Post-Cranial Skeleton Flashcards
post cranial skeleton (2)
- axial skeleton
- appendicular skeleton
axial skeleton (4)
- vertebral column
- notochord
- ribs
- sternum
appendicular skeleton (2)
- paired fins or limbs
- girdles
neural arch
- protects spinal cord
hemal arch
- protects blood vessels/dorsal aorta
processes
- spine, zygapophyses, diapophyses
- provide sites for muscle attachment or specialized regions for articulation with other skeleton elements
agnatha vertebral column (3)
- large and prominent notochord
- hagfish do not have vertebrae
- petromyzontida have cartilaginous vertebra consisting of small neural arches on the dorsal surface of the notochord; no centra or hemal arches
chondrichthyes vertebral column (3)
- cartilaginous vertebral column
- each vertebra has a centrum
- centra provide major axial structural support for body and surround the notochord
actinopterygii vertebral column (3)
- ossified endochondral bone
- centra provide major axial support for the body and surround the notochord
- large neural spines and ribs provide sites for muscle attachment
sarcopterygii vertebral column (2)
- ANCESTRAL: ossified (endochondral bone) and had centra surrounding notochord
- EXTANT: centra reduced or secondarily lost; neural and hemal arches rest on large and prominent notochord
tetrapoda vertebral column (2)
- solid centra that does not surround the notochord
- composed of ossified (endochondral bone) and provides axial structural support for the body
notochord presence in: (2)
- chondrichthyes
- hollow centra that notochord passes through
- notochord thickens to provide a pad between each vertebrae
notochord presence in: (2)
- actinopterygii
- hollow centra that notochord passes through
- notochord thickens to provide a pad between each vertebrae
notochord presence in: (2)
- tetrapods
- articular ends of centra capped with intervertebral bodies/pads
- intervertebral bodies composed of cartilage/fibrous connective tissue
notochord presence in: (2)
- mammals
- articular ends of centra capped with pads called intervertebral disks
- composed of cartilage, fibrous connective tissue, and notochord remnants
what is the purpose of intervertebral disks
- cushion between vertebrae to assist in shock absorption
which taxa has a regionalized vertebral column
- gnathostomes
vertebral column regionalization: chondrichthyes
- two regions: trunk and caudal
vertebral column regionalization: actinopterygii
- two regions: trunk and caudal
vertebral column regionalization: sarcopterygii
- two regions: trunk and caudal
how do trunk and caudal vertebrae differ? (2)
- trunk: rib attachment sites, only have neural arch/spine
- caudal: hemal arch/spine and neural arch/spine
notochord/vertebral column main function
- lateral undulations
lateral undulations (2)
- alternating contractions of muscles on each side of body produce that provide propulsive force to push the body froward
- notochord/vertebral column serve as a firm, but flexible rod that axial muscles pull from side to side to bend body, moving tail back and forth
which taxa use notochord to produce lateral undulations (3)
- sarcopterygii
- petromyzontida
- myxinoidea
which taxa use the vertebral column to produce lateral undulations (3)
- actinopterygii
- tetrapoda
- chondrichthyes
appendicular skeleton: agnathans
- do not have appendicular skeleton
appendicular skeleton: gnathostomes
- paired fins or limbs and girdles
which taxon have appendicular skeleton consists of paired fins and girdles (3)
- chondrichthyes
- actinpterygii
- sarcopterygii
paired fin composition (2)
- proximal regions: fins are supported by relatively thick sturdy skeletal elements
- distal regions: fins are supported by thin ray fins; chrondrichthyes have keratin ray fins
girdles (3)
- attachment sites for muscles of the appendages
- stabilize the appendages by bracing them against the body
- must be braced by attachment to another skeletal structure or by embedding in muscles
pectoral girdle attachment
- actinopterygii
- sarcopteryigii
- chonrichthyes
- tetrapods
- actinopterygii and sarcopteryigii:: attached to the dorsal, posterior region of the skull
- chonrichthyes: does not attach to the skull or vertebral column; embedded in the muscle of the body wall
- tetrapods: loss of girdle attachment to the skull; axial skeleton is suspended from girdle by muscles
pelvic girdle attachment
- actinopterygii
- sarcopteryigii
- chonrichthyes
- tetrapods
- actinopterygii, sarcopteryigii, chonrichthyes: pelvic girdle does not attach directly to vertebral column; embedded in the muscles of the body wall
- tetrapods: pelvic girdle fused to sacral region of vertebral column
what is the result of lateral undulation in aquatic environments (4)
propulsion from lateral undulations of tail produces thrust that propels the body forward; but it can also cause:
- pitch
- yaw
- cause rolling of animal
pitch
- shift the angle of the head dorsally or ventrally
yaw
- wag the head left and right
paired fin function: chondrichthyes (3)
- provide stability during locomotion by preventing roll, pitch and yaw
- active adjustment of angle for steering, allowing shark to control direction while swimming
- claspers
claspers (2)
- on pelvin fins
- act as intromittent organs: they transfer sperm to the female during copulation for internal fertilization
paired fin function: actinopterygii (4)
- used for stabilization (minimize roll, pitch, yaw) while swimming using lateral undulations of tail for propulsion
