Semana 3 de embarazo

In this article you will find:

  • Segmentation in week 3 of pregnancy
  • When does occurs the segmentation?
  • Stages of segmentation
  • Blastogenesis

The human development starts in this week, when occurs the fertilization of the egg, which is complete when you mix the maternal and paternal chromosomes. The stimulus of fertilization takes out the oocyte from its state of rest, thereby leading to remove part of your DNA, and activates it, favoring the constitution of the zygote.

Segmentation in week 3 of pregnancy

The response to fertilization is the segmentation of the zygote, which consists of mitotic divisions repeated the zygote, which usually causes a rapid increase in the number of cells called blastomeres, which become smaller with each division.

The blastomeres are oval-shaped to rounded and edges are relatively smooth. Not all have the same size, but they denote the same aspect.

When does occurs the segmentation?

  • The segmentation occurs during the passage of the zygote along the uterine horn into the uterus and ends between 5 and 6 days later.
  • The purpose of the segmentation coincides with the structuring of the blastocyst, which consists of around 110 cells.

Stages of segmentation

  • Zygote.
  • 2 blastomeres.
  • 4 blastomeres.
  • Morula.


The little time that penetrated the morula in uterus (4 days after fertilization), between the blastomeres displayed a fluid-filled space called the cavity of the blastocyst. As the fluid increases, the blastomeres are separated into 2 parts:

  • A layer of outer cells thin called trophoblasts that forms the embryonic placenta.
  • A group of blastomeres, which is located in the center, known as a mass of inner cells, which give rise to the embryo.

The blastocyst increases in size rapidly as it floats freely in the uterus and is nourished by secretions of the uterine glands.

Read also: Create artificial wombs for the big premature

Towards the end of this week, the zygote human has gone through the stages of morula and blastocyst and has started her nest in the mucosa of the uterus, where it implants to form on the surface of the compact layer of the endometrium and is nourished by maternal tissues.

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