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Skull and Visceral Skeleton Skull: Neurocranium Dermatocranium Splanchnocranium: Palatoquadrate cartilage and replacement bone Meckel’s cartilage and replacement.

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Presentation on theme: "Skull and Visceral Skeleton Skull: Neurocranium Dermatocranium Splanchnocranium: Palatoquadrate cartilage and replacement bone Meckel’s cartilage and replacement."— Presentation transcript:

1 Skull and Visceral Skeleton Skull: Neurocranium Dermatocranium Splanchnocranium: Palatoquadrate cartilage and replacement bone Meckel’s cartilage and replacement bone Skeleton of the branchial arches

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3 Neurocranium Primary braincase protects brain arises as cartilage, which... is replaced by bone similar development in all vertebrates

4 Formation Paired prechordal (neural crest) and parachordal (lat. plate mesoderm) cartilage. Also cartilage around olfactory, otic and, sometimes, optic capsules

5 Parachordal cartilage unites to form basal plate and joins otic capsules Prechordal cartilage unites to form ethmoid plate and joins olfactory (and optic) capsules

6 Further development involves: formation of walls a cartilaginous tectum (lower vertebrates) fenestra and foramina for passage of blood vessels

7 Cartilaginous Neurocrania in Adult Vertebrates Cyclostomes: individual components more or less independent throughout life Cartilaginous fish: union of components to enclose brain forming the chondrocranium Lower bony fish: cartilaginous neurocranium persists; overlain with dermal bone (chondrosteans and holosteans)

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9 Ossification Centers in Neurocranium Occipital: 4 areas around the foramen magnum Sphenoid: under midbrain and pituitary - forms sphenoid Ethmoid: ethmoid plate and olfactory capsules. Tends to remain cartilaginous in adults as cribiform plate. Otic: several bones form (prootics, opisthotic, epiotics form petrosal). Petrosal fuses with squamosal to form the temporal bone

10 Dermatocranium Membrane bones of the skull which may have originated in bony dermal armor of the ostracoderms In modern vertebrates, formation from subdermal mesenchyme of neural crest and lateral plate mesoderm rather than dermal mesenchyme Basic structural elements: roofing bones of the neurocranium, marginal bones of upper jaw, bones of primary palate and opercular bones

11 Roofing bones: nasal (N), frontal (F), parietals (P) and dermooccipitals (DO)

12 Orbit of eye: lacrimal (lac), prefrontal (PF), postfrontal (PoF), postorbital (PO) and jugal.

13 Posterior angle of skull: intertemporal (IT), supratemporal (ST), tabular (Tab), squamosal (Sq) and quadrojugal (Qj)

14 Marginal bones of upper jaw: premaxillae (Pre) and maxilla

15 Primary palatal bones: volmer (1), palatines (2), ectopterygoid (3), pterygoid (4) and parasphenoid (5)


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