trophoblast

Examples of trophoblast in the following topics:

• Trophoblast Development

  • Trophoblasts are the outer layer of cells that provide nutrients to the embryo and form part of the placenta.
  • This layer of trophoblasts is also collectively referred to as the trophoblast, or, after gastrulation, the trophectoderm, as it is then contiguous with the ectoderm of the embryo.
  • Cytotrophoblast in the tips of villi can differentiate into another type of trophoblast called the extravillous trophoblast.
  • Extravillous trophoblasts grow out from the placenta and penetrate into the decidualized uterus.
  • Trophoblast., u.e.

• Development of the Extraembryonic Coelom

  • It is located between Heuser's membrane and the trophoblast.
  • The extra-embryonic coelom (or chorionic cavity) is a portion of the conceptus consisting of a cavity between Heuser's membrane and the trophoblast.
  • The chorionic plate is composed of an inner layer of somatopleuric mesoderm and an outer layer of trophoblast cells.
  • It consists of an extra-embryonic mesoderm and two layers of trophoblast and surrounds the embryo and other membranes.
  • Chorionic villi are at first small and nonvascular, and consist of only trophoblast, but they increase in size and branch.

• Blastocyst Formation

  • The blastocyst possesses an inner cell mass (ICM), or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast, which later forms the placenta.
  • The trophoblast surrounds the inner cell mass and a fluid-filled, blastocyst cavity known as the blastocoele or the blastocystic cavity.
  • The trophoblast combines with the maternal endometrium to form the placenta in eutherian mammals.
  • Before gastrulation, the cells of the trophoblast become differentiated into two strata.
  • The blastocyst possesses an inner cell mass from which the embryo will develop, and an outer layer of cells, called the trophoblast, which will eventually form the placenta.

• Implantation

  • The zona pellucida degenerates and decomposes, and is replaced by a layer of underlying cells called the trophoblast.
  • The trophoblast will give rise to the placenta after implantation.
  • During implantation, the trophoblast differentiates into two distinct layers: the inner cytotrophoblast, and the outer syncytiotrophoblast.
  • During implantation, extensions of the trophoblast, the syncytiotrophoblasts, embed within the endometrium and form chorionic villi.

• Cleavage of the Zygote

  • However, they quickly become arranged into an outer or peripheral layer, the trophoblast, and an inner cell mass.
  • The trophoblast does not contribute to the formation of the embryo proper; the embryo develops from the inner cell mass .
  • Fluid collects between the trophoblast and the greater part of the inner cell mass, and thus the morula, is converted into the blastodermic vesicle (also called the blastocyst or blastula).
  • The inner cell mass remains in contact with the trophoblast at one pole of the ovum.

• Chorionic Villi and Placental Development

  • During the primary stage (the end of fourth week), the chorionic villi are small, nonvascular, and contain only the trophoblast.
  • During the secondary stage (the fifth week), the villi increase in size and ramify, while the mesoderm grows into them; at this point the villi contain trophoblast and mesoderm.
  • At this point, the villi contain trophoblast, mesoderm, and blood vessels.
  • The outer layer of the blastocyst becomes the trophoblast, which forms the outer layer of the placenta.

• Cleavage, the Blastula Stage, and Gastrulation

  • Here the cells in the blastula arrange themselves in two layers: the inner cell mass and an outer layer called the trophoblast .
  • The trophoblast will contribute to the placenta and nourish the embryo.
  • The rearrangement of the cells in the mammalian blastula to two layers, the inner cell mass and the trophoblast, results in the formation of the blastocyst.

• Sinusoid Development

  • The invasion of endometrial sinusoids by the trophoblast allows maternal blood flow into the trophoblastic lacunae; this forms the uteroplacental blood circulation.

• Fourth Week of Development

  • Trophoblast cells surrounding the embryonic cells proliferate and invade deeper into the uterine lining.

• Early Pregnancy Tests

  • The first of these markers to be discovered, human chorionic gonadotropin (hCG), is produced by the trophoblast cells of the fertilized ovum (blastocyst).