Anatomy Of The Vertebrate Skull
Comparative Vertebrate Anatomy
Lecture Notes - Skeletal System II (Skull)
The Vertebrate Skull consists of: 1 - neurocranium (also called endocranium or primary braincase) 2 - dermatocranium (membrane bones) 3 - splanchnocranium (or visceral skeleton) Neurocranium:
1 - protects the brain
2 - begins as cartilage that is partly or entirely replaced by bone (except in cartilaginous fishes) Cartilaginous stage: neurocranium begins as pair of parachordal & prechordal cartilages below the brain parachordal cartilages expand & join; along with the notochord from the basal plate prechordal cartilages expand & join to form an ethmoid plate
Cartilage also appears in the olfactory capsule (partially surrounding the olfactory epithelium) otic capsule (surrounds inner ear & also develops into sclera of the eyeball)
Completion of floor, walls, & roof:
Ethmoid plate - fuses with olfactory capsules
Basal plate - fuses with otic capsules
Further development of cartilaginous neurocranium = development of cartilaginous walls (sides of braincase) &, in cartilaginous fishes, a cartilaginous roof over the brain
Cartilaginous fishes - retain a cartilaginous neurocranium (or chondrocranium) throughout life
Bony fishes, lungfishes, & most ganoids - retain highly cartilaginous neurocranium that is covered by membrane bone
Cyclostomes - the several cartilaginous components of the embryonic neurocranium remain in adults as more or less independent cartilages Source: http://gwis2.circ.gwu.edu/~atkins/newwebpages/Skeletal/Skeletable.html
Other bony vertebrates - embryonic cartilaginous neurocranium is largely replaced by replacement bone (the process of endochondral ossification occurs almost simultaneously at several ossification centers) Neurocranial ossification centers:
1 - occipital centers cartilage surrounding the foramen magnum may be replaced by as many as four bones: basioccipital exoccipital (2) supraoccipital Mammals - all 4 occipital elements typically
Lecture Notes - Skeletal System II (Skull)
The Vertebrate Skull consists of: 1 - neurocranium (also called endocranium or primary braincase) 2 - dermatocranium (membrane bones) 3 - splanchnocranium (or visceral skeleton) Neurocranium:
1 - protects the brain
2 - begins as cartilage that is partly or entirely replaced by bone (except in cartilaginous fishes) Cartilaginous stage: neurocranium begins as pair of parachordal & prechordal cartilages below the brain parachordal cartilages expand & join; along with the notochord from the basal plate prechordal cartilages expand & join to form an ethmoid plate
Cartilage also appears in the olfactory capsule (partially surrounding the olfactory epithelium) otic capsule (surrounds inner ear & also develops into sclera of the eyeball)
Completion of floor, walls, & roof:
Ethmoid plate - fuses with olfactory capsules
Basal plate - fuses with otic capsules
Further development of cartilaginous neurocranium = development of cartilaginous walls (sides of braincase) &, in cartilaginous fishes, a cartilaginous roof over the brain
Cartilaginous fishes - retain a cartilaginous neurocranium (or chondrocranium) throughout life
Bony fishes, lungfishes, & most ganoids - retain highly cartilaginous neurocranium that is covered by membrane bone
Cyclostomes - the several cartilaginous components of the embryonic neurocranium remain in adults as more or less independent cartilages Source: http://gwis2.circ.gwu.edu/~atkins/newwebpages/Skeletal/Skeletable.html
Other bony vertebrates - embryonic cartilaginous neurocranium is largely replaced by replacement bone (the process of endochondral ossification occurs almost simultaneously at several ossification centers) Neurocranial ossification centers:
1 - occipital centers cartilage surrounding the foramen magnum may be replaced by as many as four bones: basioccipital exoccipital (2) supraoccipital Mammals - all 4 occipital elements typically