inner cell mass

Examples of inner cell mass in the following topics:

• 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.
  • On the deep surface of the inner cell mass, a layer of flattened cells, called the endoderm, is differentiated and quickly assumes the form of a small sac, called the yolk sac.
  • This layer is derived from the inner cell mass and lies in opposition to the endoderm.
  • 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.

• Cleavage of the Zygote

  • However, they quickly become arranged into an outer or peripheral layer, the trophoblast, and an inner cell mass.
  • The inner cell mass remains in contact with the trophoblast, however, at one pole of the ovum.
  • Monozygotic twins can also develop from two inner cell masses.
  • A rare occurrence is the division of a single inner cells mass giving rise to twins.
  • However, if one inner cell mass divides incompletely, the result is conjoined twins.

• Bilaminar Embryonic Disc Development

  • The floor of the amniotic cavity is formed by the embryonic disc, which is composed of a layer of prismatic cells and the embryonic ectoderm.
  • It is derived from the inner cell mass and lies adjacent to the endoderm.
  • The epiblast layer is derived from the inner cell mass.
  • By the blastocyst stage, the embryo has become a hollow ball of cells with the inner cell mass (embryoblast) off to one side, while the blastocystic cavity completes the remainder of the sphere.
  • Simultaneously, morphological changes ocur in the embryoblast that result in the formation of a flat, almost circular bilaminar plate of cells--the embryonic disk--which includes the epiblast and the hypoblast.

• Cleavage, the Blastula Stage, and Gastrulation

  • Mammals at this stage form a structure called the blastocyst, characterized by an inner cell mass that is distinct from the surrounding blastula.
  • Here the cells in the blastula arrange themselves in two layers: the inner cell mass and an outer layer called the trophoblast .
  • The inner cell mass is also known as the embryoblast; this mass of cells will go on to form the embryo.
  • At this stage of development, the inner cell mass consists of embryonic stem cells that will differentiate into the different cell types needed by the organism.
  • 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.

• Cellular Differentiation

  • Three basic categories of cells make up the mammalian body: germ cells, somatic cells, and stem cells.
  • The blastocyst has an outer layer of cells, and inside this hollow sphere, there is a cluster of cells called the inner cell mass.
  • The cells of the inner cell mass go on to form virtually all of the tissues of the human body.
  • Although the cells of the inner cell mass can form virtually every type of cell found in the human body, they cannot form an organism.
  • Mesenchymal stem cells (adult stem cells) from the bone marrow that give rise to stromal cells, fat cells, and types of bone cells;

• Amnion Development

  • The amnion is a closed sac appearing in the inner cell mass as a cavity.
  • This cavity is roofed in by a single stratum of flattened, ectodermal cells called the amniotic ectoderm.
  • This fluid increases in quantity, causing the amnion to expand and ultimately to adhere to the inner surface of the chorion so that the extra-embryonic part of the coelom is obliterated.

• Gene Expression in Stem Cells

  • In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues.
  • Stem cells can now be artificially grown and differentiated into specialized cell types with characteristics consistent with muscle or nerve cells through cell culture.
  • In one, the daughter cells are initially equivalent but a difference is induced by signaling between the cells, from surrounding cells, or from the precursor cell.
  • Stem cells are indicated by (A), progenitor cells by (B), and differentiated cells by (C).
  • Pluripotent, embryonic stem cells originate as inner cell mass (ICM) cells within a blastocyst.

• Tissue Development

  • After about three days, the zygote forms a solid mass of cells by mitotic division, called a morula.
  • This then becomes a blastocyst, consisting of an outer layer called a trophoblast, and an inner cell mass called the embryoblast.
  • The inner cell mass initially has two layers: the hypoblast and epiblast.
  • Cells migrating inward along the primitive gut form the inner layer of the gastrula, which develops into the endoderm.
  • Image illustrates the types of cells produced by the endoderm (inner germ layer) of the developing embryo.

• Muscle Development

  • Body builders enhance the natural developmental processes of myoblast muscle fusion and dedifferentiation into myosatellites to dramatically increase myosatellite mass, and thus muscle size and weight.
  • The cells of the inner cell mass (embryoblast), which are known as human embryonic stem cells (hESCs), will differentiate to form four structures: the amnion, the yolk sac, the allantois, and the embryo itself.
  • A myoblast is a type of embryonic progenitor cell that differentiates to give rise to muscle cells.
  • A myocyte (also known as a muscle cell or muscle fiber) is the type of cell found in muscle tissue.
  • Satellite cells are located between the basement membrane and sarcolemma (cell membrane) of individual muscle fibers.

• Muscularis

  • The muscularis externa consists of an inner circular layer and a longitudinal outer muscular layer.
  • Activity is initiated by the pacemaker cells (interstitial cells of Cajal).
  • Occasionally in the large intestine (two to three times a day), there will be mass contraction of certain segments, moving a lot of feces along.
  • The pylorus of the stomach has a thickened portion of the inner circular layer: the pyloric sphincter.
  • This is the inner oblique layer, and helps churn the chyme in the stomach.