What is formed during gastrulation?
During gastrulation, the three primary germ layers of an embryo are formed. These germ layers are known as the ectoderm, mesoderm, and endoderm.
To understand how these germ layers are formed during gastrulation, we need to look at the early stages of embryonic development. The process of gastrulation occurs after the stage known as the blastula. The blastula is a hollow ball of cells, with a fluid-filled cavity called the blastocoel.
Gastrulation involves a series of intricate cellular movements and rearrangements that result in the formation of the three germ layers. Here's a simplified step-by-step explanation of gastrulation:
1. Intion: A small region on the surface of the blastula begins to fold inward, forming a structure called the blastopore. This process is known as intion. The intion creates an opening into the developing embryo.
2. Formation of the endoderm: As the intion continues, cells from the surface of the blastula move inward through the blastopore and form a new layer of cells inside the embryo. This new layer is called the endoderm. The endoderm gives rise to the inner linings of various organs, such as the digestive tract and respiratory system.
3. Formation of the mesoderm: As the endoderm is being formed, other cells from the surface of the blastula migrate between the endoderm and the outer layer (also known as the ectoderm), forming a middle layer called the mesoderm. The mesoderm gives rise to various tissues and structures, including muscles, bones, connective tissues, and circulatory system.
4. Formation of the ectoderm: The remaining outer layer of cells that did not migrate inward becomes the ectoderm. The ectoderm gives rise to the outermost layer of the embryo, which eventually differentiates into the skin, nervous system, and other related structures.
So, in summary, during gastrulation, the three germ layers (ectoderm, mesoderm, and endoderm) are formed, which eventually give rise to all the tissues and organs of the developing embryo.