The superior surface of the base of skull is comprised of the anterior, middle and posterior cranial fossa.
The anterior cranial fossa is comprised of the frontal bone, the cribriform plate of the ethmoid bone and the lesser wing of the sphenoid.
The bony land marks are the frontal crest + the crista galli.
Frontal Crest attaches falx cerebri. Crista Galli demonstrates the cribriform plate on either side.
The foramina of the anterior cranial fossa are located either a) within or b) adjacent to the ethmoid bone.
Located adjacent to the ethmoid bone
the foramen caecum -
- at the frontoethmoidal suture
- anterior cranial fossa to the nasal cavity
Contents small emissary vein, from nasal mucosa to superior sagittal sinus
- relies on fusion with the fonticullis frontalis (fontanelle between frontal and nasal) to close.
- From the 3rd to 8 weeks of life there is a dural diverticulum going through the foramen, and incorrect closure causes nasoethmoidal encephalocoele.
Located within the ethmoid bone - from anterior cranial fossa to nasal cavity
The cribriform plate
Contents: around 20 foramina,for the olfactory nerve filaments, divided into medial and lateral filament groups + associated dura + ethmoidal nerves and vessels.
The anterior and posterior ethmoidal foramina
Formamina on the lateral aspect of the cribriform plate through which the ethmoidal nerves and vessel run to course downwards through cribriform plate.
The Middle cranial fossa has foramina which are located relative to the sphenoid bone
Foramina of the Lesser wings
Between Lesser and Greater Wings of Sphenoid - superior orbital fissure
Contains Nerves/arteries and Veins to orbit.
Nerves divded based on annulus of zinn.
superior division of v1
inferior division of v1 + parasympathetics
Foramina of the greater wing
Foramen rotundum to pterygopalatine fossa
artery of foramen rotundum
Foramen ovale to infratemporal fossa
Mandibular, accessory meningeal, lesser petrosal, emissary vein*
Foramen spinosum to infratemporal fossa
Contains nerve artery and vein
Middle meningeal artery
Recurrent meningeal branch of mandibular nerve
Junction of the sphenoid - apex of petrous temporal
Filled with connective tissue in the living skull
Artery vein and nerve
Meningeal branch of ascending pharyngeal
Emissary vein. - spread of nasopharyngeal carcinoma
Superficial greater petrosal nerve
Posterior cranial fossa
Temporal bone - internal auditory meatus
Facial/ni/glossopharyeal and laryngeal branch of aica
Between temporal and occipital
inferior petrosal sinus
vagus and accessory nerves
sigmoid sinus - jugular bulb -
meningeal branch of the ascending pharyngeal
Within the Occipital
spinal accessory nerve (the c1-c5 fibres of the accessory)
The spinal part