Axial Skeleton Skull Cephalization Neurocranium – Protects brain & sensory structures –...

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Axial Skeleton Skull Cephalization Neurocranium Protects brain & sensory structures Phylogeny – common to all vertebrates Replacement bone

Transcript of Axial Skeleton Skull Cephalization Neurocranium – Protects brain & sensory structures –...

Axial Skeleton

SkullCephalizationNeurocranium

– Protects brain & sensory structures– Phylogeny – common to all vertebrates– Replacement bone

Chondrocranium development

Prechordal cartilage (trabeculae cranii) form

Underneath brainAnterior to notochord

Prechordal cartilage

Form under forebrain regionForm nasal = olfactory capsulesForm optic capsules in orbitForm rostrumFinally expands to become ethmoid plate

Parachordal cartilage

Forms beside and posterior to notochordForms floor of hindbrainExpands to form basal plateForms occipital condyles (1-2) and foramen

magnum

Sensory capsules

As floor of cranium forms, so do sensory capsules

Olfactory capsuleOtic capsule for inner ear structuresOptic capsule (not attached – outer covering

of eyeball)

Plate expansion

Ethmoid plate expands and unites with olfactory capsule

Basal plate expands and unites with otic capsule

Formina remain for nerves & blood vesselsHypophyseal fenestra remains for pituitary

gland

Question

Singular of foramina?Fenestra?

Ossification Centers

Ethmoid plate, basal plate & sensory capsules ossify

Four ossification centersOccipital (back), Otic (ear), Sphenoid

(floor), Ethmoid (floor)

Occipital Ossification Center

Foramen magnumBasioccipitalExoccipitalSupraoccipitalOccipital Condyles

Otic ossification center

Sphenoid ossification center

BasisphenoidPresphenoid/Sphenethmoid

Ethmoid ossification center

Ethmoid plateOlfactory capsulesTurbinates in mammals

Neurocranium

Look at Skull & Lower Jaw Components page

Key Points

What is one important trend of the NEUROCRANIUM from the Skull & Lower Jaw Components page?