Biology Prefixes and Suffixes: Ect- or Ecto-

Spitting Cobra
Spitting Cobra: Snakes and other reptiles are ectotherms and must obtain heat from their external environment. Digital Vision/Getty Images

The prefix ecto- comes from the Greek ektos, which means outside. (Ecto-) means outer, external, out, or outside. Related prefixes include (ex- or exo-).

Words Beginning With (Ecto-)

Ectoantigen (ecto-antigen): An antigen that is located on the surface or exterior of a microbe is known as an ectoantigen. An antigen is any substance that elicits an antibody immune response.

Ectocardia (ecto-cardia): This congenital condition is characterized by displacement of the heart, particularly a heart that is outside of the chest cavity.

Ectocornea (ecto-cornea): The ectocornea is the outer layer of the cornea. The cornea is the clear, protective layer of the eye.

Ectocranial (ecto-cranial): This term describes a position that is external to the skull.

Ectocytic (ecto-cytic): This term means outside of or external to a cell.

Ectoderm (ecto-derm): Ectoderm is the outer germ layer of a developing embryo that forms skin and nervous tissue.

Ectoenzyme (ecto-enzyme): An ectoenzyme is an enzyme that is attached to the outer cell membrane and is secreted externally.

Ectogenesis (ecto-genesis): The development of an embryo outside of the body, in an artificial environment, is the process of ectogenesis.

Ectohormone (ecto-hormone): An ectohormone is a hormone, such as a pheromone, that is excreted from the body into the external environment. These hormones typically alter the behavior of other individuals of the same or different species.

Ectomere (ecto-mere): This term refers to any blastomere (a cell resulting from cell division that occurs after fertilization) that forms the embryonic ectoderm.

Ectomorph (ecto-morph): An individual with a tall, lean, thin body type predominated by tissue derived from the ectoderm is called an ectomorph.

Ectoparasite (ecto-parasite): An ectoparasite a parasite that lives on the outer surface of its host. Examples include fleas, lice, and mites.

Ectopia (ecto-pia): The abnormal displacement of an organ or body part outside of its proper location is known as ectopia. An example is ectopia cordis, a congenital condition where the heart sits outside of the chest cavity.

Ectopic (ecto-pic): Anything that occurs out of place or in an abnormal position is called ectopic. In an ectopic pregnancy, a fertilized egg attaches to a fallopian tube wall or other surface that is outside of the uterus.

Ectophyte (ecto-phyte): An ectophyte is a parasitic plant that lives on the outer surface of its host.

Ectoplasm (ecto-plasm): The outer area of the cytoplasm in some cells, such as protozoans, is known as ectoplasm.

Ectoprotein (ecto-protein): Also called an exoprotein, an ectoprotein is the term for an extracellular protein.

Ectorhinal (ecto-rhinal): This term refers to the exterior of the nose.

Ectosarc (ecto-sarc): The ectoplasm of a protozoan, such as an amoeba, is called the ectosarc.

Ectosome (ecto-some): An ectosome, also called an exosome, is an extracelluar vesicle that is often involved in cell-to-cell communication. These vesicles containing proteins, RNA, and other signaling molecules bud off from the cell membrane.

Ectotherm (ecto-therm): An ectotherm is an organism (like a reptile) that uses external heat to regulate its body temperature.

Ectotrophic (ecto-trophic): This term describes organisms that grow and obtain nutrients from the surface of tree roots, such as mycorrhiza fungi.

Ectozoon (ecto-zoon): An ectozoon is an ectoparasite living on the surface of its host.