The Skull And Appendicular Skeleton Flashcards
what is the splanchnocranium?
bones etc of the throat and lower mouth
arose to support pharyngeal slits in protochordates
what is the chondrocranium?
cartilage of the skull
supports the brain
what is the dermatocranium?
cells that form the dermis
‘outer casing’ and dermal bones of skull
what is dermal bone formation?
‘intramembranous’ ie from mesenchyme via osteoclasts etc
osteoblast deposition superficially
eg: jaw, gills, scapula, most flat bones
what is endochondral bone formation?
cartilage (chondrocranium) replaced by bone
eg: most of the postcranial internal skeleton
what is the function of the splanchnocranium in vertebrates?
supports gills via branchial arches
attachment points for respiratory muscles
what is the function of the splanchnocranium in gnathostomes?
contributes to formation of jaws and hyoid apparatus
supports mouth and functional gills (interposed with pharyngeal slits)
give examples of bones of the splanchnocranium
hyomandibula, meckel’s cartilage, brancial arches
give examples of the bones of the chondrocranium
sensory capsules, occipitals, ethmoid
give examples of the bones of the dermatocranium
orbital, pre/maxilla, nasal, quadrate, jugal, temporal…
what are the major bones that are found around the fenestrae of skulls?
quadratojugal
jugal
squamosal
parietal
postorbital
what is different about the bones associated with the jaws of birds?
they are greatly reduced
what are some common trends with synapsid skulls?
heterodont teeth
many bone fusions/losses
temporal-dentary jaw joint
what bones make up the pectoral girdle?
scapula
(cleithrum)
coracoid
clavicle
what bones make up the forelimb?
humerus
radius
ulna
carpals
metacarpals
phalanges
what bones make up the pelvic girdle?
ilium
pubis
ischium
what bones make up the hindlimb?
femur
(patella)
tibia
fibula
tarsals
metatarsals
phalanges
what are some trends seen in tetrapod evolution?
- reduction/ simplification of the pectoral girdle (reduction of coracoids/ clavicles)
- changes in digit numbers
- development of sesamoid bones (tendon anchoring bones)
what are some trends seen during the evolution of the pectoral girdle?
- loss of cliethrum/ gill parts (= head mobility)
- high variations in clavicle
- reduction/ loss of the interclavicle
domination of the scapula
what are some trends seen during the evolution of the pelvic girdle?
- divergence and enlargement of the three bones
- caudal rotation of the pubis
- opening of the hip socket
-overall is more conservative than pectoral girdle
what are some adaptations of the mammalian design?
- enlarged pectoral girdle
- erect posture (parasaggital gait)
- dorsoventricular flexibility in vertebrae
describe continuum in the context of autopodial posture?
the straightening of the distal joints (like the posture of ungiligrades)
what are some tradeoffs with the different types of autopodial postures?
plantigrades = stable base, shorter stride length
unguligrade = less stable base, longer stride length. lighter distal limb = easy to swing = faster locomotion
what are some limb adaptations which can increase speed and efficiency?
- upright posture/ longer distal limbs
- larger proximal muscles, longer distal tendons
- larger levels ie of the carpals/tarsals
- vertebral dorso-ventral flexibility
