axial skeleton - skull neurocranium dermatocranium splanchnocranium
TRANSCRIPT
Axial Skeleton - Skull
NeurocraniumDermatocraniumSplanchnocranium
Dermatocranium
Phylogeny – membrane bone which evolved from dermal armor
Roofing bonesAlong side and above brain
Roofing Bones
NasalFrontalParietalOrbital
– Lacrimal– Jugal = Infraorbital = Zygomatic
Squamosal
Look at the Skull & Lower Jaw components page. Examine the roofing bones.
Upper jaw
PremaxillaMaxilla
Lower Jaw
Dentary - largestSplenial – small, dorsomedialSurangular - lateralAngular – medial, becomes typanic bullaCoronoid – medial Prearticular – medial & caudal – becomes
anterior malleus in mammals
Key Points
Look at upper and lower jaw dermatocranium bones on Skull & Lower Jaw Components page
Give an example of homology.What trend do you see in lower jaw
evolution?
Primary Palate Bones
Roof of oropharyngeal cavity in fish, amphibians
Roof of nasal cavity in amniotes
Primary Palate
VomerPalatinePterygoid
Primary Palate
Examine Skull & Lower Jaw Components page
Dermatocranium
Operculum
Key Point
Describe dermatocranium bones in the shark…
Axial Skeleton - Skull
NeurocraniumDermatocraniumSplanchnocranium – Visceral skeleton
Splanchnocranium
Supports & allows movement of jaws, gill, tongue
Associated with hearingAncient in evolutionReplacement bone
Splanchnocranium
Typically 6 gill slits between Visceral arches A typical visceral arch that is gill in function has
five segments– Pharyngobranchial– Epibranchial– Ceratobranchial– Hypobranchial– Basibranchial
Splanchnocranium
Mandibular arch = Visceral Arch IPalatoquadrateMandibular = Meckel’s Cartilage
Splanchnocranium
Hyoid arch = Visceral arch IIHyomandibulaCeratohyalBasihyal
Interrelationships
The neurocranium, dermatocranium and splanchnocranium eventually becomes intimately associated to form one single, firm skull
Key Point Describe the origin of jaws from
this picture
Key Point
The three main components of the cranium are: