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1. Axial Skeleton Skull
Cephalization
Neurocranium
Protects brain & sensory structures
Phylogeny – common to all vertebrates
Replacement bone
2. Chondrocranium development
Prechordal cartilage (trabeculae cranii) form
Underneath brain
Anterior to notochord
4. Prechordal cartilage Form under forebrain region
Form nasal = olfactory capsules
Form optic capsules in orbit
Form rostrum
Finally expands to become ethmoid plate
8. Parachordal cartilage Forms beside and posterior to notochord
Forms floor of hindbrain
Expands to form basal plate
Forms occipital condyles (1-2) and foramen magnum
11. Sensory capsules As floor of cranium forms, so do sensory capsules
Olfactory capsule
Otic capsule for inner ear structures
Optic capsule (not attached – outer covering of eyeball)
14. Plate expansion Ethmoid plate expands and unites with olfactory capsule
Basal plate expands and unites with otic capsule
Formina remain for nerves & blood vessels
Hypophyseal fenestra remains for pituitary gland
15. Question Singular of foramina?
Fenestra?
16. Ossification Centers Ethmoid plate, basal plate & sensory capsules ossify
Four ossification centers
Occipital (back), Otic (ear), Sphenoid (floor), Ethmoid (floor)
18. Occipital Ossification Center Foramen magnum
Basioccipital
Exoccipital
Supraoccipital
Occipital Condyles
22. Otic ossification center
23. Sphenoid ossification center Basisphenoid
Presphenoid/Sphenethmoid
26. Ethmoid ossification center Ethmoid plate
Olfactory capsules
Turbinates in mammals
31. Neurocranium Look at Skull & Lower Jaw Components page
32. Key Points What is one important trend of the NEUROCRANIUM from the Skull & Lower Jaw Components page?