Embryogenesis and Development Flashcards
What is the ampulla?
the widest part of the fallopian tube where fertilization occurs
Describe the fertilization reaction
(1) Sperm meets the secondary oocyte in fallopian tube
(2) Binds and releases acrosomal enzymes which allow penetration of the corona radiata and zona pellucida
(3) Sperm comes into contact with cell membrane and forms acrosomal apparatus
(4) Cell membrane is penetrated and the sperms pronucleus enters the oocyte
(5) Depolarization due to fusion initiates a wave of calcium which initiates the cortical reaction
(6) Cortical granules open and cause a cortical reaction which depolarized the cell membrane
(7) This reaction lifts the vitalline layer away from the egg plasma membrane creating the fertilization envelope
What is the fast block to polyspermy?
When the sperm and egg membranes fuse together the egg plasma membrane is depolarized for a few seconds, blocking any other sperm
What is the slow block to polyspermy?
When the cortical reaction causes a lifting of the vitalline membrane and create the fertilization envelope
What is cleavage?
the step after fertilization where the zygote undergoes rapid mitotic cell divisions to form an embryo of the same size, just with more cells
What are the two types of cleavage?
Indeterminate - results in cells that can still develop into complete organisms and not a specific kind of cell
Determinate - cells whose fates are already decided and will develop in a specific kind of cell
What is a morula?
a solid ball of cells that is formed after several divisions of the embryo
What is a blastula?
a hollow ball of cells with a fluid filled inner cavity that is formed by blastulation, the step after cleavage
What is a blastocoel?
the inner fluid filled cavity of a blastula
What is a blastocyst?
the mammalian version of a blastula
What are trophoblast cells?
they surround the blastocoel and give rise to the chorion and later placenta
What is the inner cell mass?
mass of cells that is inside the blastocoel, surrounded by trophoblast cells, and will give rise to the organism itself
What is the chorion?
(1) surrounds the embryo and yolks sac, facilitates exchange of oxygen and CO2 between embryo and external environment
(2) extraembryonic membrane that develops into the placenta and arises from the trophoblastic cells
What are chorionic villi?
microscopic fingerlike projections that penetrate the endometrium and help develop the placenta and support gas exchange
How does the umbilical cord work?
It has one vein that carries freshly oxygenated blood from placenta to embryo and two arteries that carry unoxygenated blood and waste away
Name four extraembryonic membranes
chorion, yolk sac, allantois, amnion
What does the yolk sac do?
supports the embryo until the placenta is functional and site of early blood development
What does the allantois do?
(1) stores nitrogenous wastes produced by embryo and facilitates respiration in combination with chorion
(2) involved in early fluid exchange between embryo and yolk sac. Eventually becomes part of umbilical cord
What does the amnion do?
(1) surrounds the embryo in an aqueous environment to protect from mechanical shock and support hydration
What is gastrulation?
the generation of three distinct cell layers
How is a gastrula formed?
The circular cell will begin to fold into itself, with one side of the membrane getting closer to the opposite and will eventually form a horseshoe shape
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What is the archenteron?
This pathway that was formed by in the folding inward of the membrane of the blastula and will eventually form the gut
What is a blastopore?
It’s just the opening of the archenterion, or the entrance to the invagination or future gut
What does the blastopore develop into in deuterstomes?
the blastopore becomes the anus