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?