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Question
In human female, the blastocyst
In human female, the blastocyst
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Solution
The correct option is B gets nutrition from the uterine wall even before implantation
After fertilization, the resulting one-celled zygote repeatedly undergoes divisions by a special type of mitosis called cleavage, as it travels by taking 4 days towards the uterus.
Cleavage or segmentation of zygote results in the production of blastomeres. The zygote has enormous cytoplasm, this gets reduced by the cleavage.
Cleavage divides the one-celled zygote into two and subsequently into 4, 8, and 16 celled stages. The stage of 8-16 cells is called a morula. Morula floats in the uterine lumen for three days. Glycogen rich secretion from the glands of the endometrium enters the floating morula through zona pellucida for nourishment. This nutrient-rich fluid secretion of zona pellucida is known as uterine milk.
Morula further undergoes mitotic divisions and increases the number of the blastomeres inside the fixed cytoplasmic mass of the original zygote. The embryo keeps on multiplying by mitotic division and forms a cavity within the cell mass. The cavity is called blastocoel and the embryo is termed the blastocyst. Now the blastocyst needs to hatch out from the zona pellucida layer for implantation. The trophoblast layer of the blastocyst gets implanted into the endometrium, not the morula. Uterine milk is a nutrient-rich secretion produced by the endometrial gland of the uterus that nourishes the young embryo before implantation. Implantation occurs in the endometrium layer of the uterus around the 7th day of fertilization. The endometrium is the inner layer of the uterus whereas the myometrium is the middle muscle layer which helps in parturition (childbirth).
Figure: Stages in implantation
After fertilization, the resulting one-celled zygote repeatedly undergoes divisions by a special type of mitosis called cleavage, as it travels by taking 4 days towards the uterus.
Cleavage or segmentation of zygote results in the production of blastomeres. The zygote has enormous cytoplasm, this gets reduced by the cleavage.
Cleavage divides the one-celled zygote into two and subsequently into 4, 8, and 16 celled stages. The stage of 8-16 cells is called a morula. Morula floats in the uterine lumen for three days. Glycogen rich secretion from the glands of the endometrium enters the floating morula through zona pellucida for nourishment. This nutrient-rich fluid secretion of zona pellucida is known as uterine milk.
Morula further undergoes mitotic divisions and increases the number of the blastomeres inside the fixed cytoplasmic mass of the original zygote. The embryo keeps on multiplying by mitotic division and forms a cavity within the cell mass. The cavity is called blastocoel and the embryo is termed the blastocyst. Now the blastocyst needs to hatch out from the zona pellucida layer for implantation. The trophoblast layer of the blastocyst gets implanted into the endometrium, not the morula. Uterine milk is a nutrient-rich secretion produced by the endometrial gland of the uterus that nourishes the young embryo before implantation. Implantation occurs in the endometrium layer of the uterus around the 7th day of fertilization. The endometrium is the inner layer of the uterus whereas the myometrium is the middle muscle layer which helps in parturition (childbirth).
Figure: Stages in implantation Suggest Corrections
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