CRANIUM (SKULL):INDIVIDUAL CRANIAL BONES
NEUROCRANIUM
Prof. Dr.Selda Önderoğlu
Bones of the cranium (skull) are studied in two groups:
• Bones of the NEUROCRANIUM- Bones which enclose and protect the brain.
• Bones of the SPLANCHNOCRANIUM
(VISCEROCRANIUM)- Bones which form the facial skeleton. They surround at the same time the oral , nasal and orbital cavities and form
boundaries around the deep structures of the face.
• This division is actually arbitrary as there is an overlap between these two groups in the
formation of certain parts of the skull.
BONES OF THE NEUROCRANIUM
• TEMPORAL BONES (PAIRED)
• SPHENOID BONE (SINGLE)
• FRONTAL BONE (SINGLE)
• OCCIPITAL BONE (SINGLE)
• PARIETAL BONES (PAIRED)
Neurocranium
• frontal
• parietal
• occipital
• temporal
• Sphenoid
TEMPORAL BONES
• Take place one on each side of the skull.
• The temporal bones take part in the
formation of the sides and base of skull.
• Each temporal bone has several parts:
a) Squama (leaf) b) Tympanic
c) Petromastoid which can be divided into a petrous (pyramis) part and a mastoid
part.
TEMPORAL BONE
temporal bone; parts:
-squamous, -petromastoid, -tympanic,
Styloid process
TYMPANIC PART & SQUAMA
Squama of temporal bone
• Connected to: parietal+occipital+sphenoid bones
• Externally convex, internally concave
• External surface of squama:
- Squamous suture: with parietal bone
-zygomatic process: with temporal process of zygomatic bone forms the zygomatic arch
-mandibular fossa- ant.ly bounded by the articular tubercle
-part of the Temporal fossa is related to temp.bone
Mandibular fossa
İnner surface of squama
• Groove for the middle meningeal artey
Tuberculum articulare
Processus zygomaticus
Fossa
mandibularis
Processus mastoideus
Porus
acusticus
externus
Porus acusticus internus
MASTOID PARTof temporal bone
• It forms the posterior part of the temporal bone.
• Important features:
-Mastoid process.
-Mastoid notch.
- Mastoid foramen ( on the outer+inner surface ) -Groove for sigmoid sinus ( inner surface )-
-Mastoid air cells ( antrum-means entrance ): within the
mastoid part
PETROUS PART (PYRAMIS)
• It lies at the base of the skull between the sphenoid and occipital bones. It is directed medially, forwards and slightly upwards.
• It has an apex
• and three surfaces:
-superior (anterior) -posterior,
-inferior.
APEX
İmportant features:
• TRIGEMINAL IMPRESSION.
Contains the
trigeminal (Gasserian) ganglion.
• INTERNAL
APERTURE OF THE CAROTID CANAL.
Transmits the internal carotid artery.
Trig.imp.
SUPERIOR (ANTERIOR) SURFACE
Important features:
-ARCUATE EMINENCE -TEGMEN TYMPANI
-Opening of facial canal
Arcuate eminence
mpani
POSTERIOR SURFACE
• Important features:
-INTERNAL AUDITORY MEATUS (APERTURE)
-EXTERNAL APERTURE (OPENING) OF AQUEDUCTUS VESTIBULI
-SUBARCUATE FOSSA
ınternal acoustic meatus
Subarcuate fossa
INFERIOR SURFACE
• Important features:
-EXTERNAL APERTURE OF THE CAROTID CANAL.
- Musculotubal canal ( behind ext.ap.of carot.can.) -JUGULAR FOSSA & JUGULAR NOTCH
(INCISURE). ( behind carot.can. ) -STYLOID PROCESS.
-STYLOMASTOID FORAMEN ( behind
stylomast.for .)TRANSMITS THE FACIAL NERVE)
Styl.proc.
Stylomastoid foramen External aperture of carotid canal
Jugular fossa
Mandibular fossa
Articular tubercle
THE SPHENOID BONE
• It is a single butterfly shaped bone located at the base of the skull, anterior to the temporal bones and basilar part of the occipital bone.
• It takes part in the formation of the sides and base of skull as well as the orbital and nasal cavities.
• Parts:
- Body
- A pair of greater wings
- A pair of lesser wings.
sphenoid bone:
body
greater wing
lesser wing
pterygoid process
Foramen rotundum
Canalis
pterygoideus Superior orbital
fissure
GREATER WINGS (ALAE)
• KEY WORDS:
-PTERYGOID PROCESS: has Lateral and medial plates (lateral pterygoid lamina&
medial pterygoid lamina)
-Pterygoid notch: bw. Two lamina
-Tip of medial pterygoid plate: pterygoid hamulus
-orıfıce (openıng) of the pterygoıd canal.
