23 Head of Mandible
24 Coronoid process of Mandible
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THE SKULL
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External Skull Posterior

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1 Sagittal sinus
THE SKULL

2 Parietal foramen
3 Lambda Pareito - Occipital suture
4 Occipital bone

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5 Lambdoid suture
6 Superior nuchal line
7 Highest nuchal line
9 Mastoid process
10 External Occitipal protruberance
nd
11 Inferior nuchal groove
12 Superior nuchal groove
13 Sutural bones - Inca
14 Euyron
15 Parietal bone
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rA
©D

29 © A. L. Neill


eill
THE SKULL
aN
nd
ma
rA
©D

© A. L. Neill 30


External Skull Superior

eill
1 Occipital bone
THE SKULL

2 Lambdoid suture - Occipito-Parieto suture
3 Parietal eminence - Euryon
4 Frontal bone

aN
5 Bregma
6 Coronal suture
7 Parietal bone
8 Sagittal suture
9 Lambda
nd
ma
rA
©D

31 © A. L. Neill


eill
THE SKULL
aN
nd
ma
rA
©D

© A. L. Neill 32


Internal Skull Inferior

eill
Skull cap
THE SKULL

1 Lambda
2 Lambdoid suture
3 Parietal foramen

aN
4 Diploe
5 Bregma
6 Coronal suture
7 Frontal crest and Diploe - inner and outer tables of
the skull bone
8 Frontal bone
nd
9 Depressions for arachnoid granulations
10 Grooves for middle meningeal vessels
11 Parietal bone
12 Sagittal suture
ma

13 Groove for superior sagittal sinus
14 Occipital bone
rA
©D

33 © A. L. Neill


eill
THE SKULL
aN
nd
ma
rA
©D

© A. L. Neill 34


Internal Skull Inferior

eill
Internal base – Cranial fossa
THE SKULL

1 Cribiform plate
2 Frontal sinus
3 Crista Galli

aN
4 Orbital plate of Frontal bone
5 Jugum of Sphenoid
6 Optic canal
7 Lesser wing of the Sphenoid bone
8 Anterior Clinoid process
9 Foramen rotundum
nd
10 Foramen lacerum
11 Foramen ovale
12 Foramen spinosum
13 Dorsum sellae
ma

14 Internal acoustic meatus
15 Jugular foramen
16 Foramen magnum

A POSTERIOR FOSSA
B MIDDLE FOSSA
rA

C ANTERIOR FOSSA
©D

35 © A. L. Neill


eill
THE SKULL
aN
nd
ma
rA
©D

© A. L. Neill 36


Ethmoid bones

eill
Anterior / Lateral / Medial / Superior

Description - Light spongy bone the size and shape of an ice
cube, located between the 2 orbital cavities.

aN
1 Ethmoidal labyrinth containing air cells
(part of the Ethmoid sinus) continuous with the
Sphenoid sinus
2 Crista Galli
3 Orbital plate of Ethmoid bone (part of the Orbital
cavity)
nd
4 Middle Nasal concha
BONES OF THE SKULL

5 Jugum of Sphenoid - Jugum Sphenoidale
(Bridge connecting the 2 wings of the Sphenoid
bone)
ma

6 Perpendicular plate of the Palatine bone
7 Uncinate process
8 Ala (of Crista Galli)
9 Anterior groove (on the Ethmoid)
10 Posterior groove (on the Ethmoid)
11 Cribiform plate (entrance for the Olfactory nerve)
rA

12 Vomer
©D

37 © A. L. Neill


Anterior

eill
Lateral

aN
nd

BONES OF THE SKULL
Medial
ma
rA

Superior
©D

© A. L. Neill 38


Frontal bones Anterior / Lateral / Inferior

eill
Description - Unpaired largest and very robust anterior bone
forming the forehead - horizontal section forming the roof of
the orbit.

aN
1 Frontal tuberosity - Frontal bossing
2 Superciliary arch
3 Supraorbital margin and notch
4 Nasal spine - medial to articulation with Lacrimal
bones
5 Superior and inferior temporal lines
nd
6 Superior Orbital plate - pars orbitalis
BONES OF THE SKULL

7 Frontal and Ethmoid air cells - Frontal sinus
8 Posterior Ethmoidal foramen
9 Anterior Ethmoidal foramen
10 Zygomatic process
ma

11 Supra - Orbital notch or foramen
12 Lacrimal fossa
13 Metopic suture - frontal suture, Glabella
14 Frontal squama
15 Ethmoidal notch
rA
©D

