Germ layers

Germ layers are the three primary layers of cells that form in the early development of an embryo. These layers are known as the ectoderm, mesoderm, and endoderm. Each layer gives rise to specific tissues and organ systems in the developing fetus.

Ectoderm

The ectoderm is the outermost germ layer. It forms from the embryo's epiblast and gives rise to the nervous system, skin, and hair. The ectoderm also forms the lining of mouth, anus, nostrils, sweat glands, hair and nails.

Mesoderm

The mesoderm is the middle germ layer. It forms various types of muscle, bone, cartilage, and the circulatory system. The mesoderm also forms the urogenital system, which includes the kidneys and reproductive organs.

Endoderm

The endoderm is the innermost germ layer. It forms the lining of the digestive tract, respiratory system, and several glandular organs, including the liver and pancreas.

Development

The formation of germ layers is a step in the process of organogenesis, the formation of organs. This process begins with gastrulation, a phase of embryonic development in which the single-layered blastula is reorganized into a trilaminar (three-layered) structure known as the gastrula.

See also

• Embryogenesis
• Gastrulation
• Organogenesis

References

Germ layers Resources
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