The Sphenoid Bone
The sphenoid bone is one of the eight bones that make up the cranium – the superior
aspect of the skull that encloses and protects the brain.
Its name is derived from the Greek ‘sphenoeides’, to mean wedge-shaped.
In this article, we shall look at the anatomy of the sphenoid bone – its location,
structure, and clinical significance.
Fig 1 – The position of the sphenoid bone (yellow) within the facial skeleton.
Anatomical Structure
The sphenoid bone is said to be ‘butterfly-shaped‘. It consists of a body, paired
greater wings and lesser wings, and two pterygoid processes.
Body
The body lies at the centre of the sphenoid bone, and is almost completely cubical in
shape.
It contains the sphenoidal sinuses, which are separated by a septum – meaning that
the sphenoid body is essentially hollow. The body articulates with the ethmoid bone
anteriorly, and it is here that the sinuses open up into the nasal cavity.
The superior surface of the sphenoid body contains some important bony landmarks:
Sella turcica – a saddle-shaped depression. It has three parts:
Tuberculum sellae – forms the anterior wall of the sella turcica, and the posterior
aspect of the chiasmatic groove.
, Hypophyseal fossa – the deepest part of the sella turcica, where the pituitary gland
is located.
Dorsum sellae – forms the posterior wall of the sella turcica.
Chiasmatic groove – a sulcus formed by the optic chiasm (where the optic nerves
partially cross).
The sella turcica is surrounded by the anterior and posterior clinoid processes. The
anterior clinoid processes arise from the sphenoidal lesser wings, while the posterior
clinoid processes are the superolateral projections of the dorsum sellae. They serve
as attachment points for the tentorium cerebelli, a membranous sheet that divides
the brain.
© B y Teac hMeS eries L td (2021)
F ig 2 – F oramina and bony landmark s of the s phenoid wing s and pteryg oid proc es s .
The sphenoid bone is one of the eight bones that make up the cranium – the superior
aspect of the skull that encloses and protects the brain.
Its name is derived from the Greek ‘sphenoeides’, to mean wedge-shaped.
In this article, we shall look at the anatomy of the sphenoid bone – its location,
structure, and clinical significance.
Fig 1 – The position of the sphenoid bone (yellow) within the facial skeleton.
Anatomical Structure
The sphenoid bone is said to be ‘butterfly-shaped‘. It consists of a body, paired
greater wings and lesser wings, and two pterygoid processes.
Body
The body lies at the centre of the sphenoid bone, and is almost completely cubical in
shape.
It contains the sphenoidal sinuses, which are separated by a septum – meaning that
the sphenoid body is essentially hollow. The body articulates with the ethmoid bone
anteriorly, and it is here that the sinuses open up into the nasal cavity.
The superior surface of the sphenoid body contains some important bony landmarks:
Sella turcica – a saddle-shaped depression. It has three parts:
Tuberculum sellae – forms the anterior wall of the sella turcica, and the posterior
aspect of the chiasmatic groove.
, Hypophyseal fossa – the deepest part of the sella turcica, where the pituitary gland
is located.
Dorsum sellae – forms the posterior wall of the sella turcica.
Chiasmatic groove – a sulcus formed by the optic chiasm (where the optic nerves
partially cross).
The sella turcica is surrounded by the anterior and posterior clinoid processes. The
anterior clinoid processes arise from the sphenoidal lesser wings, while the posterior
clinoid processes are the superolateral projections of the dorsum sellae. They serve
as attachment points for the tentorium cerebelli, a membranous sheet that divides
the brain.
© B y Teac hMeS eries L td (2021)
F ig 2 – F oramina and bony landmark s of the s phenoid wing s and pteryg oid proc es s .