39 © A. L. Neill


eill
aN
nd

BONES OF THE SKULL
ma
rA
©D

© A. L. Neill 40


Hyoid bone

eill
Description - Small U-shaped bone. Attached to the styloid
processes via ligaments, this bone has no articulations and is
not normally broken in normal trauma. It may be broken in
hanging and strangulation.

aN
1 Body of hyoid
2 Greater horn (cornu)
3 Lesser horn (cornu)
nd
BONES OF THE SKULL

ma
rA
©D

41 © A. L. Neill


eill
aN
nd

BONES OF THE SKULL
ma
rA
©D

© A. L. Neill 42


Mandible Lateral / Posterior

eill
Description - The lower jaw bone joins the skull via a single
paired joint the temporomandibular joint (TMJ) via the
condyles and a cartilaginous plate in the Temporal fossa.

aN
Primary function - mastication.

1 Mandibular notch
2 Pterygoid fovea
3 Head of Mandible - Condyle - Condylar process
4 Neck of Mandible
nd
5 Posterior border of ramus of mandible
BONES OF THE SKULL

6 Ramus - Vertical ramus
7 Angle of mandible
8 Oblique line
9 Inferior border
ma

10 Body - Horizontal ramus
11 Base
12 Mental foramen
13 Mental tubercle - Gnathion
14 Mental protuberance
rA

15 Alveolar bone surrounding teeth
16 Anterior border of ramus
17 Coronoid process - Endocoronial ridge
18 Mandibular foramen
19 Lingula
©D

20 Superior and inferior mental spines
21 Digastric fossa
22 Mylohyoid line
23 Mylohyoid groove
24 Extramolar sulcus
25 Infradentale

43 © A. L. Neill


eill
aN
nd

BONES OF THE SKULL
ma
rA
©D

© A. L. Neill 44


Mandible Anterior

eill
radiology
orthopantomogram = OPG

Used to show mandibular fractures and an overview of
sinuses and complete dentition

aN
1 Central incisor
2 Lateral incisor
3 Canine
4 First premolar
5 Second premolar
nd
6 First molar
BONES OF THE SKULL

7 Second molar
8 Pulp chamber
9 Coronoid process
10 Head of mandible
ma

11 Zygoma
12 Maxillary sinus
13 Anterior nasal spine of maxilla
14 Vomer (nasal septum)
15 Sites for the third molar
rA

16 Hard palate
©D

45 © A. L. Neill


eill
aN
nd

BONES OF THE SKULL
ma
rA
©D

© A. L. Neill 46


Mandible Lateral

eill
radiology
Showing relationship to surrounding soft tissue

1 Head of mandible – Condylar process
2 Neck of the Mandible

aN
3 Hard Palate
4 Soft Palate
5 Anterior notch of the Atlas (C1)
6 Odontoid process of the Axis (C2) – Dens
7 Posterior aspect of the tongue
8 Retropharyngeal sac
nd
9 Epiglottis
BONES OF THE SKULL

10 Vallecula - fold anterior to epiglottis
11 Hyoid bone
ma
rA
©D

47 © A. L. Neill


eill
aN
nd

BONES OF THE SKULL
ma
rA
©D

© A. L. Neill 48


Mandibular joint

eill
Temporo-Mandibular joint (TMJ) Lateral
radiology
Open - upper
Shut - lower

aN
1 Head of mandible – Condylar process
2 Neck of the Mandible
3 Coronoid process
4 Zygomatic arch
5 External auditory meatus + Handle of the malleus
6 Articular cubicle
nd
BONES OF THE SKULL

7 Tympanic plate
8 Mastoid process
9 Groove for posterior belly of Digastric muscle
10 Mandibular fossa
ma

11 Greater wing of the sphenoid (basal surface)
12 Lesser wing of the sphenoid
rA
©D

49 © A. L. Neill


eill
aN
nd

BONES OF THE SKULL
ma
rA
©D

© A. L. Neill 50


Maxilla / Maxillae Bones

eill
Anterior / Lateral / Medial

Description - Paired bones which form the dominant portion
of the face and hold the upper teeth. The “overgrowth” of the
maxilla is often the reason for orthodontic treatment.

aN
1 Frontal process
2 Medial Orbital surface
3 Infra-Orbital margin
4 Zygomatic process
5 Infra-Orbital foramen
nd
6 Nasal notch
BONES OF THE SKULL

