Skeletal System 3 - Skull and Visceral Skeleton Flashcards
What does the vertebrate skull consist of
- neurocranium
- dermatocranium
- splanchnocranium
also called endocranium or primary braincase
neurocranium
lies superficial to neurocranium, has a large number of bones
dermatocranium
part of the skull that supports the jaws and is made up of bones and cartilage
splanchnocranium
- protects the brain
- begins as cartilage that is partly or entirely replaced by bone (except in cartilaginous fishes)
neurocranium or chondrocranium
how does the neurocranium begin
pair of parachordal and prechordal cartilages below the brain
exapnd and join along with notochord from basal plate
parachordal cartilage
expands and join to form an ethmoid plate
prechordal cartilages
where does the cartilage also appear
- olfactory capsule
- otic capsule
partially surrounding the olfactory epithelium
oflactory capsule
surrounds inner ear and also develops into sclera of the eyeball
otic capsule
fuses with olfactory capsules
ethmoid plate
fuses with otic capsules
basal plate
further development of cartilaginous neurocranium
- development of cartilaginous walls and
- cartilaginous roof over brain (in cartilaginous fishes)
retain a cartilaginous neurocranium (or chondrocranium) throughout life
Cartilaginous fishes
retain highly cartilaginous neurocranium that is covered by membrane bone
- Bony fishes
- lungfishes
- most ganoids
embryonic cartilaginous neurocranium is largely replaced by replacement bone
Other bony vertebrates
neurocranial ossification centers
- ethmoid center
- sphenoid center
- otic center
- occipital center
- most mammals
- nasal chamber is large & filled with ridges from the ethmoid bones -turbinals or ethmoturbinals
- these bones are covered with olfactory epithelium in life - increase the surface area for olfaction (i.e., a more acute sense of smell)
- tend to remain cartilaginous & formanterior to sphenoid
ethmoid center
ethmoid bones
- turbinals or
- ethmoturbinals
separates the nasal chamber from the brain cavity within the skull
cribiform plate
form:
- basisphenoid bone (anterior to basioccipital)
- alisphenoid
- presphenoid bone side walls above basisphenoid
sphenoid centers
anterior to basioccipital
basisphenoid bone
- bony process of the sphenoid bone in the skull, located behind each eye
- can also refer to the greater wing of the sphenoid bone.
alisphenoid
side walls above basisphenoid
presphenoid
the cartilaginous otic capsule is replaced in lower vertebrates by several bones:
- prootic
- opisthotic
- epiotic
otic centers
several bones that replaces the cartilaginous otic capsule
- prootic
- opisthotic
- epiotic
opisthotics fuse with exoccipitals
Frogs & most reptiles
- prootic, opisthotic, & epiotic unite to form a single petrosal bone;
- the petrosal, in turn, sometimes fuses with the squamosal to form the temporal bone
Birds & mammals
form a single petrosal bone
- prootic
- opisthotic
- epiotic
sometimes fuses to form the temporal bone
- petrosal
- squamosal
cartilage surrounding the foramen magnum may be replaced by as many as four bones
occipital centers