Module 2- Parachordal Cartilage & Mesethmoid

earliest cartilage to form

-parachordal cartilage

-Sox9 → cartilage

parts of chondrocranium

-prechordal: anterior to notochord

-chordal: surrounding notochord

-boundary between prechordal and chordal is just posterior to the sella turcica

possible fates of chondrocranium

-chondrocranium forms at 7 weeks

-endochondral replacement

-persistent as permanent cartilage

-resorption without replacement

endochondral remodeling v non-endochondral remodeling

nasal capsule (ectethmoid)

-ethmoid (trabeculae cranium + nasal capsule) and inferior concha form ENTIRELY by endochondral ossification

-nasal capsule → endo ossif → ectemoid (lateral component of ethmoid bone)

-lateral labyrinths, superior/middle conchae, inferior concha (inferior concha still attached and this is lost during end ossification)

ectethmoid also gives rise to

-cribriform plate and lateral nasal cartilages

trabeculae cranii (mesethmoid)

-form nasal septal cartilage, perpendicular plate of ethmoid, crista galli of ethmoid

vomer

-forms as 2 separate bones on either side of base of trabeculae crania

-between those 2 plates, can find cartilagenous remnants that can become a tumor