Gastrulation facts for kids

This picture shows how a simple ball of cells (1) changes into a gastrula (2) during gastrulation. Some orange cells (ectoderm) move inside to form the red layer (endoderm).

Gastrulation is a very important step early in the development of most animal embryos. An embryo is a baby animal in its earliest stages, before it's born or hatched. During gastrulation, the embryo changes its shape a lot as its cells move around and rearrange themselves.

This process is different for various types of animals. After gastrulation comes organogenesis, which is when all the different organs, like the heart or brain, start to form from the new cell layers.

The gastrula is what the embryo is called during gastrulation. It's like a tiny, double-layered ball of cells. During this stage, some cells from the outer layer of the embryo move inwards. These inward-moving cells create an inner layer called the endoderm. In many animals, another layer forms in the middle, called the mesoderm. This mesoderm sits between the inner endoderm and the outer ectoderm.

Germ Layers: The Body's Building Blocks

Animals are built from different layers of cells called germ layers. The simplest animals, like sponges, have only one main layer of cells. Animals like Cnidaria (jellyfish and corals) and ctenophores (comb jellies) are a bit more complex. They have two germ layers: the endoderm and the ectoderm.

All more complex animals, from flatworms to humans, have three germ layers: the ectoderm, endoderm, and mesoderm.

How Germ Layers Form and What They Become

The main goal of gastrulation is to put these three important embryonic germ layers in the right places. These layers are like the basic building blocks that will later develop into all the different parts and systems of an animal's body.

• The ectoderm is the outer layer. It develops into your skin, hair, nails, and the lining of your nose, mouth, and bottom. It also forms the lens and retina of your eyes, and your entire nervous system, including your brain and spinal cord.
• The endoderm is the inner layer. It develops into the inner linings of your digestive system (like your stomach and intestines) and your respiratory system (like your lungs). It also forms many important glands, such as your liver and pancreas.
• The mesoderm is the middle layer. This layer is super important because it forms your muscles, bones, blood, and the systems that help you get rid of waste. The development of the mesoderm was a big step in evolution, allowing for the growth of almost all large, complex animals. It also led to the formation of a coelom, which is a fluid-filled space inside the body. Organs inside this space can move, grow, and develop without being squished by the body wall, and the fluid protects them from bumps and shocks.

Related Topics

• Cellular differentiation (how cells become specialized)

Images for kids

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  This diagram shows how cells can change their shape and move during development, like when they form the mesoderm.

See also

In Spanish: Gastrulación para niños