Find out what the HAIRY ZONE is

The female gamete or oocyte is a large, immobile cell. The oocyte is made up of a nucleus, which carries maternal genetic information, and yolk, a reserve substance that will nourish the cells of the zygote during the first divisions. Surrounding the oocyte we can find two layers: the zona pellucida and the corona radiata. Closer to the oocyte is the zona pellucida, a layer of gelatinous-looking substances whose function is to protect the oocyte; further afield, the corona radiata, a layer of cells that, among other things, help build the placenta and the formation of female sex hormones. In this lesson from a TEACHER we will focus on reviewing the zona pellucida, its simple definition and its functions more general.

The human oocyte is formed as we saw before by two parts: the kernel and the yolk. Due to the large amount of yolk in the human oocyte, this cell is large and cannot move easily so the journey from the ovary, through the fallopian tubes to the wall of the uterus where it sticks (implants) once fertilized, it is not easy. To protect it all the way, the oocyte has developed an outer covering called the zona pellucida. The

zona pellucida It is a gelatinous layer that sticks to the oocyte to protect it.

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The zona pellucida appears when the oocyte has formed but when does it disappear? As we have seen previously, the zona pellucida is maintained during fertilization but also afterwards, during the zygote stage. The zona pellucida disappears on the fifth day after fertilization, during a stage called the blastocyst stage. During this stage, the zygote has divided and has formed something like a ball, made up of cells except for an "air pocket" or cavity that appears in one part. This cavity is called a blastocele, and it is what makes the necessary pressure for the zona pellucida to rupture and implantation can occur. In addition to the pressure caused by the blastocele, there are also substances called enzymes on the wall of the uterus, that are responsible for breaking the zona pellucida from the outside while the blastocele swells and puts pressure to leave.

Once the blastocyst leaves the zona pellucida and implants itself in the maternal uterus, this mass of cells that will form the future baby is called an embryo.