Ektodermiin

Ektodermiin (ectoderm) refers to the outermost of the three primary germ layers formed during early embryonic development. It arises during gastrulation from epiblast cells that remain on the embryo’s exterior, giving rise to two main subdivisions: neuroectoderm and surface ectoderm. The neuroectoderm folds to form the neural tube, which becomes the central nervous system, while neural crest cells migrate to form many structures, including parts of the peripheral nervous system and various craniofacial tissues.

Major derivatives of the ectoderm include the epidermis and its appendages (hair, nails, sweat glands), the lens and corneal epithelium of the eye, the olfactory epithelium and other sensory placodes, and the enamel of teeth. Craniofacial structures such as certain bones and cartilage originate from neural crest cells derived from the ectoderm, and the anterior pituitary gland (via Rathke’s pouch) also has ectodermal origins.

Clinical relevance: Disorders of ectodermal development, such as ectodermal dysplasias, affect structures derived from this germ layer, including hair, teeth, nails, and glands. Abnormal neurulation can lead to neural tube defects, reflecting the essential role of ectodermal development in forming the nervous system and related tissues. Overall, the ectoderm is fundamental to forming many tissues that protect the body and enable sensory perception and neural function.