Base of skull

Skull base
File:Skull interior anatomy.svg Base of the skull, inferior or inner surface
File:Skull base anatomy.jpg Base of the skull, exterior or outer surface. Showing various muscle attachments.
Details
Identifiers
Latin	basis cranii externa et. interna
TA98
TH	{{#property:P1694}}
TE	{{#property:P1693}}
FMA	{{#property:P1402}}
Anatomical terms of bone

The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the calvaria.

Structure

File:Gray187.png

Base of the skull. Inferior surface, attachment of muscles marked in red.

Structures found at the base of the skull are for example:

Bones

There are five bones that make up the base of the skull:

• Ethmoid bone
• Sphenoid bone
• Occipital bone
• Frontal bone
• Temporal bone

File:Exobasis.jpg

Exobasis

Sinuses

• Occipital sinus
• Superior sagittal sinus
• Superior petrosal sinus

Foramina of the skull

Main article: Foramina of the skull

• Foramen cecum
• Optic foramen
• Foramen lacerum
• Foramen rotundum
• Foramen magnum
• Foramen ovale
• Jugular foramen
• Internal auditory meatus
• Mastoid foramen
• Sphenoidal emissary foramen
• Foramen spinosum

File:Endobasis - resistances beams.jpg

Endobasis-resistances beams

File:Endobasis - resistances nodes.jpg

Endobasis-resistances nodes

Sutures

• Frontoethmoidal suture
• Sphenofrontal suture
• Sphenopetrosal suture
• Sphenoethmoidal suture
• Petrosquamous suture
• Sphenosquamosal suture

Other

File:Skull brain human normal.svg

The foramina in the base of the skull are exit and entry points for veins, arteries and cranial nerves.

File:Skull and brainstem inner ear.svg

The cranial nerves as they exit through various foramina.

• Sphenoidal lingula
• Subarcuate fossa
• Dorsum sellae
• Jugular process
• Petro-occipital fissure
• Condylar canal
• Jugular tubercle
• Tuberculum sellae
• Carotid groove
• Fossa hypophyseos
• Posterior clinoid processes
• Sigmoid sulcus
• Internal occipital protuberance
• Internal occipital crest
• Ethmoidal spine
• Vestibular aqueduct
• Chiasmatic groove
• Middle clinoid process
• Groove for sigmoid sinus
• Trigeminal ganglion
• Middle cranial fossa
• Anterior cranial fossa
• Middle meningeal artery
• Cribriform plate
• Posterior cranial fossa
• Nasociliary nerve
• Hypoglossal canal

Development

During the fetal period, the geometry of the cranial base and its fossae: anterior, middle and posterior undergoes rapid changes. The anterior part of the cranial base undergoes changes rapidly particularly in the first trimester, and cranial defects can frequently develop during this period. Growth of the anterior part of cranial base is uneven during the prenatal period. Allometric growth is observed in the first trimester, with the longitudinal dimension increasing from 5 to 17 millimeters between the 8th and 14th weeks of fetal life. Simultaneously, the angle of the anterior cranial fossa decreases, and its depth increases toward the middle fossa. In the second trimester, growth continues but becomes more uniform, and changes in the angle of the anterior fossa are minor. The angle between the lesser wings of the sphenoid bone gradually decreases with increasing depth of the anterior fossa in the frontal plane.

Additional images

• Base of the skull. Upper surface
  Base of the skull. Upper surface
• Base of skull
  Base of skull
• Base of skull - crista galli, cribriform plate and foramen cecum
  Base of skull - crista galli, cribriform plate and foramen cecum
• Base of skull - sella turcica
  Base of skull - sella turcica
• The anterior, middle and posterior cranial fossa in different colors
  The anterior, middle and posterior cranial fossa in different colors