Saturdays are perfect days for affix surprises. Surprise—we’re talking about words for the prefixes ECTO-, ENDO-, and MESO- today!
Certain prefixes tend to appear together, especially when they easily connect to other roots to facilitate the creation of scientific terms. The prefixes ECTO-, ENDO-, and MESO- definitely fall into this category:
ECTO- is a prefix meaning outside or external.
ENDO- is a prefix meaning inside or internal.
MESO- is a prefix meaning middle.
One well-known application of these prefixes entails the use of the the root MORPH- meaning shape to describe somatotypes or body types:
ectomorph (noun) - a person with a lean or slender body; someone with low body fat and metabolism
endomorph (noun) - a person with a round or wide body with an excess of body fat and a high metabolism
mesomorph (noun) - a person with an athletic build, able to gain muscle and lose fat easily
Anyone with a background in biology should be familiar with the combination of these prefixes with the root DERM- meaning skin to describe the three primary germ layers formed during embryonic development.
ectoderm (noun) - the outermost layer of embryonic development, which includes the nervous system and skin
endoderm (noun) - the innermost layer of embryonic development, which includes the digestive and respiratory systems
mesoderm (noun) - the middle layer of embryonic development, which includes muscles, bones, and the circulatory system
ECTO- and ENDO- appear in many more contrasting terms, including those based on the roots THERM- (to heat or warm)…
ectotherm (noun) - an organism that is dependent on external sources of body heat; a cold-blooded animal
endotherm (noun) - an organism that generates and maintains a stable internal body temperature independent of external conditions; a warm-blooded animal
… and PLASM- (growth or creation):
ectoplasm (noun) - the watery outer part of a cell’s cytoplasm; an immaterial or viscous substance that secretes off spirits or accompanies ghostly phenomena
endoplasm (noun) - the dense inner part of a cell’s cytoplasm
MESO- also pops up in biology and medical terms but also contributes to more general words:
Mesoamerica (noun) - the combined territories of of Mexico and Central America; middle America
mesosphere (noun) - the layer of Earth’s atmosphere located between the stratosphere and the thermosphere, roughly 31 to 50 miles above the surface
“I am an invisible man. No I am not a spook like those who haunted Edgar Allen Poe: Nor am I one of your Hollywood movie ectoplasms. I am a man of substance, of flesh and bone, fiber and liquids, and I might even be said to possess a mind. I am invisible, simply because people refuse to see me.” —Ralph Ellison