COMPARATIVE VERTEBRATE ANATOMY (SKULL) Flashcards
The vertebrate skull consist of:
neurocranium
dermatocranium
splanchnocranium
also called endocranium or primary braincase
neurocranium
membrane bones
dermatocranium
visceral skeleton
splanchnocranium
protects the brain
neurocranium
begins as cartilage that is partly or entirely replaced by bone
neurocranium
neurocranium begins as pair of parachordal & prechordal cartilages below the brain
cartilaginous stage
parachordal cartilages expand and join; along with the notochord from the basal plate
cartilaginous stage
prechordal cartilages expand & join to form an ethmoid plate
cartilaginous stage
where does cartilage appear?
olfactory capsule
otic capsule
partially surrounding the olfactory epithelium
olfactory capsule
surrounds inner ear & also develops into sclera of the eyeball
otic capsule
In the completion of floor, walls, and roof, it fuses with olfactory capsules
ethmoid plate
In the completion of floor, walls, and roof, it fuses with otic capsules
basal plate
further development of neurocranium means
development of cartilaginous walls (sides of braincase);
in cartilaginous fishes, cartilaginous roof over the brain
retain a cartilaginous neurocranium (or chondrocranium) throughout life
cartilaginous fishes
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
Other bony vertebrates
embryonic cartilaginous neurocranium is largely replaced by replacement bone
(the process of endochondral ossification occurs almost simultaneously at several ossification centers)
what are the neurocranial ossification centers?
occipital centers
sphenoid centers
ethmoid centers
otic centers
cartilage surrounding the foramen magnum may
be replaced by as many as four bones:
basioccipital
exoccipital (2)
supraoccipital
all 4 occipital elements typically fuse
to form a single occipital bone
mammals
neurocranium articulates with the 1st vertebra via 1 (reptiles and birds) or 2
(amphibians and mammals) occipital condyles
tetrapods
what does the sphenoid center form?
basisphenoid
presphenoid
side walls of basisphenoid and presphenoid
side walls of basisphenoid and presphenoid
orbitosphenoid
pleurosphenoid
alisphenoid
what center tends to remain cartilaginous
ethmoid center
what does the ethmoid center form?
anterior to sphenoid
cribiform plate of ethmoid & several conchae (or ethmoturbinal bones)
nasal chamber is large & filled with ridges from the ethmoid bones called the turbinals or ethmoturbinals.
mammals
ridges from the ethmoid bones
turbinals or ethmoturbinals
are covered with olfactory epithelium in life and serve to increase the surface area for
olfaction (i.e., a more acute sense of smell).
ethmoid bones
separates the nasal chamber from the brain cavity
within the skull.
cribriform plate
the center wherein cartilaginous otic capsule is replaced in lower vertebrates by several bones
otic centers
What are the bones that replace cartilaginous capsule in lower vertebrates?
prootic
opisthotic
epiotic
(one or more of these bones may unite with adjacent replacement or membrane bones)
opisthotics fuse with exoccipitals
frogs and 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 and mammals
What is formed when prootic, opisthotic, and epiotic unite?
single petrosal bone
What is formed when petrosal bone is fused with squamosal bone?
temporal bone
What lies superficial to neurocranium
dermatocranium
What forms:
1 - bones that form the roof of the brain & contribute to the lateral walls of the skull
2 - bones of the upper jaw
3 - bones of the palate(s)
4 - opercular bones
dermatocranium
What does the dermatocranium forms?
1 - bones that form the roof of the brain & contribute to the lateral walls of the skull
2 - bones of the upper jaw
3 - bones of the palate(s)
4 - opercular bones
What are the basic pattern of roofing bones?
crossopterygians
labyrinthodonts
Fontanels
a series of paired & unpaired bones along mid-dorsal line of skull (below left)
crossopterygians
unpaired bones lost & a series of paired bones resulted (nasals, frontals,
parietals, & dermoccipitals) (below right)
labyrinthodonts
‘soft spots’
fontanels
occur when neurocranium is incomplete dorsally (e.g., teleosts & tetrapods)
fontanels
can be felt in head until the membranes under the skin have ossified
fontanels
What are the bones of the upper jaw?
Pterygoquadrate (palatoquadrate) cartilage
Palatal bones
1st upper jaw that vertebrate embryos develop
Pterygoquadrate (palatoquadrate) cartilage
What only has palatoquadrate as the only upper jaw that develops?
Cartilaginous fishes
what has their palatoquadrate becomes covered with dermal bones (premaxillae &
maxillae) that make up the adult upper jaw?
bony vertebrates
what are the dermal bones?
premaxillae and maxillae
the floor on which the brain rests is at the same time the roof of the oral cavity in fishes
& amphibians (primary palate)
palatal bones
What type of palatal bones is present in sharks?
cartilaginous
What type of palatal bones is present in bony vertebrate?
membrane bones
a secondary (‘false’) palate develops creating a horizontal
partition that separates the oral cavity into nasal & oral passages.
Birds, mammals, & some reptiles
formed from processes of the premaxillae, maxillae, and palatines
secondary palate
consist of operculum
Opercular bones
fold of the hyoid arch that extends back over the gill slits in holocephalans & bony
fishes
operculum
no vestiges of opercular bones remain
tetrapods
