A1 - Bones of the base of neurocranium

Question 1

Define neurocranium

Answer 1

Holds the brain and contains cranial cavity

Question 2

Name the bones of the base of neurocranium

Answer 2

• Os sphenoidale
  
  • ​Preshenidale
  • Basis sphenoidale
• Os occipitale, pars basalis

Question 3

Give the division of the base of the neurocranium

Answer 3

• Fossa cranii rostralis
  
  • ​Between laminae cribosa → alae ossis presphenoidalis
• Fossa cranii media
  
  • ​From the caudal borders of the alae ossis presphenoidalis → crista sphenooccipitalis and crista partis petrosae
• Fossa cranii caudalis
  
  • ​From crisa sphenooccipitalis and cristae partis petrosae → for. magnum

Question 4

Structures of the base of neurocranium

Answer 4

Fossa cranii rostralis:

• ​Formed by corpus ossis prespheniodalis and ala orbitalis (wing of spenoid bone)
• Opens rostrally into nasal cavity
• Sulcus chiasmatis in the caudal part of presphenoid
  
  • Opens to right/left optic channels
  • Canalis opticus → orbit

Fossa cranii media:

• ​Depression on the basis sphenoid
• Extends caudally to crista spenooccipitalis
• In the middle of the middle fossa, the basisphenoid forms sella turica → fossa hypophysalsis
• On either side the ala temporalis forms grooves: 2-3, on the medial-dorsal surface of the wings
  
  • The caudal border ends in incisurae, opens into foramen lacerum
    
    • ​Medial: Sulcus caroticus→ inc. carotica
    • Middle: Sulcus n. opthalmichi → inc. ovalis
    • Lateral: Sulcus n. maxillaris → inc. spinosa
  • Fossa piriformis foud lateral of sulcus nervi maxillaris → spina ossis sphenoidale separate the fossa and sulcus

Fossa cranii caudalis:

• Os occipitalis, pars basilaris
• Leads caudally to for. magnum
• The meidan region of pars basilaris is divided in two:
  
  • Rostrally: Impressio pontina
  • Caudally: Impressio medullaris
• For. jugulare
  
  • ​Lateral to impressio medullaris
  • Eq, Sus: Incisura at the caudal end of for. lacerum
  • Ca, ru: separate foramen

Question 5

Interspecies, foramen

Answer 5

Question 6

Basis cranii interna

Answer 6

Fossa cranii rostralis

• Corpus + ala presphenoidale
• Lamina criboforma → crista orbisphenoidale
• Sulcus chiasmatis
  
  • Chiasma opticum → Canalis oprticum (ala prespeniodale) → For. opticum

Fossa cranii media

• Crista orbisphenoidale
  
  • Crista sphenoidale
• Sella turica (rostral)
• Fossa hypophysialis
• Dorsum sellae turica (caudal) (Eq)
• Ala basisphenoidale
• Sulcus n. opthalmichi → fissura orbitalis → inc. ovalis
• Sulcus n. maxillaris → for. alare rostrale / for. rotundum → inc. spinosa
• Sulcus carotica
  
  • Ca: For. caroticum
  • Eq: Inc. caroticum
  • Eq, sus: opens into for. lacerum
• Fossa piriformis (for the piriform lobe)
  
  • Lateral to the most lateral groove (sulcus n. maxillaris)

Fossa cranii caudalis

• Os occipitale
• Crista sphenooccipitale
  
  • For magnum
• Impressio pontina
• Impressio medullaris