Flashcards in Gastrulation Deck (28)
What is gastrulation?
Process by which blastula is transformed into an embryo , with tissue layers and body axis.
What is the embryo called during gastrulation?
What are the three layers that may form (only two in diploblastic)?
Mesoderm, endoderm, ectoderm
What is the endoderm?
Inner layer, forming digestive tract, circulatory tract and respiratory tract
What is the ectoderm?
outer layer, forming epidermis and nervous system
What is the mesoderm?
Middle layer, forming bone, muscle, liver, heart, blood vessels
What is the result of gastrulation?
Some of the cells at or near the surface of the blastula move to an interior location and three cell layers are established, allowing cells to interact in new ways and leads to generation of body organs
Where does gastrulation beginning sea urchins, birds and frogs, and what happens?
At the vegetal pole, where individual cells detach from the blastocoel wall and enter the blastocoel as migratory cells.
What are mesenchyme cells?
Loosely organised migratory mesodermal tissue that develops into connective and skeletal tissue
How does the vegetal plate form?
Cells remaining at the vegetal pole after gastrulation flatten slightly
What is invagination?
Vegetal plate buckles inwards as a result of cell shape changes, cells are then extensively rearranged and invagination deepens, forming a narrow blind ended tube
What is the archenteron?
Blind ended tube formed in invagination, open end is called the blastopore
What does the blastopore become in proteostomes?
How does the mouth form in deuterostomes?
A second opening forms when the opposite end of the archenteron reaches the inside of the ectoderm and the two laters fuse, producing a rudimentary digestive tube
Why are mechanisms of gastrulation more complex in frogs?
Because of the large yolky cells in the vegetal hemisphere
Where does gastrulation begin in frogs?
On the dorsal side of the blastula when a group of cells begins to invaginate
What is the dorsal lip?
Part above the crease in frog gastrulation which becomes the dorsal side of the blastopore
What is involution?
Layers at the surface of the embryo roll over the edge of the lip into the interior of the embryo - becomes mesoderm and endoderm
What happens to the blastocoel during gastrulation in frogs?
Collapses as it is displaced by the archenteron that is formed
What happens to the circular lip of the blastopore once gastrulation is completed?
Surrounds a yolk plug consisting the outer nutrient laden cells
Why is gastrulation different in chicks?
The inward movement of cells is affected by the large mass of yolk pressing against the bottom of the embryo
What is the epiblast?
Upper layer of gives rise to the three primary germ layers and extra embryonic layers
What is the blastoderm stage?
Consists of upper and lower layers, epic and hypoblast, lying atop the yolk mass.
What happens during gastrulation in chicks?
Some epiblast cells move inward at the blastoderm and then detach and move inward toward the yolk. Forms the primitive streak
What is the primitive streak?
Functionally equivalent to blastopore in frogs, but oriented differently. An opening by which the cavity of the gastrula communicates with the exterior.
What is the function of the hypoblast?
Seems to direct the formation of the primitive streak before the onset of gastrulation
When is gastrulation complete?
When all germ layers have formed