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: