Lecture 2: Chordates

Blastula

early developmental stage of animal embryo when it is a hollow ball of cells

Gastrula

later embryonic stage when the blastula invaginates to form an inner gut tube

Archenteron

early or rudimentary gut tract of an embryo

Blastopore

opening of the central cavity of an embryo during gastrulation

Blastocoel

central cavity of the blastula

Ectoderm

external tissue layer of embryo; gives rise to epidermis and nerves in adults

Endoderm

innermost tissue layer of embryo; gives rise to gut lining + organs

Mesoderm

middle embryonic tissue layer; gives rise to diverse organs like muscle

Diploblastic

animals having only two embryonic tissue layers (many non deuterostomes)

Triploblastic

animals having three embryonic tissue layers (like deuterostomes)

Enterocoely

formation of coelom from out pocketings of the archenteron

Notochord

rod like, rigid tube supporting the skeleton of chordates

Dorsal hollow nerve cord

central nervous system structure dorsal to the notochord

Post anal tail

tail that extends past the anus; used for locomotion (+ burial, in some cases)

Pharyngeal pouch or slits (pharynx)

feeding structure in chordates, used like a sieve for filtering

Endostyle

longitudinal, ciliated groove in pharynx; used to gather food (homologous w/ thyroid)