The sphenoid bone is a single bone located at the base of the skull between the frontal, temporal, and occipital bones. It has a central body with greater and lesser wings extending laterally and two pterygoid processes descending from the body. The body houses the sphenoidal sinuses and has several important landmarks on its surfaces, including the sella turcica, which contains the pituitary gland. The occipital bone forms the back and base of the skull, with internal and external features like the cruciform eminence and nuchal lines for muscle attachment.

1. Sphenoid
Bone
Skeletal System
Neurocranium
Dr. Aves Khan
Oral & Dental
Surgeon

2. Introduction of
Sphenoid Bone
The sphenoid bone is a single bone that lies in the base of the skull
between the frontal, temporal and occipital bones.
The sphenoid bone has a central body, paired greater and lesser
wings that extend laterally from the body of the sphenoid, and two
pterygoid processes descending from the junction of the body and
greater wings.

3. Parts of
Sphenoid Bone
The main parts of the sphenoid bone are:
 body of sphenoid,
 lesser wing of sphenoid (2),
 greater wing of sphenoid (2),
 pterygoid process (2).

4. Body of
sphenoid
The body of the sphenoid (or sphenoid body) is the central portion
of the sphenoid bone located between the wings and processes of
the sphenoid, and housing the sphenoidal sinuses.
The sphenoid body has six surfaces: superior, posterior, anterior,
inferior, and two lateral surfaces.

5. The superior
surface of the
body of the
sphenoid It presents the following landmarks:
 chiasmatic groove,
 sella turcica with
 hypophysial fossa,
 tuberculum sellae,
 dorsum sellae.

6. The superior
surface of the
body of the
sphenoid
The chiasmatic groove is a groove between the right and left
optic canals.
The sella turcica (turkish saddle) is a saddle-shaped depression
on the body of the sphenoid, which lies above the sphenoidal
sinus and contains the hypophysis (pituitary gland).
The hypophysial fossa (or pituitary fossa) is a depression on the
superior surface of the sphenoid body occupied by the
hypophysis.
The tuberculum sellae is a small process in front of the
hypophysial fossa.
The dorsum sellae is the posterior wall of the hypophysial fossa.

7. The Lateral &
Posterior surface of
the body of the
sphenoid Each lateral surface unites with the greater wing and the
pterygoid process of the sphenoid, and has an important feature,
the carotid groove.
The carotid groove is a longitudinal groove lateral to the body of
the sphenoid bone that houses the internal carotid artery.
The posterior surface of the body of the sphenoid joins with the
basilar part of the occipital bone.

8. The anterior
surface of
the sphenoid body
The anterior surface of the sphenoid body presents:
 opening of sphenoidal sinus (2),
 septum of sphenoidal sinuses.
The opening of the sphenoidal sinus is an aperture that opens
anteriorly into the nasal cavity, specifically, into a small space called
the spheno-ethmoidal recess.
The sphenoidal sinus is a paired paranasal cavity located within the
body of the sphenoid.
The septum of the sphenoidal sinuses is a bony partition
separating the two sphenoidal sinuses.

9. The inferior
surface of
the sphenoid body
The inferior surface of the sphenoid body presents in the middle
line a triangular spine called the sphenoidal rostrum, which fits into
a deep fissure between the alae of the vomer.

10. The internal
surface of the
squama of the
occipital bone
The internal occipital protuberance is a prominent midpoint of the
cruciform eminence - a cross shaped bony prominence on the internal
surface of the occipital bone.
The internal occipital crest is a thick bony ridge on the internal surface
of the occipital bone that occasionally extends from the internal
occipital protuberance to the foramen magnum.
The groove for the superior sagittal sinus is a shallow depression on
the frontal, parietal, and occipital bones forming a channel for the
sagittal superior sinus; its margins come together as it passes
downward and become continuous with the frontal crest.
The groove for the transverse sinus is located bilaterally on the
internal surface of the occipital bone extending from the internal
protuberance to the lateral angles of the occipital bone.

11. The external
surface of the
squama of the
occipital bone
The external occipital protuberance is a palpable bony projection in
the middle of the occipital bone.
The external occipital crest is a bony ridge on the external surface of
the occipital bone that occasionally extends from the external occipital
protuberance to the foramen magnum.
The superior nuchal line is a transverse ridge on the external surface of
the occipital bone at the level of the external occipital protuberance. It
is the attachment site for the occipital belly of the occipitofrontalis
muscle.
The inferior nuchal line is a transverse ridge on the external surface of
the occipital bone between the superior nuchal line and the foramen
magnum. The semispinalis capitis muscle attaches between the inferior
and the superior nuchal lines.

12. Anatomical
views of the
Occipital bone

13. Dr. Aves Khan
Oral & Dental
Surgeon