- are used for steering when swimming
- are used to maintain body position in the water when stationary and for braking
- used for propulsion in some; very precise and slow
teleotomi: ray fins (2)
- actinopterygii
- thin layer of skin and connective tissue supported by slender fin rays of bone or cartilage
teleostomi: fleshy fins (4)
- sarcopterygii
- fins supported by series of bones that articulate using mobile joints; muscles that move these bones extend into the fin
- distal ends usually have fin rays supporting a thin layer of skin and connective tissue
- advantage: highly maneuverable; used for precise swimming, pivoting and maneuvering in shallow waters, holding position on bottom habitats in deep water, walking along bottom surfaces
fin rays (2)
- found in chondrichthyes, actinopterygii and sarcopterygii
- increase surface area of fin, making it better for pushing/propelling against water
support of weight: aquatic vertebrates
- body is evenly supported by water all around them (buoyancy), so skeleton does not play major role in supporting body weight
support of weight: terrestrial vertebrates (2)
- skeleton is crucial for supporting body weight
- to support body against gravity, terrestrial animals: rest ventral body surface on the ground OR use the legs as pillars to hold up the body
how did the girdles and paired appendages change from sarcopterygii to tetrapods (2)
- were enlarged and became more completely ossified
- done to increase support for animal body weight and make it sturdier
how did the thin fin rays change from sarcopterygii to tetrapods (2)
- thin fin rays supporting distal tips of fins were replaced with digits
- better weight support; better balance and mobility
how did the pectoral girdle attachment change from sarcopterygii to tetrapods (2)
- lost attachment to the skull and became suspended by muscles
- more flexibility and better locomotion
how did the pelvic girdle attachment change from sarcopterygii to tetrapods (3)
- fused to the sacral region of the vertebral column
- reinforced and strengthens structures so they can withstand powerful forces generated by hind limbs
- propulsive force generated by hind limbs is transmitted more efficiently to axial skeleton, propelling entire body forward
what changees occurd from sarcopterygii to tetrapods (4)
- girdles and appendages enlarged and completely ossified
- thin fin rays replaced by digits
- pectoral girdle lost attachment to skull
- pelvic girdle fused to sacral region of vertebral column
sprawled limb posture (3)
- sauropods (except aves) and amphibians
- rest ventral body surface on ground when stationary so vertebral column doesn’t need to bridge weight of the bofy
- during locomotion, they must use limbs to support body weight
erect limb position
- most mammals and birds (aves)
- use limbs as pillars to support the body weight during locomotion and when stationary
the stable arch (3)
- quadrapedal mammals
- vertebral column acts as bridge that transfer weight of internal organs to the legs
- epaxial muscles that attach to neural spines of vertebrae help pull vertebral column into an arch, stabilizing so it can effectively bridge weight to limbs without sagging
vertebral column regionalization: tetrapods
- 4 regions: caudal, sacral, trunk, cervical
vertebral column regionalization: amniotes
- 5 regions: cervical, thoracic, lumbar, sacral, caudal
cervical region
- differentiated for cranial mobility
- in amniotes, additional cervical vertebrae further increase neck flexibility (more mobile joints)
sacral region (2)
- differentiated for attachment of pelvic girdle
- some have single sacral vertebrae, where others have 2+ that fuse and form a sacrum for increased strength and durability
how to differentiate between thoracic and lumbar vertebrae
- thoracic vertebrae will have processes for rib attachment
synsacrum
- birds
- sacral, lumbar and several thoracic and caudal vertebrae fuse together to form the synsacrum
- fuses with pelvic girdle, producing a strong and stable platform to support the body during flight and to withstand the forces of landing
- strong, but relatively light in weight
cervical vertebrae of mammal
7 :
- 1 axis
- 1 atlas
- 5 regular
atlas (4)
- in tetrapods
- most anterior vertebrae
- does not have a centrum
- articulates with occipital bones of the skull, allowing the skull to rock in a nodding motion
axis (3)
- in amniotes
- second most anterior vertebrae
- has an odontoid process: an anterior projection that inserts into the neural canal of the atlas, allowing the head to turn from side to side
zygopotheses (3)
- tetrapod vertebrae
- interlocking structures help to prevent twisting (torque) of vertebral column to prevent damage to spinal cord
- postzygapophyses of vertebra articulate with prezygapophyses of posterior vertebrae
postzygapophysis (2)
- articulates on dorsal side and projects posteriorly
- “high five”
prezygapophysis (2)
- articulates on ventral side and projects anteriorly
- “low five”
sternum (2)
- composed of cartilage/endochondral bone
- only in tetrapods; however, it is the result of convergent evolution
sternum: aves (2)
- has a large keel for attachment to flight muscles
- in flightless birds, the keel tends to be reduced in size compared to flying birds
ribs
- gnathostomata
- composed of cartilage or endochondral bone
- protect vital and delicate internal organs
ribs: amphibians
- ribs do not articulate with sternum
