Anterior Crainal Fossa
Learning Objectives
At the end of the lecture student will able:
Describe the skull bone that forms the anterior cranial fossa.
Demonstrate the foramina and openings present in anterior cranial fossa.
Discuss the part of brain in relation to the anterior cranial fossa.
Interior Of the skull
Cranium is lined internally by endocranium
The thickness of cranial vault is variable
Most of the cranial bones are consist of:
a) an outer table of compact bone which is thick and tough,
b) an inner table of compact bone which is thin & brittle,
c) Diploe which consist of spongy bone filled with Red marrow.
Skull bones derived their blood supply mostly from meningeal arteries. Very little from arteries of the scalp
Internal Surface of the Cranium
The interior of the base of the skull presents natural subdivision into anterior, middle and posterior cranial fossae.
Dura mater is firmly adherent to the floor of the fossae and is continuous with pericranium thru the foramina and fissures.
Internal or Superior Surface of
Base of Skull
Forms floor of cranial cavity
Divided into 3 fossae, called
Anterior
Middle
Posterior cranial fossae
Anterior cranial Fossa
Bounderies :
Anteriorly--- Anteriorly and on the sides by the frontal bone.
Posteriorly: It is separated from the middle cranial fossa by the free posterior border of lesser wing of sphenoid, the anterior clinoid process and anterior margin of sulcus chiasmaticus.
Floor: anteriorly by the cribriform plate of ethmoid bone, posteriorly by the superior surface of anterior part of the sphenoid—jugum sphenoidale.
On each side—orbital plate of frontal bone and is completed posteriorly by the lesser wing of sphenoid.
Anterior Cranial Fossa
Cribriform Plate of the Ethmoid Bone
Separates the anterior cranial fossa from the nasal cavity.
It’s a quadrilateral shape.
Anterior margin articulates with the frontal bone at the frontoethmoidal suture.
Posterior margins articulates with the jugum sphenoidale—posteriolateral corners –posterior ethmoidal canals.
Lateral margins articulates with the orbital plate of the frontal bone: in b/w the suture the anterior ethmoidal canal placed—behind the crista galli.
Olfactory grooves of cribriform plate
Support olfactory bulb
Perforated by foramina for transmission of olfactory nerves &, more rostrally, by a slit for nasociliary nerve
Anterior Cranial Fossa
Frontal crest (of frontal bone)
In midline most anteriorly, on which attaches falx cerebri
Foramen cecum
-- The frontal crest of the frontal bone ends below in a small notch which is converted into a foramen, by articulation with the ethmoid
Transmits a small vein from nasal cavity to superior sagittal sinus
Crista galli
Upward continuation of perpendicular plate of ethmoid bone, to which attaches falx cerebri
Theforamen cecum, between thefrontal boneand the crista galli of the ethmoid, which usually transmits a small vein from the nasal cavity to thesuperior sagittal sinus;
Anterior Cranial Fossa
Orbital plate of the frontal bone:
It separates the anterior cranial fossa from the orbit, frontal air sinus may extend into its anteriomedial part.
Medial margins of the plate covers the lybrinth of the ethmoid and posterior margin articultaes with the lesser wing of sphenoid.
Lesser wing of sphenoid:
Is broad medially where it is continuous with the jugum spenoidale and tapers alterally.
Its free posterior borders fits into the stem of the lateral sulcus of brain.
Medially it ends as anterior clinoid process.
Inferiorly the posterior border forms the upper boundary of superior orbital fissure.
Jugum sphenoidale separates the anterior cranial fossa from the sphenoidal sinuses
Anterior cranial Fossa
It is traversed by the
frontoethmoidal suture
sphenoethmoidal suture
sphenofrontal sutures.
Anterior Cranial Fossa
Frontal lobes of brain rest on the fossa.
Traversed by frontoethmoidal, sphenoethmoidal, & sphenofrontal sutures.
The anterior clinoid process gives attachmant to the free margin of the tentorium cerebelli.
Anterior cranial Fossa
Anterior ethmoidal foramen
situated about the middle of the lateral margin of the olfactory groove,
Transmits the anterior ethmoidal vessels and the anterior ethmoidal nerve
Posterior ethmoidal foramen
Opens at the back part of this margin under cover of the projecting lamina of the sphenoid
transmits the posterior ethmoidal vessels and nerve
Fracture anterior cranial fossa