Anterior view of sphenoid bone
GREATER WING
• Each greater wing has three surfaces:
• CEREBRAL SURFACE
• ORBITAL SURFACE
• LATERAL SURFACE
CEREBRAL SURFACE
KEY WORDS:
Anteromedially is the ROUND FORAMEN
(ROTUNDUM) which transmits the MAXILLARY nerve.
Posterolateral to the rotundum is the OVAL FOR.
which transmits the MANDIBULAR nerve.
Adjacent to the oval for. is the FOR. SPINOSUM which transmits the MIDDLE MENINGEAL
artery.
sphenoid bone-cerebral surface
LATERAL SURFACE
• This surface is divided into superior TEMPORAL SURFACE and inferior INFRATEMPORAL SURFACE.
• The lateral surface takes part in the
formation of the sides of the skull.
ORBITAL SURFACE
• This surface is directed anteriorly and
medially and forms the posterior part of
the lateral wall of the orbital cavity.
THE LESSER WINGS
They are two triangular plates which project from the anterosuperior part of the body and end in sharp points.
• It is connected to the body by two roots.
• Each lesser wing has an anterior border and a posterior border.
• KEY WORDS:
• OPTIC CANAL (which transmits the OPTIC nerve & OPHTHALMIC artery.
• ANTERIOR CLINOID PROCESS.
SUPERIOR ORBITAL FISSURE
• Leads from the cranial cavity into the orbital cavity.connects both cavities.
• Boundaries:It is bounded medially by the
body of the sphenoid; above by the lesser
wing, below by the greater wing. Laterally
it is completed by the frontal bone.
THE BODY
• The body is cubical. Within the body is an air sinus called the sphenoid sinus.
• KEY WORDS:
• CAROTID SULCUS.
• TUBERCULUM SELLAE.
• HYPOPHYSEAL FOSSA.
• DORSUM SELLAE. The three are collectively called the SELLAE TURCICA.
• MIDDLE and POSTERIOR CLINOID PROCESSES.
• SPHENOIDAL CREST- at the midline of the ant. surface
• Tip of sphenoidal crest ROSTRUM.
• Carotid sulcus: at the Lat. Sides of the body
• Sphenoidal sinus: within the body
Hypophyseal fossa
Post.clinoid process
THE FRONTAL BONE
It is a single bone and it forms the skeleton of the forehead.
Parts of the frontal bone are:
1- Squama.
2- Orbital parts.
3- Nasal part.
FRONTAL SQUAMA
• It is a flat bone which is externally convex and internally concave.
• EXTERNAL SURFACE KEY WORDS:
• Frontal tuber (tuberosity).
• Temporal line.
• Superciliary arches.
• Glabella.
• Supraorbital margin.This margin laterally ends as the zygomatic process. Medially it contains a notch or foramen called the supraorbital notch or foramen.
• Within the squama are located the frontal sinuses.
Temporal line
FRONTAL SQUAMA INNER SURFACE
INTERNAL SURFACE KEY WORDS:
• Sulcus for superior sagittal sinus ( in the
midline)
• Frontal crest ( inferior to sulcus for sup. Sag. Sinus)
• Foramen caecum: located where frontal crest
ends
Sulcus for sup.sag.sin.
Frontal crest
THE ORBITAL PARTS
• Consists of two lamınae separated by a wide notch called the ETHMOIDAL NOTCH.
• Anterolaterally is a shallow fossa called FOSSA FOR THE LACRIMAL GLAND.
• The ethmoidal notch is occupied in the
articulated skull by the cribriform lamina of the ethmoid bone.
• On the lateral margins of the notch are located several air cells.
• Anteriorly, lateral to the nasal spine, are the
openings of the frontal sinuses.
THE OCCIPITAL BONE
• It is a single bone which forms a large part of the back & base of skull.
• It consists of four parts which together enclose a large foramen called the
FORAMEN MAGNUM.
• The parts of the bone are:
Squama.
Two lateral parts.
Basilar part.
OCCIPITAL SQUAMA
• It is externally convex, internally concave.
• EXTERNAL SURFACE KEY WORDS:
• EXTERNAL OCCIPITAL PROTUBERANCE.
• EXTERNAL OCCIPITAL CREST.
• HIGHEST (SUPREME) NUCHAL LINE.
• SUPERIOR NUCHAL LINE.
• INFERIOR NUCHAL LINE.
Ext. occ.prot..
crest
