Final answer:
An oocyte is released during ovulation and enters the oviduct with the help of cilia and muscular contractions within the uterine tube. Fertilization, if it occurs, takes place in the distal uterine tube. Unfertilized oocytes disintegrate after failing to be fertilized within 72 hours.
Step-by-step explanation:
An oocyte is released from a human ovary and enters the oviduct through a process called ovulation. After puberty, typically one follicle in the ovary matures each month and its primary oocyte completes meiosis I to produce a secondary oocyte, which starts meiosis II. During ovulation, this mature follicle bursts open and the secondary oocyte along with a few granulosa cells are released into the peritoneal cavity. From the peritoneal cavity, the oocyte is swept into the nearby uterine tube, or fallopian tube, by the fimbriae which is the fringelike end of the tube. High concentrations of estrogen during ovulation induce smooth muscle contractions and cilia beating within the uterine tube, which help move the oocyte toward the uterus. The oocyte's journey along the uterine tube must occur quickly, as fertilization needs to happen in the distal tube within 72 hours, otherwise, the unfertilized oocyte cannot survive the journey to the uterus.
If the secondary oocyte is fertilized by a sperm, it completes meiosis II, forming a diploid zygote, and continues towards the uterus for implantation. If not fertilized, the oocyte will not complete meiosis II and will disintegrate.After puberty, one follicle a month matures and its primary oocyte completes meiosis I to produce a secondary oocyte, which begins meiosis II. During ovulation, the mature follicle bursts open and the secondary oocyte leaves the ovary and enters a Fallopian tube. If the secondary oocyte is fertilized by a sperm, it quickly completes meiosis II and forms a diploid zygote, which will continue through the Fallopian tube. The zygote will go through multiple cell divisions before reaching and implanting in the uterus. If the secondary oocyte is not fertilized, it will not complete meiosis II, and will soon disintegrate.
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