Freebase(0.00 / 0 votes)Rate this definition: Ibid. Ibid. is the term used to provide an endnote or footnote citation or reference for a source that was cited in the preceding endnote or footnote. This is similar in meaning to idem, abbreviated Id., which is commonly used in legal citation. To find the ibid. source, one must look at the reference preceding it. Anagrams for ibid. Â»
Fertilization and Embryo Development. Following ovulation, the egg is capable of fertilization for only 12 to 24 hours. Contact between the egg and sperm is random. Once the egg arrives at a specific portion of the tube, called the ampullar-isthmic junction, it rests for another thirty hours. Fertilization â sperm union with the egg â occurs in this portion of the tube. The fertilized egg then begins a rapid descent to the uterus.
First, ovulation (i.e., the monthly release of a woman's egg) must occur. Then, the egg must be fertilized. Fertilization describes the process by which a single sperm gradually penetrates the layers of an egg to form a new cell (zygote). This usually occurs in the fallopian tubes and can take up to 24 hours. There is only a short window during which an egg can be fertilized.