Skeletal System:- Neurocranium - 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.

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

2. Introduction of
Sphenoid Bone
Thesphenoidboneisasinglebonethatliesinthebaseoftheskull
betweenthefrontal,temporalandoccipitalbones.
Thesphenoidbonehasacentralbody,pairedgreaterandlesser
wingsthatextendlaterallyfromthebodyofthesphenoid,andtwo
pterygoidprocessesdescendingfromthejunctionofthebodyand
greaterwings.

3. Parts of
Sphenoid Bone
Themainpartsofthesphenoidboneare:
body ofsphenoid,
lesser wing ofsphenoid(2),
greater wing ofsphenoid(2),
pterygoid process (2).

4. Body of
sphenoid
Thebodyofthesphenoid(orsphenoidbody)isthecentralportion
ofthesphenoidbonelocatedbetweenthewingsandprocessesof
thesphenoid,andhousingthesphenoidalsinuses.
Thesphenoidbodyhassixsurfaces:superior,posterior,anterior,
inferior,andtwolateralsurfaces.

5. Thesuperior
surfaceof the
body of the
sphenoid It presents the following landmarks:
chiasmaticgroove,
sellaturcica with
hypophysial fossa,
tuberculum sellae,
dorsum sellae.

6. Thesuperior
surfaceof the
body of the
sphenoid
Thechiasmaticgrooveisagroovebetweentherightandleft
opticcanals.
Thesellaturcica(turkishsaddle)isasaddle-shapeddepression
onthebodyofthesphenoid,whichliesabovethesphenoidal
sinusandcontainsthehypophysis(pituitarygland).
Thehypophysialfossa(orpituitaryfossa)isadepressiononthe
superiorsurfaceofthesphenoidbodyoccupiedbythe
hypophysis.
Thetuberculumsellaeisasmallprocessinfrontofthe
hypophysialfossa.
Thedorsumsellaeistheposteriorwallofthehypophysialfossa.

7. TheLateral &
Posterior surfaceof
the body of the
sphenoid Eachlateralsurfaceuniteswiththegreaterwingandthe
pterygoidprocessofthesphenoid,andhasanimportantfeature,
thecarotidgroove.
Thecarotidgrooveisalongitudinalgroovelateraltothebodyof
thesphenoidbonethathousestheinternalcarotidartery.
Theposteriorsurfaceofthebodyofthesphenoidjoinswiththe
basilarpartoftheoccipitalbone.

8. Theanterior
surfaceof
thesphenoidbody
Theanteriorsurfaceofthesphenoidbodypresents:
openingofsphenoidalsinus(2),
septumofsphenoidalsinuses.
Theopeningofthesphenoidalsinusisanaperturethatopens
anteriorlyintothenasalcavity,specifically,intoasmallspacecalled
thespheno-ethmoidalrecess.
Thesphenoidalsinusisapairedparanasalcavitylocatedwithinthe
bodyofthesphenoid.
Theseptumofthesphenoidalsinusesisabonypartition
separatingthetwosphenoidalsinuses.

9. Theinferior
surfaceof
thesphenoidbody
Theinferiorsurfaceofthesphenoidbodypresentsinthemiddle
lineatriangularspinecalledthesphenoidalrostrum,whichfitsinto
adeepfissurebetweenthealaeofthevomer.

10. Theinternal
surfaceof the
squama of the
occipital bone
Theinternaloccipitalprotuberanceisaprominentmidpointofthe
cruciformeminence-acrossshapedbonyprominenceontheinternal
surfaceoftheoccipitalbone.
Theinternaloccipitalcrestisathickbonyridgeontheinternalsurface
oftheoccipitalbonethatoccasionallyextendsfromtheinternal
occipitalprotuberancetotheforamenmagnum.
Thegrooveforthesuperiorsagittalsinusisashallowdepressionon
thefrontal,parietal,andoccipitalbonesformingachannelforthe
sagittalsuperiorsinus;itsmarginscometogetherasitpasses
downwardandbecomecontinuouswiththefrontalcrest.
Thegrooveforthetransversesinusislocatedbilaterallyonthe
internalsurfaceoftheoccipitalboneextendingfromtheinternal
protuberancetothelateralanglesoftheoccipitalbone.

11. Theexternal
surfaceof the
squama of the
occipital bone
Theexternaloccipitalprotuberanceisapalpablebonyprojectionin
themiddleoftheoccipitalbone.
Theexternaloccipitalcrestisabonyridgeontheexternalsurfaceof
theoccipitalbonethatoccasionallyextendsfromtheexternaloccipital
protuberancetotheforamenmagnum.
Thesuperiornuchallineisatransverseridgeontheexternalsurfaceof
theoccipitalboneattheleveloftheexternaloccipitalprotuberance.It
istheattachmentsitefortheoccipitalbellyoftheoccipitofrontalis
muscle.
Theinferiornuchallineisatransverseridgeontheexternalsurfaceof
theoccipitalbonebetweenthesuperiornuchallineandtheforamen
magnum.Thesemispinaliscapitismuscleattachesbetweentheinferior
andthesuperiornuchallines.

12. Anatomical
views of the
Occipital bone

13. Dr. Aves Khan
Oral & Dental
Surgeon