The SkullEhab ZAYYAN, MD, PhD

The skull is composed of separate bones united at immobile joints called sutures.

Sutural ligaments: between the bones TMJ: the only mobile joint in the skull Skull bones: external and internal tables of

compact bone separated by spongy bone called diplo

Outer and inner periosteum

Anatomical positionFrankfort horizontal plane

The cranium is in the anatomical position when the inferior margin of the orbit and the superior margin of the external acoustic meatus lie in the same horizontal orbitomeatal or Frankfort horizontal plane, a standard craniometric reference

Cranium (Skull)

1. Neurocraniuma) Clavariab) Cranial base

2. Viscerocranium (face bones)

Total : 22 bones

NeurocraniumFormed from the mesenchyme of the neural

crest

Clavaria and skull base (basocranium)

Frontal bone 1

Parietal bones 2

Occipital bone 1

Temporal bones 2

Sphenoid bone 1 Ethmoid

bone 1

Frontal

Clavaria

Frontal Parietal Occipital Temporal

Skull base

Occipital Temporal Sphenoid Ethmoid

Frontal Parietal Occipital Temporal Sphenoid Ethmoid

Frontal Ethmoid Sphenoid Temporal Occipital Parietal

Viscerocranium(Facial skeleton)

Develop from the embryonic mesenchymeof the pharyngeal arches

Consists of the bones surrounding the mouth (upper and lower jaws), nose/nasal cavity, and most of the orbits (eye sockets or orbital cavities)

Facial bones (viscerocranium)

1Mandible

2Inferior conchae

2Palatine bones

1Vomer

2Lacrimal bones

2Nasal bones

2Maxillae

2Zygomatic bones

Maxilla Mandible Zygoma Nasalis Lacrimal

Maxilla Mandible Zygoma Nasalis Lacrimal

Maxilla Palatine Zygoma Ethmoid

and vomer

Mid- sagittal sectionmedial nasal wall

Ethmoid Vomer Maxilla Palatine Nasalis

Lateral nasal wall

Nasalis, maxilla, ethmoid, inferior concha, palatine

The maxillae contribute the greatest part of the upper facial skeleton, forming the skeleton of the upper jaw, which is fixed to the cranial base.

The mandible forms the skeleton of the lower jaw, which is movable because it articulates with the cranial base at the temporomandibular joints (TMJs).

Pneumatized bones of the skull

Several bones of the cranium are pneumatized bones, which contain air spaces (air cells or larger sinuses), presumably to decrease their weight. The total volume of the air spaces in these bones increases with age.

Frontal Ethmoid Sphenoid Maxilla Temporal

Paranasal sinuses

Paranasal sinuses x-ray

Pneumatization of the temporal bone

Geometric points of the skull

Pterion (G. wing): Junction of the greater wing of the sphenoid, squamous temporal, frontal, and parietal bones; overlies course of anterior division of middle meningeal artery

Lambda (G. the letter L): Point on calvaria at junction of lambdoid and sagittal sutures

Bregma (G. forepart of head): Point on calvaria at junction of coronal and sagittal sutures

Vertex (L. whirl, whorl): Superior point of neurocranium, in the middle with the cranium oriented in anatomical (orbitomeatal or Frankfort) plane

Asterion (G. asterios, starry): Star shaped; located at junction of three sutures: parietomastoid, occipitomastoid, and lambdoid

Glabella (L. smooth, hairless): Smooth prominence; most marked in males; on the frontal bones superior to root of nose; most anterior projecting part of forehead

Inion (G. back of head): Most prominent point of external occipital protuberance

Nasion (L. nose): Point on cranium where frontonasal and internasal sutures meet

Frontal bone

Frontal sinuses

Parietal bones

Parietal bone internal surface

Occipital bone

Occipital bone internal surface

Temporal bone

1. Squamous

2. Mastoid

3. Petrous

4. Styloid

5. Tympanic

Adult skull

Neonatal skull

At birth the mastoid process and the bony external canal of the tympanic part are absent.

