Difference Between Blastula and Gastrula (With Table)

The stages of formation of blastula are called blastulation, and that of a gastrula is called gastrulation. These stages come under the process of embryogenesis. These are the early stages of the formation of an embryo. Before them comes fertilization, which is fertilizing of the egg. After gastrulation comes organogenesis, which is the formation of the organs of an animal’s body.

Blastula vs Gastrula

The difference between blastula and gastrula is that these are two different stages of the same process. The blastula is formed right after fertilization, whereas the gastrula is formed after the blastula. The embryo at the time of blastulation is pre-mature. Whereas at the time of gastrulation, the embryo is matured.

The blastula is usually defined as a hollow sphere of cells. It is formed after the stage of fertilization. It is produced when an embryo goes through a repeated cleavage of a fertilized egg. This stage is called blastulation. It usually encloses a liquid cavity known as blastocoel, by forming a protective layer over it known as blastoderm. The liquid cavity blastocoel contains some components like proteins, amino acids, sugar, etc.

The gastrula is an early multicellular embryo made up of three germinal layers. It is developed from the blastula, and this stage is called gastrulation. It consists of three germinal layers, i.e. ectoderm, mesoderm and endoderm. Their layers are responsible for forming various parts of the animal body later. After the formation of the gastrula, the liquid cavity blastocoel is eliminated, and another cavity is created, which is called endoderm.

Comparison Table Between Blastula and Gastrula

Parameters of comparisonBlastulaGastrula
DefinitionBlastula can be described as a hollow sphere of cells.Gastrula is an early multicellular embryo made up of three germinal layers.
StagesThe second stage in the process of embryogenesis.The third stage in the process of embryogenesis.
Process nameBlastulationGastrulation
Number of cellsLess than the gastrula.More than the blastula.
EmbryoPrematureMature
Germ layerNoneThree layers, i.e., the ectoderm, the mesoderm, and the endoderm.

What is Blastula?

Blastula can be described as a hollow sphere of cells. The word blastula is derived from the Greek word “blastos,” meaning sprout. It is produced due to the repeated cleavage of the fertilized egg during an embryo’s early development. This stage is known as blastulation. It is one of the stages in embryogenesis, which comes after the fertilization of the egg.

Blastula encloses a fluid cavity known as blastocoel by forming a protective layer over it known as blastoderm. The fluid cavity blastocoel contains essential components such as proteins, amino acids, sugar, ions, etc.

After the blastulation stage comes the gastrulation stage, which further develops the embryo. At the time of blastulation, the embryo is pre-mature. in mammals, including humans, the blastula is often called the blastocyst, which contains an embryoblast that eventually defines the fetus’s structure.

What is Gastrula?

Gastrula is an early multicellular embryo made up of three germinal layers. It is formed after blastula, and this stage is known as gastrulation. From gastrula, later the organs of the fetus are developed, and that stage is called organogenesis.

The animal body is made up of a massive number of issues. These tissues are made from three different embryonic cell layers. These layers are the ectoderm: the outermost layer, mesoderm: the middle layer, and the endoderm: the innermost layer. Gastrulation reshuffles the blastula cells into these three layers. Later these layers help in the formation of various organs of the animal body.

The ectoderm layer is responsible for forming the outer parts of the animal body like skin, sense organs, etc. In contrast, mesoderm helps in forming the animal’s musculature, excretory, and reproductive system.
After the gastrula formation, the fluid cavity blastocoel is eliminated, and a new cavity is formed known as endoderm. Endoderm later forms the digestive organs and glands. Gastrula also converts the spherical embryo made up of blastula into a double-walled cup.

During gastrulation, the embryo is matured. Gastrula is made up of more number of cells than blastula.

Main Differences Between Blastula and Gastrula

  1. Gastrulation and blastulation are two different stages in which the blastula is formed first and then the gastrula.
  2. The blastula is defined as the hollow sphere of cells. At the same time, gastrula is determined as the early multicellular embryo made up of three different germinal layers.
  3. The process of formation of the blastula is called blastulation. In comparison, the process of formation of gastrula is called gastrulation.
  4. There are three different germ layers in the gastrula, i.e. the ectoderm, the mesoderm, and the endoderm. In contrast, there is no such germ layer present in the blastula.
  5. Gastrula has more number of cells as compared to blastula.
  6. At the time of blastulation, the embryo is pre-mature. Whereas in the case of gastrulation, the embryo is matured.

Conclusion

The blastula is often defined as the hollow sphere of cells, and its formation process is called blastulation. Whereas gastrula is an early multicellular embryo made up of various germ layers, its formation process is known as gastrulation. These two stages come under embryogenesis along with the other two phases, i.e., fertilization and organogenesis.

The blastula is formed due to the repeated cleavage of the fertilized egg during an embryo’s early development. It encloses a liquid fluid cavity known as blastocoel by developing a protective layer above it called blastoderm. This cavity consists of the various components which are necessary for the development of the Embryo.

Gastrula, on the other hand, is formed after the blastula. It is made up of three germinal layers, i.e., the ectoderm, the mesoderm, and the endoderm. These three layers are responsible for further organ development of the fetus.

For example, the ectoderm layer is responsible for forming the outer body parts of the animal body, such as the sense organs, skin, etc. In contrast, the endoderm layer is accountable for the the formation of the digestive organs. Also, the mesoderm layer helps in the formation of animal musculature, excretory, and reproductive system.

At the time of blastulation, the Embryo is premature. However, it matures as soon as it reaches the gastrulation stage.

References

  1. https://www.sciencedirect.com/science/article/pii/0012160673900493
  2. https://rupress.org/jcb/article-abstract/32/1/121/16894
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