Transcript BIO 2310
Axial Skeleton - Vertebrae
Locomotion
Protects spinal cord
Suspends trunk
Vertebrae
Centrum
Body of vertebra
Surrounds or replaces notochord
Centrum shape
Amphicelous (most fish, tailed amphibians)
Opisthocelous (terrestrial salamanders, gar)
Acelous (mammals)
Procelous (reptiles, frogs)
Vertebrae
Vertebral arch
Neural arch
Neural spine = spinous process
Neural canal = vertebral canal
Vertebrae
Hemal arch
Chevron bone in amniotes
Ventral archway for caudal blood vessels
Hemal spine
Vertebrae
Transverse process
Diapophysis
Vertebrae
Zygaphophyses
Tetrapod feature
Prezygapophyses – cranial
Postzygapophyses - caudal
Development of vertebrae
Ancient
Sclerotomes around notochord
Intersegmental from the somites
Cartilage replacement of notochord
Bone replacement of notochord
Vertebrae in advanced fish
Centrum replaces notochord
Diplospondyly in tail
Vertebrae in fish
Regional differentiation
Dorsal = Trunk
Caudal = tail
Vertebrae - fish
Craniovertebral joint
No movement
Vertebrae - Amphibians
Terrestrial life
Spine must support body
Resists bending but provides mobility
Phylogeny of tetrapod vertebrae
Tetrapod centrum is the descendant of the
Pleurocentrum, not the intercentrum
Vertebrae - amphibians
Zygapophyses
Vertebrae - amphibians
Regional differentiation
Cervical – usually one
Trunk = dorsal – ribs present
Sacral – one
Caudal – no zygapophyses
Urostyle – fused post-sacral vertebrae in
anurans
Skeletal support
Cervical vert.
Trunk vert.
with ribs
Sacral vert.
Caudal vert.
Vertebrae - amphibians
Craniovertebral joint
1-2 occipital condyles
Vertebrae - Reptiles
Centrum replaces notochord
Procoelous centrum
Pleurocentrum is phylogenetic ancestral
centrum
Vertebrae - Reptiles
Zygapophyses
Not in tail
Vertebrae - reptiles
Cervical – 8 including atlas and axis
Dorsals = Trunk (thoracic and lumbar)
Sacral – 2 for stronger support
Caudal
– Chevron bone = hemal arch
– Autonomy
Vertebrae - reptiles
Craniovertebral joint
Ball & socket type of joint
Single occipital condyle
Vertebrae - reptile
Atlas = C1
Axis = C2
– Odontoid process for rotation
Proatlas in crocodiles anterior to atlas
Vertebrae - Birds
Centrum is heterocoelous
Vertebrae - birds
Numerous cervical vertebrae
Single occipital condyle
Trunk = Thoracic vertebrae (tend to fuse)
Synsacrum
– Last thoracic, all lumbar, 2 sacral, some caudal
Caudal vertebrae
– Pygostyle supports tail feathers
Vertebrae - Mammals
Centrum is acelous
7 cervical
Thoracics vary
Lumbars vary
Sacrum 3-5
Caudal
– Chevron bone
– Coccyx
Vertebrae - Mammal
Intervertebral disc
Fibrocartilage
Pulpy nucleus
Vertebrae - Mammal
Craniovertebral joint
2 occipital condyles
Atlas
Axis
Flex, extend, circle, rotate
Key Points – Evolutionary trend
of vertebrae
Regional differentiation?
Head/neck?
Sacral stability?
Zygapophyses?
Loss of notochord?