The cells of the human body are structures that can form different structures , including the trophoblast . The trophoblast is a structure that is formed by a set of cells that are found giving shape to the outer layer that surrounds a blastocyst , during the earliest stages of embryonic development that mammals go through. The term comes from the Greek language “trophos” , which means “feed” ; and blast , which refers to the embryonic germ cell .


What is the trophoblast?

Trophoblasts are cells that are specialized in the placenta and are responsible for playing an important role in the implantation process and in the formation of the q interface between the mother and the fetus .

  • Definition
  • features
  • Function
  • Trophoblast layers
  • Development
  • Anterior and posterior trophoblast
  • Trophoblast detachment
  • Diseases
  • Importance


The concept of trophoblast refers to the group of cells that are found forming the outer layer of the blastocyst or the growth of the embryo and that is part of what will later be the placenta . Began his training in very early stages of pregnancy and provides substances nourishing the embryo when it is in development. It is a mixture of cells from the placenta and is responsible for making it possible for the embryo to implant in the endometrium of the uterus.



The main characteristics of the trophoblast are as follows:

  • It serves to implant the blastocyst in the wall of the uterus.
  • Provides nutritional elements to the embryo when it has been implanted.
  • It is present from the beginning of the development of the embryo .
  • It is made up of small folds or holes and chorionic villi.
  • It secretes a series of enzymes that allow cells to enter the lining of the uterus to make nesting of the egg possible.


The trophoblast has a very important role in implantation and placentation . These two processes occur in a correct way as a consequence of the molecular communication that occurs between fetal and maternal tissues, through hormones and membrane receptors . In the implantation of the blastocyst, new types of different trophoblastic cells are generated, one of them is the trophoblast that participates in the exchanges between the fetus and the mother .

The trophoblast, although it does not contribute directly to the formation of the embryo, is a promoter of the placenta that is responsible for establishing a connection with the maternal uterus to allow nutrition of the developing embryo . 

Trophoblast layers

During the implantation process, the trophoblast multiplies, grows and differentiates into two different layers:

  • Syncytiotrophoblast : is the layer external and cells have limits intercellular because they lost their membrane, why, cells are you multinucleate and form cords infiltrating the endometrium. These cells come from the fusion of cytotrophoblast cells and their growth causes the generation of chorionic villi that help increase the surface area to allow adequate flow of nutrients from the mother to the fetus.
  • Cytotrophoblast : layer forms the inner of the trophoblast. It is an irregular layer of ovoid cells that have a single nucleus and are called mononuclear cells . It is located below the syncytiotrophoblast and its development begins from the first week of gestation . The trophoblast makes embryo implantation easier by means of the cytotrophoblast cells. Its correct development is very important to achieve an adequate implantation of the embryo to the uterine endometrium . However, when it grows uncontrollably it can generatetumors .


During the third week , embryonic development includes the development of the trophoblast . Initially, the primary villi are formed by the inner cytotrophoblast which is surrounded by the outer layer of syncytiotrophoblast . Then, the cells found in the embryonic mesoderm go to the primary villi in the third week of gestation, and when the gestation ends, the mesodermal cells begin to singularize to form blood vessel cells . As the process progresses, the hairy capillary system is formed and theplacental villi .

The capillaries that form later come into contact with other capillaries and the newly formed vessels will come into contact with those of the intraembryonic circulatory system . In this way, when the heart begins to beat, the villous system will be ready to supply the oxygen and nutrients necessary for its growth .

The cytotrophoblast reaches the maternal endometrium and comes into contact with hairy stems, forming the outer cytostrophoblastic covering that little by little surrounds the trophoblast and attaches the chorionic plate to the endometrial tissue at the end of the third week of gestation. As the chorionic cavity enlarges, the embryo is attached to the trophoblastic covering by the fixation pedicle , a fairly tight ligation structure. Then the fixation pedicle will become the umbilical cord that will connect the placenta with the embryo .

Anterior and posterior trophoblast

When we talk about an anterior trophoblast we are talking about an anterior placenta , this situation occurs when the placenta is located in the anterior face of the uterus , it is not a disease and only refers to its position in the uterus. When we speak of posterior trophoblast we refer to the posterior placenta that occurs when the placenta attaches to the uterus on the posterior wall . This is a dangerous situation when the placenta develops towards the cervix and is then known as placenta previa .

Trophoblast detachment

It is known as placental abruption and is an emergency situation . It consists of a loss of adhesion of the placenta to the wall of the uterus, generally caused by a hematoma. It is a condition that occurs frequently and is called trophoblast detachment when it occurs during the first two months .


When trophoblastic proliferations occur, tumors such as high-grade endometrioid carcinoma, squamous cell carcinoma, and trophoblastic tumors occur . This tumor is made up of mononuclear trophoblastic cells. There may also be a proliferation of intermediate trophoblastic cells that invade the walls of the blood vessels .

There are diseases that are very rare to appear, such as gestational trophoblast disease, causing the zygote to not form correctly. The hydatidiform mole is a disease that can invade and attack to the uterus and surrounding organs . The neoplasia that occurs most often choriocarcinoma, a form of invasive implantation and pregnancy are less common trophoblastic tumor of the placental site and tumor trophoblastic epithelium .


The trophoblast is of utmost importance during the pregnancy period because it is through it that the implantation of the blastocyst in the uterine endometrium is achieved , although they are not in contact with the mother’s body or with the fetus. Its outer part also produces the hormone HGC which makes it possible to detect pregnancy in blood and urine tests.

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