Neonatal temporal bone

Squamous part Petrous part Tympanic part

Nasal bones

Anterior nasal aperture

Zygomatic bone

Cheeks prominence Orbital cavities Zygomatic arch Zygomaticofacial& zygomaticotemporalnerve foraminae

Maxilla Upper jaw - anterior

part of hard palate -lateral wall of nasal cavity - floor of orbital cavities

Intermaxillarysuture

Infraorbital foramen Alveolar processes Ant nasal spine Maxillary sinus

Palatine bones

Vomer

Vomer, medial nasal wall

Bony nasal septum Maxillary crest Vomer Perpendicular plate of the ethmoid

Medial nasal wall

Superior and middle nasal conchae: parts of the ethmoid bone

Inferior nasal concha is a separate bone

Inferior concha, lateral nasal wall

Lateral nasal wall

Paranasal sinuses

Paranasal sinuses x-ray

The mandible

Condyle Coronoid process Ramus Body Alveolar process Mental

protuberance Angle

Body of the mandible

Lateral surface Symphysis menti Mental foramen

mental nerve and vessels

Medial surface

Mental spines

genioglossus and geniohyoid

Mylohyoid line Submandibular

fossa Sublingual fossa Digastric fossa

Ramus of the mandible

Coronoid process Condyloid process (head) Neck Mandibular notch Masseter muscle attachment

Mandibular foramen

inferior alveolar nerve and vessels

mandibular canal

mental foramen Lingula : attachment of sphenomandibular

ligament

Anterior view of the skull

Frontal bone Superciliary arches Supraorbital notch Articulation with

maxillae, nasal bones, zygomaticbones

Anterior view of the skull

Orbital margins Sup: frontal bones Lat: zygomatic bones Inf: maxillae Medial: maxillae and frontal bones

Nasal bones and anterior nasal aperture

Maxilla

Intermaxillarysuture

Infraorbital foramen Alveolar processes Ant nasal spine Canine fossa

Zygomatic bone

Cheeks prominence Orbital cavities Zygomatic arch Zygomaticofacial& zygomaticotemporalnerve foraminae

The mandible

Lateral view of the skull

Coronal suture: frontal and parietal bones Sagittal suture: two parietal bones Lambdoid suture: parietal and occiptal bones

Frontal bone Parietal bone Occipital bone-

squamous part Temporal bone:

squamous-tympanic-mastoid- styloid-zygomaticprocess

Greater wing of sphenoid

Pterion The thinnest part of

the lateral wall of the skull

Anterioinferior corner of the parietal bone-greater wing of sphenoid bone

Overlies the anterior division of the middle meningeal artery and vein.

Superior and inferior temporal lines Temporal fossa Infratemporal fossa Pterygomaxillary fissure

Infratemporal fossa

Pterygopalatine fossa

A small space behind and below the orbital cavity

Pterygomaxillary fissure

infratemporal fossa (laterally)

Sphenoplatine foramen

nasal cavity (medially)

Foramen rotundum

skull (superiorly) Inferior orbital fissure

orbit (anteriorly)

Posterior view of the skull

Sagittal suture Lambdoid suture Parietomastoid

suture External occipital

protuberence: attachment to muscles and nuchal ligament

Superior nuchallines

Superior view of the skull

Coronal suture Sagittal suture Lambdoid suture

Inferior view of the skull

Inferior view of the skull- Palate

Hard palate Palatal processes of the maxilla Horisontal plates of palatine bones Incisive fossa and foramen Greater and lesser palatine foramina Choanae (posterior nasal apertures) Vomer

Inferior view of the skull- Sphenoid

Medial pterygoid plates Pterygoid hamulus Lateral pterygoid plates Foramen ovale Foramen spinosum

Temporal Auditory tube: in the

interval between the greater wing of the sphenoid and the petrous part of the temporal bone

Foramen lacerum

Medial end of petrouspart of the temporal -basilar part of the occipital - greater wing of sphenoid.

During life it is closed with fibrous tissue. Few small vessels pass thru it. GSPN may pass too.

Zygomaticprocess

Articular tubercle Mandibular fossa Petrotympanic

fissure: separates the mandibular fossa from the tympanic plate. The chordatympani nerveexists from it

Carotid canal Jugular foramen Styloid process Stylomastoid foramen External acoustic meatus

Suprameatal crest

Suprameatal triangle (Mcewen triangle)

Suprameatal spine (spine of Henle)

Occipital Jugular foramen: notch on the petroustemporal and notch on the occipital bones.

Foramen magnum Basilar part of the

occipital bone Pharyngeal tubercle Occiptal condyles:

articulate with atlas The occiptal canal

passes superior to the condyles

Extarnal occipital protuberence and superior nuchal lines.

Neonatal skull

Large cranium to face ratio Mandible and maxilla are short Bones are mobile on each others and

connected by fibrous tissue or cartilage Anterior fontanelle

: closes at 18 months of age

Posterior fontanelle

: closes at 1 year of age

Mastoid process not present at birth.

