Ectoderm: One of the three primary germ cell layers (the other two being the mesoderm and endoderm) that make up the very early embryo. The ectoderm is the outermost of the three layers. It differentiates to give rise to many important tissues and structures including the outer layer of the skin and its appendages (the sweat glands, hair, and nails), the teeth, the lens of the eye, parts of the inner ear, the nerves, brain, and spinal cord. This much is classic human embryology.
Stem cell research, however, has shown that some cells within ectodermal structures retain their ability to differentiate into other tissues. For example, some cells in brain (ectoderm) can become bone marrow (mesoderm).
Ectodermal: Pertaining to the ectoderm or to tissues derived from the ectoderm, one of the three primary germ cell layers that make up the very early embryo. The ectoderm is the outermost of the three layers.
- Ectodermal dysplasia
Ectodermal dysplasia: A genetic disorder in which the skin and associated structures (the hair, nails, teeth, and sweat glands) develop abnormally. X-linked anhidrotic (nonsweating) ectodermal dysplasia is most common; because it is an X-linked trait, it mainly affects males. There is also an autosomal dominant form that affects both males and females. The term ectodermal […]
Ectomy: The surgical removal of something. For example, a lumpectomy is the surgical removal of a lump, a tonsillectomy is the removal of the tonsils, and an appendectomy is removal of the appendix.
Ectoparasite: A parasite that lives on or in the skin but not within the body. Fleas and lice are ectoparasites. Infestation with an ectoparasite is called an ectoparasitosis.
Ectoparasitosis: Infestation with an ectoparasite, a parasite that lives on or in the skin. The four major ectoparasitoses are pediculosis, scabies, cutaneous larva migrans and tungiasis (sand-flea disease).