chordata Flashcards
Synapomorphies of Chordata
- -notochord
- -dorsal, hollow, fluid-filled nerve-cord
- -paired pharyngeal clefts/grooves, separated by pharyngeal arches
- -post-anal tail in every embryo
notochord
- -first skeletal element
- -vacuolated cells enclosed by fibrous connective tissue
- -axially incompressible, enables flexion when swimming
position of notochord
vertebrae form around notochord (and nerve cord)
fate of notochord
PERSISTS: protochordates, hagfishes, lampreys, other “fish”
PERSISTS, REDUCED: salamanders
OBLITERATED: frogs, amniotes
Mammals - remnant of notochord present in intervertebral spaces
DHFF CNS
becomes CNS ins most; peripheral sensory and motor nerves communicate/connect to CNS
paired pharyngeal clefts/grooves, separated by pharyngeal arches
- -clefts are posterior to oral cavity, anterior to esophagus
- -clefts usually form pharyngeal slits, connect pharynx interior to outside (or to atrium)
fate of pharyngeal slits and arches
protochordates: straining device
fish, juvenile amphibians, and perennibranchiate amphibians: walls of slits develop into gills - thus called branchial slit/branchial arch/gill slit/gill arch
lunged adult amphibians and all amniotes: anterior slit forms the Eustachian tube and middle ear chamber; posterior slits usually don’t open
soft tissue in pharyngeal arches
contributes to glands: tonsils, parathyroid, ultimobranchial bodies, thymus
parathyroid
produces parathormone which increases blood calcium and stimulates osteoclast activity
ultimobranchial bodies
produces calcitonin which decreases blood calcium and inhibits osteoclast activity
become parafollicular cells in mammal thyroid
skeleton and muscles of arches
contribute to muscles of face, embryonic cartilage skeleton of lower jaw, three middle ear ossicles, skeleton and muscles of tongue and larynx, and cartilaginous tracheal rings
cervical fistula/cysts in humans
fistula: abnormal channel connecting an organ to another surface
post-anal tail in every embryo
usually persists in adults