Clinical

Fontanelles enables us to: Follow up the progress of growth of the

infant Detect dehydration The state of intracranial pressure Take samples of the CSF

Internal surface of the skullVault of the skull

Coronal, sagittal and lambdoid sutures

Groove for the superior sagittal sinus

Grooves for the branches of the middle meningeal vessels

Granular pits for archnoid granulations

Base of the skull

Anterior cranial fossaSphenoid lesser wing

Middle cranial fossaTemporal bone petrous part

Posterior cranialfossa

Anterior cranial fossa

Frontal bone Frontal crest (attachment for falx cerebri) Lesser wing of the sphenoid Anterior clinoid process (attachment to tentorium

cerebelli) Orbital plates

Cribriform plate of the ethmoid: olfactory nerve bundles Crista galli Foramen cecum (small vein from nose to SSS) Anterior ethmoid foramen: anterior ethmoid nerve and

vessels Posterior ethmoid foramen: posterior ethmoid nerve and

vessels

Middle cranial fossa

Median part: body of sphenoid Lateral part: greater wing of sphenoid and

squamous part of temporal bone

Body of the sphenoid bone

Sulcus chiasmaticus (prechiasmatic groove) Optic canal Tuberculum sella Sella turcica (contains the hypophysis) Dorsum sella Posterior clinoid processes

Optic canal: optic nerve, opthalmic artery

Superior orbital fissure:- lacrimal, frontal, nasociliary branches of

the opthalmic

nerve (V1)- Oculomotor, trochlear, abducent nerves- Superior ophthalmic vein

Foramen rotundum- maxillary nerve

Foramen ovale- mandibular nerve - lesser superficial petrosal nerve - accessory meningeal artery

Foramen spinosum- middle meningeal artery - meningeal branch of the mandibular nerve

Foramen lacerum: usually closed by cartilage and fibrous tissue. Occasionally the GSPN

Carotid canal: internal carotid artery. The artery runs in the side of the sphenoid body to reach the cavernous sinus

Impression of the trigeminal ganglion: lateral to the foramen lacerum, on the apex of the petrous part of the temporal bone

Greater petrosal nerve hiatus

groove for GSPN

passes to foramen lacerum

joins the deep petrosal nerve

nerve of the pterygoid canal (Vidian nerve)

Lesser petrosal nerve hiatus

groove for the lesser petrosal nerve

foramen ovale

otic ganglion in the infratemporal fossa

Posterior cranial fossa

Foramen magnum- Medulla oblangata- Meninges- Vertebral arteries- Spinal roots of the accessory nerves

Jugular foramen- Inferior petrosal sinus-

CN 9, 10, 11- Sigmoid sinus

internal jugular vein

Internal acoustic meatus: facial nerve and vestibulucochlear nerves

Hypoglossal canal: hypoglossal nerve

Groove for the occipital sinus Internal occipital crest Internal occipital protuberance Groove for the transverse sinus Groove for the sigmoid sinus Groove for the superior petrosal sinus Clivus

The Skull Anatomical positionFrankfort horizontal plane Neurocranium Clavaria Skull base Viscerocranium(Facial skeleton)Facial bones (viscerocranium) Slide166Mid- sagittal section medial nasal wallLateral nasal wall Pneumatized bones of the skullParanasal sinuses Slide228Slide229Paranasal sinuses x-ray Pneumatization of the temporal boneGeometric points of the skull Frontal bone Slide175Slide176Frontal sinusesParietal bones Parietal bone internal surfaceOccipital bone Occipital bone internal surfaceTemporal bone Adult skull Neonatal skullNeonatal temporal bone Slide211Slide210Slide234Slide235Slide209Slide212Slide213Nasal bonesZygomatic boneSlide214Maxilla Palatine bonesVomer Vomer, medial nasal wall Medial nasal wall Slide215 Lateral nasal wallParanasal sinuses Paranasal sinuses x-ray The mandibleBody of the mandibleSlide193 Ramus of the mandible Slide81Anterior view of the skullAnterior view of the skull Maxilla Zygomatic boneThe mandibleLateral view of the skull Infratemporal fossa Pterygopalatine fossaSlide241Slide242Posterior view of the skullSuperior view of the skullInferior view of the skullInferior view of the skull- Palate Inferior view of the skull- Sphenoid Slide245Temporal Slide23 Slide24 Occipital Slide261Slide260Slide262Neonatal skull Slide265Slide263Slide264Clinical Internal surface of the skullBase of the skullSlide266Anterior cranial fossa Middle cranial fossaBody of the sphenoid bone Slide269 Slide270 Slide271Slide268Posterior cranial fossa Slide274 Slide70