Biology

Difference Between Blastula and Gastrula

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Main Difference

The main difference between Blastula and Gastrula is that Blastula is a hollow ball of cells, whereas Gastrula is a hollow cup-shaped structure with three distinct layers of cells during the embryo development.

Blastula vs. Gastrula

During the process of blastulation, blastula results from the morula. Gastrula formed in result of blastula during the process of gastrulation. The blastula is a single-layered hollow structure. Gastrula is a three-layered hollow structure. The blastula is just like a hollow ball of cells; that’s why cells in it don’t show any movement during its formation. Gastrula cells showed migration during the process of gastrulation when gastrula formed blastula. Blastula consists of 128 cells. Gastrula contains more cells comparatively.

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In blastula, un-differentiated cells are present. In gastrula, differentiated cells are present. The blastula covered with zona pellucida (thick layer to protect the ovum). Gastrula not covered with zona pellucida. In blastula, blastocoel is present. In gastrula, blastopores are present. The blastula is an early embryonic stage. Gastrula is a mature stage of embryonic development that is followed by blastula.

In blastula, the cavity filled with fluid. In gastrula, the cavity filled with blastopores. Blastula comprises of inner cell mass, which leads to embryo blast; the outer most layer, i.e., trophoblast, gives rise to the placenta. Gastrula is a massive movement of cells to form different layers.

In mammals, the blastula also said as “blastocyst.” In gastrula, three germ-layers interact to form organs known as “organogenesis.” Blastula has a single outer layer of cells called “blastoderm.” Gastrula mainly has three germ layers. The blastula is six to thirty-two celled hollow structures — gastrula formed through inward migration of cells of the blastula. The blastula formed when the embryo is not mature. Gastrula further leads to the formation of a mature embryo.

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Comparison Chart

BlastulaGastrula
1st stage after fertilizationThe stage just after the blastula
Layers Present
Zona pellucidaEctoderm, mesoderm, and endoderm
Stages in Embryogenesis
BlastulationGastrulation
Cell Division
No cell divisionCells start differentiation
Blastocoel
Covers mostly volumeCovers less volume
Cell Number
Fewer cells are presentMore cells are present
Cell Differentiation
UndifferentiatedDifferentiated
Results From
ZygoteBlastula

What is Blastula?

The blastula is an early stage of development in the human embryo. The egg of an animal fertilizes with sperm at the fallopian tube in the mother’s body. After the process of fertilization, a zygote is formed lead to a series of cell division via the process of mitosis after stick out in the mother’s uterus. The process known as cleavage started division and produced a solid mass ball of cells is known as “morula.” Cells present in the morula called “blastomeres.” In blastula cells, start to compact and move to the edge of the cell, leaving a fluid-filled space in the center. This fluid-filled cavity surrounding the blastoderm is known as “blastocoel.” An outer single-celled layer is present to cover blastocoel is known as “blastoderm.”

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In mammals, blastula develops into “blastocyst.” It contains an inner mass, which is slightly different from a blastula. The spherical layer of the blastocyst called “trophoblast.” This trophoblast layer further develops into the placenta, which nourishes the growing embryo. Inner cell mass in blastocoel is also known as “embryoblast.” An embryoblast leads to different types of cells. It further helps in organogenesis.

When blastocyst reaches the uterus, it enters the endometrium wall of the uterus for the process known as “implantation.” During the implantation process, blastocyst hatches inside the zona pellucida (a thick transparent membrane surrounds the ovum for protection). The process of implantation completed in 11-12 days after fertilization. Ovum completely implanted in the endometrium wall of the uterus, and then blastula is referred to as an embryo.

What is Gastrula?

Gastrula stage is the stage in which early embryo develops three germ layers, which further helps in organogenesis. Most of the cells that are present on the surface move to a new interior location. This inward movement of the cells is known as “invagination.” These invaginated cells are collocating to the opposite side and converting the embryo into the double-walled cup. Gastrula gives rise to the endoderm wall and mesoderm wall. The exterior cup remains, which gives rise to the ectoderm.

The outermost layer, which is known as ectoderm, differentiates into the brain, skin, spinal cord, and nerves of the embryo. The middle layer mesoderm forms muscles, cartilage, reproductive organs, bones, connective tissue, and skin dermis and teeth dentine. The innermost layer that is ectoderm differentiates into the primitive gut in organisms
in diploblastic organisms; two primary germ layers formed that is ectoderm and endoderm. In triploblastic organisms, three germ layers endoderm, ectoderm, and mesoderm organized in the proper location in an embryo during the gastrulation process.

Blastocoel presents in blastula is eliminated by the invagination of the cells. However, in the hollow cup, a new cavity develops, which is known as “archenteron.” Archenteron forms a future gut of rudiment animals. Opening in the archenteron called “blastopore.”

After the gastrulation process, rapid cell division get starts in the embryo and various organs to form by a process called “organogenesis.” Blastula changes into gastrula; this process known as “gastrulation.” This process is then proceeding by organogenesis. Three germ-layers that produced in gastrula are then ultimately giving rise to organs in mature embryo.

Key Differences

  1. In blastula cells, don’t move, whereas, in gastrulation, cell masses move through morphogenetic movements.
  2. The blastula results from blastulation; on the other hand, gastrula results from gastrulation.
  3. In blastula germ layers are not present; on the flip side in gastrula, three germ layers are present.
  4. The blastula is an early stage of development of an embryo, although gastrula is an embryo at the stage after blastula.
  5. Blastula has fewer cells; rather, gastrula has more cells comparatively.
  6. Blastula shows slow division, while gastrula shows a rapid division of cells.
  7. The blastula stage has undifferentiated cells. However, gastrula contains differentiated cells.
  8. The blastula is spherical shaped, whereas gastrula is cup-shaped.
  9. Morphogenetic cell movement doesn’t observe in blastula, while morphogenetic cell movements observed in gastrula.
  10. In blastula, blastocoel expanded. However, in gastrula, blastocoel becomes shrinks.
  11. Blastula consists of a single-layered structure, whereas gastrula consists of outer as well as the inner layer.
  12. The blastula is also known as pre-embryo; on the other side, gastrula, also known as mature-embryo.
  13. Blastula possesses zona pellucida, while gastrula does not possess zona pellucida.
  14. The blastula is the first stage of embryonic development; on the flip side, gastrula is the mature stage of embryonic development.
  15. The blastula is formed after zygote, whereas the inward migration of differentiated cells forms gastrula.

Conclusion

It concluded that Blastula referred to as pre-embryo, and Gastrula is mature-embryo.

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White

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