In humans, the yolk sac is the
site of origin for blood cells and primordial germ cells. The human yolk sac is
a membrane located outside the embryo and it is connected by a tube through the
umbilical opening to the embryo's midgut. The yolk sac serves as an early site
for the formation of blood and in time, is incorporated into the primitive gut
of the embryo.
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synthetic fiber
Explanation:
because it contains chemicals
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The idea model is used to for relationships between variables, such as time and distance, that can be graphed or be placed into an equation. A physical model, on the other hand, is generally used for objects, such as a cell, to show the various parts and their orientation in respect to each other. A computer model is used to track weather patterns and other factors to predict natural events.
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