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The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). [1] It emerges and originates from the outer layer of germ cells.
2.3.3 Body cavities. ... Organs; Systems; ... This is a list of cells in humans derived from the three embryonic germ layers – ectoderm, mesoderm, and endoderm ...
Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). [ 1 ] Cells migrating inward along the archenteron form the inner layer of the gastrula , which develops into the endoderm.
The ectoderm generates the outer layer of the embryo, and it forms from the embryo's epiblast. [13] The ectoderm develops into the surface ectoderm, neural crest, and the neural tube. [14] The surface ectoderm develops into: epidermis, hair, nails, lens of the eye, sebaceous glands, cornea, tooth enamel, the epithelium of the mouth and nose.
The ectoderm divides to form a flat layer of cells on the surface known as the periderm. Further division forms the individual layers of the epidermis. The mesenchyme that will form the dermis is derived from three sources: The mesenchyme that forms the dermis in the limbs and body wall derives from the lateral plate mesoderm
The endoderm is the inner most germ layer of the embryo which gives rise to gastrointestinal and respiratory organs by forming epithelial linings and organs such as the liver, lungs, and pancreas. [5] The mesoderm or middle germ layer of the embryo will form the blood, heart, kidney, muscles, and connective tissues. [5]
Human organs and organ systems develop in a process known as organogenesis. This begins in the third week of embryonic development, when the gastrula forms three distinct germ layers, the ectoderm, mesoderm and endoderm. The ectoderm will eventually develop into the outer layer of skin and nervous system.
During gastrulation, some of the cells migrating inward to form the endoderm form an additional layer between the endoderm and the ectoderm. A theory suggests that this key innovation evolved hundreds of millions of years ago and led to the evolution of nearly all large, complex animals.