Lecture 4 Flashcards
List 5 facts of the axial skeleton
Dorsal, Segmented disks separated by mobile joints, Bone or cartilage, Houses the spinal cord,
Develops around the notochord
True or false: Notochords are synapomorphic in chordates
true
Do hagfish and lamprey have nodules resembling centrum?
No, resembling vertebral arches, no body (centrum)
2 pieces of vertebrae evolution
Arches on notochord, Centra (body of the vertebrae)
What is aspondyly?
Vertebrae that lack centra (like the hagfish / fossil gnathostomes)
What is it called when a centra is a single bone fused to other vertebral elements compared to being formed of multiple bones?
Monospondyly vs. diplospondyly or polysplondyly
What are the two fates of the notochord?
the notochord remains intact with the centra surrounding it, In other species the centra is fully ossified and the remnants of the notochord form the gel-like centre of the intervertebral disks
Structure and function of acoelous
Flat ends , Receive and distribute compressive forces
Structure and function of amphicoelous
All surfaces are concave, Allows limited motion in most direction
Structure and function of procoelus
Ball and socket, Extensive motion in all directions without stretching the nerve
Structure and function of hetercoelus
Saddle-shaped at both ends, Extends but doesn’t twist (ex. Bird necks)
What are apophyses?
are processes that extend from the centra or the arches and articulate with other structures
Function of zygopophyses
allow vertebrae to interlock with one another, dictate the strength and flexibility of the vertebral column
Function of Diapophysis and Parapophysis
processes that allow vertebrae to articulate with the ribs
What is regional specialization?
vertebrae in different regions of the vertebral column have different functions and therefore have different forms
What do ribs do? (2)
provide a secure site for muscle attachment, form the thoracic cavity
What does the hemal arch do?
Protects the caudal artery and vein (blood vessels of the tail)
What do extinct sarcopterygians show
Show the same basic trunk vs caudal specialization as other aquatic gnathostomes
What did extant sarcopterygians evolve?
Secondarily evolved very simplified vertebrae with a simple ring around the notochord and supporting neural and hemal arches
Do agnathans have appendages?
they have a tail but no pelvic or pectoral fins
What do paired pectoral fins do?
stabilize the head
How is pectoral girdle fused to the skull?
in ray-finned and cartilaginous fishes (balance)
What can paired appendages help with?
Buoyancy
What do cartilaginous and bony fishes do to achieve natural buoyancy
Density - fats, gases. Dynamic lift - pectoral fins, rostrum
What is a swim bladder?
a gas filled sack that help them achieve neutral buoyancy
Can ray-fins be used for propulsion on land? Can tails be used for propulsion on land?
Not very effectively, yes but it is difficult
How are digits made by appendages?
During embryonic development, all the radial bones move up and polarize over & become the digits of the appendages, Slight change in the genetic program
True or false: almost all amniotes are quadadactyl
False. Pentadactyl
What allows tetrapods to walk without dragging their bellies or tails on the ground
Quadrupedal gait
What is a bi pedal gait
walking on two legs
What posture do early tetrapods have
sprawling posture
What does an upright posture do
allows large animals to support their body weight on land more efficiently
Does bone density in marine mammals increase or decrease, why?
Increases to offset the buoyancy of the lungs
What bone density do larger land animals require?
stronger (larger and more dense) limb and girdle bones to support their body weight against gravity
What happens to bone density in space
lose bone density in space as they no longer need to support their body weight against gravity
Why do bones degrade in space?
Osteocytes are not getting gravity signal - stop building extracellular matrix - skeletons don’t need to support bodies anymore
Tell me about the bone density in amphibious fishes
increased bone density in pectoral girdles
What does vertebral structure do to prevent sagging
balance between flexibility and support
What does zygapophyses do to prevent sagging
interlocking processes provide structural support for the vertebral column, Prevent sag and twisting
What does the atlas and axis do in amniotes
the first 2 cervical vertebrae in amniotes allow the head to move independently of the vertebral column
Why don’t fish need to turn their head?
Fish have non-cranial sensory organs
What do necks allow for in tetrapods
allow separation of the skull and pectoral girdle
Why do thoracic ribs fuse ventrally with a sternum?
Protection, Pectoral muscle attachment, Support for pectoral girdle
How do snakes prevent sagging in the vertebral column
their vertebrae have extra processes