7 Nasal crest
8 Anterior nasal spine
9 Alveolar bone around teeth
ma

10 Tuberosity
11 Infra-Temporal surface
12 Orbital surface
13 Palatine process
14 Ethmoid crest
15 Middle meatus
rA

16 Conchal crest
17 Anterior Nasal spine
18 premaxillary suture is here - fuses with completed jaw
growth Incisive canal supported by the canine jugun
19 Greater Palatine canal - groove
©D

20 Articulating surface - with Palatine bones
21 Maxillary hiatus continues with the sinus
22 Nasal Lacrimal process
23 Alveolus -bone containing tooth root
24 Canine jugun
25 Inferior meatus

51 © A. L. Neill


eill
aN
nd

BONES OF THE SKULL
ma
rA
©D

© A. L. Neill 52


Maxilla / Maxillae Bones Inferior

eill
1 Incisive fossa
2 Median Palatine suture (Inter-Maxillary suture)
3 Groove for greater Palatine vessels
4 Palatine process of the Maxilla
5 Greater Palatine foramen

aN
6 Palato-Maxillary suture
7 Inter-Palatine suture
8 Inferior Orbital fissure
9 Lesser Palatine foramen
10 Posterior Nasal spine
11 Foramen spinosum
nd
12 Foramen ovale
BONES OF THE SKULL

13 Carotid canal
14 Foramen lacerum
15 Occipital condyle
ma

16 Foramen magnum
17 Palato-vaginal canal
18 Pharyngeal tubercle
19 Ala of Vomer
20 Medial Pterygoid plate
21 Lateral Pterygoid plate
rA

22 Infratemporal crest of Sphenoid
23 Zygomatic arch
24 Pyramidal process of the Palatine bone
25 Maxillary tuberosity
26 Left Third Molar tooth - LM3
©D

27 Left Second molar tooth - LM2
28 Left First molar tooth - LM1
29 Left Second premolar tooth - LP2
30 Left First premolar tooth - LP1
31 Left Canine tooth - LC1
32 Left Second incisor tooth - LI2
33 Left First incisor tooth - LI1
53 © A. L. Neill


eill
aN
nd

BONES OF THE SKULL
ma
rA
©D

© A. L. Neill 54


Nasal Bones

eill
External (rotated 180 degrees to show)
Internal (below)

also see the Nasal Cavity to see the Nasal bones in situ

aN
Description - Small thin rectangular paired bones below the
Glabella, the inferior edges form the top margin of the nasal
aperture. Inferior nasal conchae - small snail shaped fragile
bones extending along the lateral walls of the nasal cavity on top
of the palatines.
nd
1 Articulation surface with Frontal bone and Lacrimal bone
BONES OF THE SKULL

2 Articuation surface with the Maxilla
3 External surface
4 Notch for external nasal nerve
ma

5 Foramen for Veins / Venous foramen
6 Articulation with other nasal bone (here - Right nasal bone)
7 Internal surface
8 Groove for anterior Ethmoidal nerve
rA
©D

55 © A. L. Neill


Occipital bone External / internal

eill
Description - Large bowl like bone with a hole at the infero-
posterior portion of the skull. Articulates with vertebral
column C1 and C2.

aN
1 Superior angle
2 Highest nuchal line
4 Inferior nuchal line
5 Mastoid margin
6 Jugular process
nd
7 Condylar fossa
BONES OF THE SKULL

8 Occipital condyle
9 Foramen magnum
10 Hypoglossal canal
11 Condylar canal
ma

12 Lateral surface
13 Lateral angle
14 External / Internal Occipital crest
15 Squamous surface
16 External / Internal Occipital protuberance
rA

17 Lamboid margin
19 Cerebral fossa
20 Groove for transverse sinus
21 Attachment for Tentorium Cerebelli
©D

22 Groove for superior sigmoid sinus
23 Jugluar notch
24 Jugular tubercle
25 Attachments for Falx Cerebri
26 Opisthion
27 Basion
28 Occipital sulcus - Sagittal sinus

57 © A. L. Neill


Palatine bones (Left)

eill
Anterior / Lateral / Medial / Posterior / Sagittal

Description - Delicate paired small bones L-shaped bones
forming the palate and the floor of the nasal cavity.

aN
1 Perpendicular plate - vertical plate
3 Maxilla
4 Orbital process
5 Spheno-Papalatine notch
6 Spenoidal process - Pterygo-Palatine canal
nd
7 Horizontal plane
BONES OF THE SKULL

