Webster's New World Medical Dictionary

economy-class syndrome
See 
deep vein
thrombosis.
ecstasy 1
A state of rapture and trancelike ela-
tion.
2
A street name for 3, 4-methylene-
dioxymethamphetamine (MDMA), a synthetic,
mind-altering drug with hallucinogenic and
amphetamine-like properties—other street names
include “Adam” and “XTC.” Its chemical structure
is similar to two other synthetic drugs, MDA and
methamphetamine. See also 
designer drug.
ECT
Electroconvulsive therapy.
ectoderm
The outermost of the three primary
germ cell layers (the other two being the mesoderm
and endoderm) that make up a very young embryo.
The ectoderm differentiates (specializes) to give
rise to many important tissues and structures,
including the outer layer of the skin and its
appendages (such as the sweat glands, hair, and
nails), the teeth, the lens of the eye, parts of the
inner ear, the nerves, the brain, and the spinal cord.
Stem cell research has shown that some cells within
ectodermal structures retain their ability to differ-
entiate into other tissues. For example, some cells in
the brain (ectoderm) can become bone marrow
(mesoderm). See also 
differentiation; embryo;
endoderm; mesoderm.
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 dys-
plasia is most common; because it is an X-linked
trait, it mainly affects males. There is also an auto-
somal dominant form that affects both males and
females. The term ectodermal dysplasia refers to the
abnormal development (dysplasia) of structures
derived from one of the germ cell layers in the
embryo (ectoderm).