A2 - Bones of the lateral and dorsal side of the neurocranium

Question 1

Which bones are the lateral wall of neurocranium composed of? And name the relevant structures

Answer 1

Os temporale are the lateral wall of neurocranium

Pars squamosa

• Proc. zygomaticus
• Proc. retroarticularis (attachemnt for ligaments)
• Proc. occipitale (form suture with os. occipitale, behind proc zygomaticus)
• Proc. retrotympanicus (surround auditory meatus)
• Proc. nuchalis???? (extra attachment for os hyoideum in sus)
• For. retroarticulare (→ meatus temporalis → canalis temporalis (ø sus, fe))

Pars petrosa

• Encloses the inner and middle ear, bordered by pars temporalis and pars squamous
• External:
  
  • Proc. mastoideus (ø sus) (connects os hyoideum in ca)
  • Proc. styloideus (connects hyoid in eq, ru)
  • For. stylomastoideum (→ canalis facialis)
• Internal:
  
  • Porus acusticus internus (opening of meatus acusticus internus)
    
    • → n. facialis
    • → n. vestibulocochlearis
  • Impressio n. trigemini (ø ca)
  • Canalis n. trigemini (ca) (ggl. trigeminale)
  • Crista partis petrosae (eq, ca) (division rostral and medial suface of os petrosa
  • Area cochela (n. vestebulotrochlearis )
  • Fossa cerebellaris (dorsal to meatus acusticus internus)

Pars tympanica

• Base of os temporale
• Tympanic cavity
• External:
  
  • Bulla tympanica (
    
    • Septum bullae
  • Proc. muscularis (large in eq, ru)
  • Porus acusticus externus (opening for osseus external acustical meatus)
  • Fissura petrotympanica (passage for chorda tympanica)
• Internal:
  
  • Canalis caroticus (Medial wall of bulla tympanica, Ca: A. carotis interna)
  • Canalis musculotubaris (→ tympanic cavity for tuba auditiva and m. tensor veli palatini)
    
    • ​Semicanalis tubae auditivae
    • Semicanalis musculi tensor veli palatini

Question 2

Which bones are the dorsal side of neurocranium composed of? And name the relevant structures

Answer 2

• Superior portions of:
  
  • Os frontale
  • Os parietale, interparietale
  • (Os occipitale)
• Calvaria: roof of cranium
  
  • Lamina externa
  • Diploë (spongiosa between lamina externa and lamina interna)
  • Lamina interna
• Proc. tentorius → (of os occipitale, os interparietale, ossa parietalia)
  
  • ​Tentorium cerebellaris osseum (ca, eq)
  • Eminentia crusiforums (ru, sus)

Os parietale

• Paired
• Internal:
  
  • Christa saggitalis interna
  • Proc. tentoricus
• External:
  
  • Linea temporalis
  • Christa saggitalis externa (eq, ca)

Os interparietalis

• Proc. tentoricus
• Caud. part of christa saggitalis externa/interna

Os frontale

• Paired
• Squamous frontalis
  
  • ​Margo supraorbitale
  • Proc. cornualis (ru)
  • For. supraorbitalis (eq, ru)
• Facies temporalis
  
  • ​Linea temporalis
  • Christa orbitemporalis
  • Proc. zygomaticus
    
    • ​Ru: +proc frontalis
    • Eq: +proc. zygomaticus (temproal)
    • Ca: Lig. orbitalis ????
  • Crista frontalis
• Pars orbitalis (medial wall of orbit)
  
  • For. ethmoidale (eq: opens on the border between os frontale and os sphenoidale
  • Fossa glandulae lacrimalis (ru, eq: for gl. lacrimalis)
  • Facies temporalis
  • Fossa temporalis (muscle attachment)
  • Fovea trochlearis ( for m. obliquus dorsalis)
  • For. ethmoidale
  • Forr. ethmoidalia (ca)
  • Christa orbitalis ventralis
• Internal roof:
  
  • Impressio digitae (gyri of brain)
  • Impressio vermails (impressio from vermis cerebelli)
  • Tentorium cerebelli osseum (separate cerebrum and cerebellum)
  • Christa saggitlais interna (→ christa galli)