Middle cranial fossa

By | 14th May 2012

Anterior cranial fossa >Middle cranial fossa > Posterior cranial fossa:

 

Boundaries:

Anteriorly by the post border of the lesser wings of sphenoid, anterior clinoid processes and sulcus chiasmaticus.

Posteriorly by the superior borders of petrous part of temporal and sphenoids dorsum sella.

Laterally by the squamous part of temporal and some part if parietal and greater wings of sphenoid.

Floor of lateral part is formed by greater wing of sphenoid and petrous and squamous parts of the temporal bone.

In the centre, floor is formed by the sella tursica of body of sphenoid.

The middle cranial fossa is deeper and more extensive than the anterior cranial fossa.

Sella tursica:

Te sella tursica is named for its resemblance of the Turkish saddle with its anterior tuberculum sella, central fossa and posterior dorsum sella.

Tuberculum sella:

Arises from the body of the sphenoid, dividing the hypophysial fossa from the sulcus chiasmatis or optic groove.

Hypophysial fossa:

A midline depression contains the pituitary gland (hypophysis cerebri).

Dorsum sellae:

Is a vertical plate between the posterior clinoid process, forming the posterior wall of the fossa.

Posterior clinoid process:

Continuation of the dorsolateral corners of the flat dorsum sella.

Optic groove:

Sulcus chiasmaticus groves the sphenoid bone between optic foramina and the tuberculum sallae. It is so named because it contains optic chiasm, rather than optic nerve.

Optic canal

It is present between the roots of the lesser wings of sphenoid and contains optic nerve, ophthalmic artery and meninges.

Superior orbital fissure:

It is a slit like opening between the lesser and greater wings of the sphenoid. The middle cranial fossa communicates with the orbits by this fissure.

It transmits oculomotor, trochlear: lacrimal, frontal and nasociliary branches of the ophthalmic division of the trigeminal nerve. Plus it contains abducent nerve and ophthalmic nerve.

Foramen rotundum:

It is just below and behind the medial end of the superior orbital fissure .it transmits the maxillary nerve.

Foramen ovale:

It lies posteriolateral to the foramen rotumdum. It transmits the mandibular nerve, emissary veins, lesser petrosal nerve and accessory meningeal vein.

Foramen spinosum:

It lies posteriolateral to the foramen ovale. it transmits the middle meningeal artery.

Foramen lacerum

It lies superiomedially to the foramen spinosum.

It transmit

  • Internal carotid artery with its sympathetic nervous and venous plexus.
  • Carotid sinus.
  • Emissary veins.
  • Nerve to pterygoid canal (contains deep petrosal nerve and greater petrosal nerve).

 

Petrous part of temporal bone:

This part accommodates the semicircular canals of the ear which are responsible for the balancing and equilibrium. So injury to this part can disturb the equilibrium.

Boundaries of Posterior cranial fossa:

Anteriorly the fossa is bounded by the superior border of the petrous part of temporal bone and dorsum sallae.

Posteriorly by the lesser part of the occipital squama.

Floor by squamous conylor and basilar parts of the occipital bone.foramen magnum forms the central part of the floor.

Foramen magnum:

Occupies he central area of the floor and transmits the medulla oblongata and its surroundings meninges, the ascending spinal parts of the accessory nerves and the 2 vertebral arteries

Hypoglossal canal:

Is situated above the anterolateral boundary of the foramen magnum and transmits the hypoglossal nerve, and emissary veins.

Jugular foramen:

Lies between the lower border of the petrous part of the temporal bone and condylar part of the occipital bone. It transmits 9th, 10th, and 11th cranial nerves and the inferior petrosal sinus plus sigmoid sinus.

Internal acoustic meatus:

Pierces the posterior surface of the petrous part of temporal bone and transmits the vestibulocochlear  nerve and facial nerve.

Clivus:

It is slope formed by the basilar part of the occipital bone and posterior part of the sphenoid bone.