Skeletal System:- Neurocranium - Occipital bone

Anatomy of the occipital bone (latin: os occipitale), is a single bone and consists of four parts that surround the foramen magnum.

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

2. Introduction of
Occipital Bone
Theoccipitalbone(latin:osoccipitale)isasingleboneandconsistsof
fourpartsthatsurroundtheforamenmagnum.

3. Parts of
Occipital Bone
Therefourpartsformingtheoccipitalboneareasfollowing:
basilarpart,
lateralpart(2),
squamouspart.

4. Basilar part of
occipital bone
Thebasilarpartoftheoccipitalbone(alsocalledthebasioccipital)
istheportionoftheoccipitalboneextendinganteriorlyfromthe
foramenmagnumandjoiningwiththebodyofthesphenoidbone.

5. Surfaces of
The basilar
part of the
occipital bone
Theinternalsurfaceofthebasioccipitalfeaturesthefollowing
structures:
clivus,
grooveforinferiorpetrosalsinus(2).
Theclivusisaslopingmedialsurfaceofthebasalpartof
theoccipitalbonebehindthedorsumsellae,slopingdownwardto
theforamenmagnum.Theclivusisoccupiedbythemedulla
oblongataandpons.
Thegrooveforinferiorpetrosalsinusisformedbythejunctionof
thepetrouspartofthetemporalbonewiththebasilarpartof
theoccipitalbone.

6. Surfaces of
The basilar
part of the
occipital bone
Theexternalsurfaceofthebasioccipitalfeaturesthepharyngeal
tubercle.
Thepharyngealtubercle(orpharyngealeminence)isa
prominenceontheinferiorsurfaceoftheoccipitalbone,
specifically,ontheoutersurfaceofthebasilarpartoftheoccipital
bone,forattachmentofthepharyngealraphe.

7. Lateral part of
occipital bone
Eachlateralpartoftheoccipitalbonehasaninternalandan
externalsurface.
Theinternalsurfaceofthelateralpartoftheoccipital
bonepresentsthegrooveforthesigmoidsinus.
Thegrooveforthesigmoidsinusislocatedintheposterior
cranialfossa,foundonthelateralpartoftheoccipitalbone,then
curvingaroundthejugularprocessonthemastoidpartofthe
temporalbone,finally,turningsharplyontheinnersurfaceofthe
parietalbone,continuingasthetransversegroove.

8. The external
surface of the
lateral part of
theoccipital
bone
Itfeaturesthefollowingstructures:
occipitalcondyle,
condylarcanal,
hypoglossalcanal.
Theoccipitalcondyleisaprocessontheoccipitalboneforarticulation
withtheatlas.
Thecondylarcanalisabonypassagelocatedinthelateralpartof
theoccipitalboneposteriortotheoccipitalcondyletransmittingavein
fromthesigmoidsinus.
Thehypoglossalcanalisabonypassagethatoriginatesfromthe
lateralpartoftheoccipitalboneanteriortotheforamenmagnumand
endsontheoutersurfaceanteriortotheoccipitalcondyle.The
hypoglossalcanaltransmitsthehypoglossalnerve(CNXII)andavenous
plexus.

9. Squamous
part of
occipital bone
Thesquamouspart(alsocalledsquamaofoccipitalbone,occipital
squama)oftheoccipitalbonehasaninternalandanexternalsurface.
Theinternalsurfaceofthesquamaoftheoccipitalbonefeatures:
internaloccipitalprotuberance,
internaloccipitalcrest,
grooveforsuperiorsagittalsinus,
groovefortransversesinus(2).
Theexternalsurfaceofthesquamaoftheoccipitalbonefeatures:
externaloccipitalprotuberance,
externaloccipitalcrest,
superiornuchalline,
inferiornuchalline.

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