Axial skeleton Flashcards
Centra type: Chondrichthyes
Amphicoelous
Procoelous vertebrae (def)
Anterior: concave
Posterior: convex
Entire centrum solid with cartilaginous intervertebral disks
What structure carries blood vessels to the head through the cervical vertebra(e)?
Transverse foramen
Describe vertebrae of gnathostomes, generally (compared to early vertebrates & agnathans)
Vertebrae are main axial support, attachment site for body muscles
Amphicoelous vertebrae (def)
Centra concave on both ends, surrounds notochord from head to tail
Effect of neural spine angle on function
Grow to better withstand forces by making them compressive
Describe agnathan ribs
Non-existent
Form & function of ribs in gnathostomes
Cartilage/replacement bone struts
Muscle attachment, protect viscera
Opisthocoelous vertebrae (def)
Anterior: convex
Posterior: concave
Centrum solid, with cartilaginous intervertebral disks
Who has lots of cervical vertebrae & why?
Aves, parareptilia -> allows greater flexibility
Centra type: Osteichthyes
Amphicoelous
Describe the axial skeleton of Myxinoidea
None -> 2° loss
Sacrum: structure & function
Fused sacral vertebrae supporting pelvic girdle
Strong -> can withstand hind limb forces
Who has procoelous or opisthocoelous vertebrae?
Most sauropsids (except aves), many amphibians (not all)
Heterocoelous vertebrae (def)
Both ends saddle-shaped
Vertebrae can move in different directions relative to each other (flexible)
Cartilaginous intervertebral disks
Centra type: Mammals
Acoelous
Describe the axial skeleton of Petromyzontida
DORSAL (only) cartilaginous arches protecting spinal cord; no muscle connection or body support
Describe the axial skeleton of Osteichthyes
Ossified
Centra: Major axial support, surrounds notochord
Neural arches & hemal arches
Neural spines & ribs are large for muscle attachment
Function of intervertebral ligaments
Control/limit flexibility & movement of vertebral column
Who has an atlas?
Tetrapods
Function of neural spines in terrestrial mammals
Muscle attachment to pull vertebral column into arch to direct compressive forces into centra, then down into legs
Describe amniote ribs
Some, at least, connect to sternum
Centra type: Sauropsids other than Aves
Procoelous or opisthocoelous
Acoelous vertebrae (def)
Flat on both ends
Transverse foramen (def)
Holes in cervical vertebrae to carry blood vessels to head
Synsacrum structure
Fused sacral, lumbar, some thoracic & caudal vertebrae in aves
Describe bird sternum, function
Large carina/keel - for attachment of flight muscles
Describe the atlas
- most anterior cervical vertebra
- no centrum
- allows nodding motion
- seen in all tetrapods
Describe fish ribs
single-headed
Define zygapophyses & give their function
Processes on the anterior and posterior neural spine
Lock with those on adjacent vertebrae to prevent torsion
Describe axial skeleton regionalization in gnathostome fish and what it says about them
Trunk (has ribs), caudal (has no ribs)
Similar throughout because 1 function: muscle attachment for swimming
Who has amphicoelous vertebrae?
Chondrichthyes, osteichthyes, some amphibians
Function of synsacrum
Stability in flight
Strength in landing
Can be thinner/lighter b/c stronger, don’t need muscles & ligaments to maintain posture
Describe vertebrae of early vertebrates, agnathans (general)
notochord acts as main axial support, vertebrae are cartilaginous arches protecting spinal cord (neural arches) and dorsal aorta (hemal arches)
Who has acoelous vertebrae?
Mammals
Describe the axial skeleton of Chondrichthyes
Cartilaginous
Centrum: support, surrounds notochord
Neural arches: protect spinal cord
Hemal arches (caudal vertebrae), ribs (trunk vertebrae): protect dorsal aorta & other blood vessels
Centra type: Mammals
Acoelous
Describe the axis
2nd cervical vertebra
Has odontoid process projecting anteriorly into atlas neural canal;
Allows head rotation
Describe amphibian ribs
Short (don’t connect to sternum)
Describe axial skeleton regionalization in early tetrapods and what it says about them
Cervical: allows cranial mobility (not needed in fish b/c decreases streamlining)
Trunk
Sacral: for pelvic girdle attachment
Caudal
How does neural spine height affect function?
Increases length of lever arm -> same muscle can do more work in pulling column into arch
Who has zygapophyses?
Tetrapods
Centra type: Amphibia
Most: procoelous or opisthocoelous
Some: amphicoelous
Describe aves ribs
Uncinate processes connect vertebral (costal) ribs, expanding ribcage faster
Describe axial skeleton regionalization in early amniotes and what it says about them
Cervical (cranial motility), thoracic (ribs), lumbar (no ribs), sacral (pelvic girdle attachment), caudal
-Lumbar allows back to flex as hind limbs push forwards for more efficient propulsion; decreases protection
Function of sternum
Support & stabilize pectoral girdle
Who has an axis?
Amniotes
Who has heterocoelous vertebrae?
Aves
Effect of locomotion method on sternum size
Bigger if forelimbs important in locomotion (lots of forces)
