Germ layers
Germ layers
Germ layers (pronunciation: /dʒɜːm leɪərz/) are the primary layers of cells that form during embryogenesis, which later differentiate into specific tissues and organs in an organism. The term "germ" in germ layers is derived from the German word "Keim", which means seed or nucleus.
Etymology
The term "germ layer" was first used in the mid-19th century by the German biologist Robert Remak, who was studying the embryonic development of chicken eggs. The term "germ" refers to the initial stage of something, while "layer" refers to the stratified arrangement of these initial cells.
Types of Germ Layers
There are three types of germ layers:
- Ectoderm: The outermost layer, which gives rise to the nervous system, skin, and related structures.
- Mesoderm: The middle layer, which forms the muscles, bones, circulatory system, and other internal organs.
- Endoderm: The innermost layer, which forms the digestive tract, respiratory system, and other internal organs.
Each of these layers has a unique role in the development of the organism and is essential for the formation of different tissues and organs.
Related Terms
- Embryogenesis: The process by which the embryo forms and develops.
- Differentiation: The process by which cells become specialized in structure and function.
- Organogenesis: The process of organ formation that takes place during the development of an organism.
See Also
External links
- Medical encyclopedia article on Germ layers
- Wikipedia's article - Germ layers
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