| 31. | Where does that yolk sac come from?
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| 32. | AFP is a major plasma protein produced by the yolk sac and the liver during fetal development.
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| 33. | In the first two days, too weak to lift its neck, the baby feeds off the yolk sac.
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| 34. | Reproduction in the finless sleeper ray is viviparous, with the embryos sustained through gestation by a yolk sac.
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| 35. | Eventually, the yolk sac is completely absorbed and the larvae begin to see and catch their own prey.
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| 36. | However, it is difficult to detect the number of yolk sacs, because the yolk sac disappears during embryogenesis.
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| 37. | These cells can develop into a frankly malignant tumor known as yolk sac tumor or endodermal sinus tumor.
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| 38. | For the first few days, they live on the yolk sac while their digestive systems continue to develop.
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| 39. | A newly conceived embryo is sustained by a yolk sac and emerges from its egg capsule at long.
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| 40. | However, it is difficult to detect the number of yolk sacs, because the yolk sac disappears during embryogenesis.
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