CRANIAL FOSSAE
The internal surface of the neurocranium base has 3 depressions which create the bowl shape of the cranial cavity that accommodate the brain. Figure 1 displays the 3 depressions/fossae. The fossae increase in depth from anterior to posterior and are termed the:
- Anterior cranial fossa
- Middle cranial fossa
- Posterior cranial fossa
ANTERIOR CRANIAL FOSSA
The anterior fossa is formed from the frontal bone anteriorly, the ethmoid bone in the midline and the body and the lesser wings of the sphenoid bone posteriorly (Figure 2). Two skull foramina located in the anterior fossa:
- Foramen caecum
- Foramen of the cribriform plate
Middle cranial fossa
The middle cranial fossa is butterfly shaped and is located posteroinferior to the anterior fossa (Figure 3). Both the greater wings of the sphenoid and temporal bone create the lateral sections of the fossa. The middle cranial fossa contains 6 foramina:
- Optic canal
- Superior orbital fissure
- Foramen rotundum
- Foramen ovale
- Foramen spinosum
- Foramen lacerum
Posterior Cranial Fossa
The posterior fossa is the largest and deepest of the 3 fossae. The occipital bone is the main contributor to the fossa and the temporal bone forms the antero-lateral boundaries (Figure 4). There are 4 foramina found in the posterior cranial fossa:
- Internal acoustic meatus
- Jugular foramen
- Hypoglossal canal
- Foramen magnum
POP QUIZ
Check how much of the cranial fossae section you understand by completing the quiz below.
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