8 Pyramidal process - Posterior nasal spine
9 Palatine bone
10 Sphenoidal process
ma

11 Maxillary process
12 Ethmoidal crest
13 Greater Palatine groove
14 Conchal crest
rA
©D

59 © A. L. Neill


Parietal bone (Left) External / Internal

eill
1 Superior Temporal line
2 Parietal eminence
3 Articulation with the Occipital bone
(Lambdoid suture)

aN
4 Articulation with the Temporal bone (Mastoid)
Parieto-Mastoid suture
5 Articulation with the Temporal (Squamous)
Temporo-Parietal suture
6 Articulation with the Sphenoid (Greater wing)
Spheno-Parietal suture
nd
7 Articulation with the Frontal bone Coronal suture
BONES OF THE SKULL

8 Inferior Temporal line
10 Frontal angle
11 Sphenoidal angle
ma

12 Groove for frontal branch of Middle Meningeal
vessels
13 Groove for parietal branch of Middle Meningeal
vessels
14 Mastoid angle
rA

15 Groove for sigmoid sinus
16 Occipital angle
17 Articulation between Parietal bones Sagittal suture
18 Arachnoid granulations - Granular fovea
19 Groove for transverse sinus
©D

61 © A. L. Neill


Sphenoid Anterior / Posterior

eill
Description: A single wedge-shaped bone consisting of four
parts: the central body; the lateral greater wings, the
medial lesser wings and the lower Pterygoid plates. The
bone looks like a bat in flight and is the centre piece of the

aN
skull.

1 Articulation with Left Temporal bone
2 Orbital surface
3 Infratemporal crest
4 Body of the Sphenoid
nd
5 Openings for sphenoidal sinuses
BONES OF THE SKULL

6 Lesser Wing
7 Squamosal suture - Articulation
with Right Temporal bone
8 Superior orbital fissure
ma

9 Foramen rotundum
10 Pterygoid canal
11 Rostrum
12 Vaginal process
rA

14 Pterygoid hamulus
15 Pterygoid notch
16 Lateral Pterygoid plate
17 Pterygoid process
18 Sphenoid spine
©D

19 Cerebral surface of the Greater Wing
21 Posterior Clinoid process
22 Dorsum Sellae
23 Scaphoid fossa
24 Occipital surface

63 © A. L. Neill


Temporal bone (Left) External / Inferior / Internal

eill
Description - Paired bones which are involved in both the
wall and the base of the skull. They contain the auditory
ossicles and form the only joint with the mandible.
1 Suprameatal triangle
2 Groove for middle Temporal artery
3 Parietal notch

aN
4 Squamo-Mastoid suture
5 Mastoid area
6 Mastoid process
7 Sheath of Styloid process
8 Styloid process
9 Tympanic part l
0 External Acoustic meatus / anterior border (bony ear
nd
hole)
BONES OF THE SKULL

11 Tympanosquamosal (squamotympanic) fissure
12 Mandibular fossa
14 Articular tubercle
15 Postglenoid tubercle
ma

16 Squamous part - Squama
17 Stylomastoid foramen
18 Mastoid notch - Digastric groove
19 Occipital groove
20 Jugular surface
21 Jugular fossa
22 Canaliculus (opening) for Tympanic nerve
rA

23 Petrous part
24 Carotid canal
25 Edge of Tegmen Tympani
26 Groove for the Middle Meningeal vessels
27 Groove for the superior Petrosal sinus
28 Articulation with the greater wing of the Sphenoid
©D

Spheno-Temporal suture
30 Groove for the Middle Meningeal vessels
31 Internal Acoustic meatus
32 Articulates with the Occipital bone
33 Aqueduct of the Vestibule
34 Mastoid foramen
35 Groove for sigmoid sinus - Sigmoid sulcus
36 Arcuate eminence
65
37 Articulates with the parietal bone - Temporoparietal Neill
© A. L.
suture


Vomer Lateral / Posterior / in situ

eill
Description - A single small narrow frail plough-shaped
midline bone. Deviation of this bone may obstruct the nasal
airways.

aN
1 Ala (Alae)
2 Articulation with Maxillae and Palatine
Maxillovomer suture / palatinovomer suture
3 Groove for the nasopalantine nerves and vessels
4 Articulation with nasal cartilages
5 Articulation with Sphenoid bone
nd
6 Articulation with the Ethmoid plate
BONES OF THE SKULL

7 Perpendicular plate of the Ethmoid
8 Body of Vomer
9 Maxillae areolar bone
10 Medial pterygoid plate
ma

11 Frontal bone
12 Sphenoid sinus
13 Anterior of nasal bones
14 Frontal sinus
rA
©D

67 © A. L. Neill


Zygoma Antero-Lateral / Postero-Medial

eill
Description - Paired cheek bones which form the
prominent corners of the face under the orbital rim.

