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Blastula vs. Gastrula: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Updated on October 28, 2023
The blastula is an early-stage embryonic structure formed by a hollow ball of cells, while the gastrula is a subsequent stage where primary germ layers begin to differentiate.

Key Differences

The blastula is a stage in embryonic development characterized by a single-layered sphere of cells surrounding a fluid-filled cavity. The gastrula follows the blastula and introduces a more complex structure through the invagination or infolding of its cells.
In the process of embryogenesis, after the fertilized egg undergoes several rounds of cell division, it forms the blastula. The gastrula emerges when specific cells in the blastula start to move inward, creating a multilayered structure.
The blastula essentially represents a simple stage of embryonic growth, mainly focusing on rapid cell division. In contrast, the gastrula marks the beginning of differentiation, where the embryo starts to form distinct germ layers that will later develop into various tissues and organs.
Within the blastula, there's a noticeable lack of specialized structures or cells. But in the gastrula, one can identify the ectoderm, mesoderm, and endoderm, which are the foundational layers for all organs and tissues in an organism.
To summarize, the blastula can be thought of as a preliminary canvas, a simple and rapid multiplication of cells. The gastrula, however, paints a clearer picture of the organism's future, laying down the primary architectural groundwork through germ layers.

Comparison Chart

Stage in Development

Early embryonic stage
Follows the blastula stage

Cellular Complexity

Single-layered sphere of cells
Multilayered structure with germ layers

Germ Layers Present

No germ layers
Contains ectoderm, mesoderm, and endoderm


Focuses on rapid cell division
Begins differentiation into various tissues and organsa

Structural Appearance

Hollow ball of cells
Cells start to move inward, creating a distinct shape

Blastula and Gastrula Definitions


An early embryonic form consisting of a hollow ball of cells.
The embryo first takes the shape of a blastula before proceeding to more complex stages.


An embryonic stage following the blastula, marked by cell migration and germ layer formation.
The gastrula's formation signifies the beginning of cellular differentiation in the embryo.


A fluid-filled spherical layer of cells in early embryonic growth.
The blastula's hollow center is evident under the microscope.


The stage where cells start to move inward, forming a distinct multilayered structure.
The cellular movements in the gastrula lay the foundation for future organ and tissue development.


The structure preceding the gastrula in the developmental sequence.
After the blastula stage, the embryo transforms into the gastrula.


An embryo undergoing the process of gastrulation.
The invagination of cells in the gastrula leads to the formation of various body structures.


A simple, undifferentiated embryonic stage.
The blastula lacks the germ layers that are evident in subsequent developmental stages.


The developmental phase where primary germ layers emerge.
During the gastrula stage, the ectoderm, mesoderm, and endoderm become distinguishable.


A stage in embryogenesis characterized by rapid cell division.
Following fertilization, the cell divides multiple times to form the blastula.


A more advanced embryonic form than the blastula.
The transition from the blastula to the gastrula indicates an increase in embryonic complexity.


An embryo at the stage following the blastula, after the movement of cells results in the formation of the three germ layers, ectoderm, mesoderm, and endoderm.


What is a blastula?

The blastula is an early-stage embryonic structure consisting of a hollow ball of cells.

Why is the blastula stage essential for embryonic development?

The blastula provides a foundation for subsequent developmental stages, like the gastrula.

How is gastrulation triggered in the blastula?

Gastrulation is initiated by various molecular and cellular cues that cause cells to change shape and move.

Does the blastula directly develop into the gastrula?

Yes, the blastula undergoes gastrulation to transform into the gastrula.

What process introduces the gastrula's multilayered structure?

The process of gastrulation involves cells of the blastula moving inward to form the gastrula's layers.

Are there germ layers present in the blastula?

No, the blastula lacks germ layers; they begin to form in the gastrula stage.

What are the main germ layers in the gastrula?

The gastrula has three primary germ layers: ectoderm, mesoderm, and endoderm.

What comes after the gastrula in embryonic development?

After the gastrula, the embryo continues differentiating, leading to organogenesis and further developmental stages.

How does the gastrula contribute to an organism's development?

The gastrula establishes the primary germ layers, which differentiate into various tissues and organs.

How long does an embryo remain in the blastula phase?

The duration in the blastula stage varies across species and depends on several developmental factors.

Is the blastula's hollow center significant?

Yes, the blastula's cavity, or blastocoel, plays a role in cellular movements during gastrulation.

Are there other names for the blastula in different organisms?

In mammals, the structure comparable to the blastula is often termed the "blastocyst."

Why is the gastrula stage named so?

The term "gastrula" derives from the Greek word for "stomach," reflecting the stage's pouch-like appearance.

What's the relationship between the blastula and gastrula in the context of evolutionary biology?

Both stages are foundational in animal development, and their presence in diverse taxa suggests a shared evolutionary ancestry.

How does the gastrula follow the blastula in development?

The gastrula emerges from the blastula when cells begin to move inward, creating a multilayered structure.

Is the blastula a complex structure?

No, the blastula is a simple, single-layered sphere of cells.

What's the significance of the gastrula stage?

The gastrula marks the onset of cellular differentiation, leading to the formation of organs and tissues.

Is the blastula unique to specific organisms?

While the term "blastula" is commonly used in relation to many animals, its exact structure can vary across species.

Does the gastrula exist in all animals?

Most multicellular animals have a gastrula stage, but its specifics can differ among taxa.

Which germ layer in the gastrula gives rise to the skin?

The ectoderm, one of the gastrula's germ layers, develops into the skin and nervous system.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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