1 Frontal process

aN
2 Zygomatico-Facial formina
3 Articulation with the Frontal bone
4 Articulation with the Sphenoid
5 Zygomatico-Orbital foramina
6 Articulation with Maxilla
7 Zyomatico-Temporal foramina
nd
8 Temporal process
BONES OF THE SKULL

9 Maxillary process
10 Orbital surface
ma
rA
©D

69 © A. L. Neill


Anterior Cranial Fossa

eill
Superior view from the top

1 Frontal sinus
2 Frontal crest
3 Foramen Caecum

aN
4 Cranionasal exit of the anterior ethmoidal nerve
5 Slit for the process of the dura mater
6 Anterior Ethmoidal groove
7 Concealed entry for the anterior Ethmoidal nerve
8 Posterior Ethmoidal groove
9 Concealed entry for the posterior Ethmoidal nerve
nd
10 Jugam Sphenoidale
Optic canals
13 Fronto-Sphenoid suture
ma

15 Vascular foramen
16 Diploe
17 Orbital plate of the Frontal bone
18 Crista Galli
rA
CAVITIES OF THE SKULL

©D

71 © A. L. Neill


Maxillary Sinus (Left) Sagittal

eill
1 Frontal sinus
2 Anterior Ethmoidal foramen
3 Orbital plate of Ethmoid
4 Posterior Ethmoidal foramen

aN
6 Pterygo-Maxillary fissure
7 Perpendicular plate of the Palatine
8 Alveolar processes of the Maxilla
9 Maxillary Sinus - opened
10 Inferior concha, Maxillary process
nd
11 Anterior Nnasal spine
12 Uncinate process of the Ethmoid
13 Nasal bone
14 Lacrimo-Maxillary suture
15 Supra-Orbital foramen
ma

16 Frontal bone
rA

©D

Description: Maxilla - sinuses within this bone -particularly
around the teeth may cause toothache, complicate
endodontic (root canal) treatment; or act as a conduit for
tooth/nasal/other infection to enter the blood stream.

73 © A. L. Neill


Middle Cranial Fossa (Left)

eill
Superior view from the top

2 Superior Orbital fissure
3 Middle Clinoid process

aN
4 Optic canal
6 Hypophysial fossa
7 Posterior Clinoid process
8 Dorsum Sellae
9 Foramen lacerum
nd
10 Trigeminal impression Foramen rotundum
12 Groove for superior petrosal sinus
13 Groove for greater petrosal nerve
14 Diploe
ma

15 Arcuate eminence
16 Tegmen typani
17 Temporal bone
18 Groove for the Parietal branch of the middle
Meningeal vessels
rA

©D

75 © A. L. Neill


Nasal Cavity - dissected to show Right nasal cavity and

eill
inferior nasal conchae
Para - Sagittal section of Right Nasal cavity
looking in through the Right side of the nose to show sinuses
around the area

aN
1 Semilunar hiatus
2 Ethmoid bulla
3 Air cells of Ethmoid sinus
4 Sphenoidal sinuses
5 Spheno-Palatine foramen
6 Perpendicular plate of the palatine
nd
7 Inferior nasal concha and meatus
8 Opening of the maxillary sinus
9 Uncinate process of Ethmoid bone
10 Right Frontal sinus
ma

Note middle and superior nasal conchae have been dissected
and removed.
rA

©D

Description: inferior nasal conchae - small paired frail bones
extending along the lateral walls of the nasal cavity. Involved
in olfaction, humidification. Highly vascularized and when the
soft tissue surrounding this is swollen, it may cause nasal
obstruction and sinuses. Please note when "picking one's
nose" the finger never reaches the nasal conchae, stopping
just short of this area.

77 © A. L. Neill


Nasal Cavity

eill
dissected to show lateral wall of right nasal cavity
Sagittal section of Lateral Right nasal cavity
looking in to the lateral side of the right side of the nose

1 Middle concha

aN
2 Middle concha meatus
3 Superior concha
4 Superior concha meatus
5 Sphenoid sinus
7 Spheno-Palatine foramen
nd
8 Perpendicular plate of Palatine bone
10 Incisive fossa and canal
11 Inferior concha and meatus
12 Maxilla
ma

13 Lacrimal bone
14 Nasal bone
15 Right Frontal sinus
16 Left Frontal sinus
rA

©D

79 © A. L. Neill

The A to Z of Skull Bones

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