Science, Tech, Math › Science End- or Endo- Biology Prefixes and Suffixes Share Flipboard Email Print Didier Descouens/Wikimedia Commons/ CC BY-SA 3.0 Science Biology Basics Cell Biology Genetics Organisms Anatomy Physiology Botany Ecology Chemistry Physics Geology Astronomy Weather & Climate By Regina Bailey Biology Expert B.A., Biology, Emory University A.S., Nursing, Chattahoochee Technical College Regina Bailey is a board-certified registered nurse, science writer and educator. Her work has been featured in "Kaplan AP Biology" and "The Internet for Cellular and Molecular Biologists." our editorial process Regina Bailey Updated May 16, 2019 The prefix (end- or endo-) means within, inside or internal. Examples Endobiotic (endo-biotic) - referring to a parasite or symbiotic organism that lives within the tissues of its host. Endocardium (endo-cardium) - inner membrane lining of the heart that also covers heart valves and is continuous with the inner lining of blood vessels. Endocarp (endo-carp) - the hard inner layer of pericarp that forms the pit of ripened fruit. Endocrine (endo-crine) - refers to the secretion of a substance internally. It also refers to glands of the endocrine system that secrete hormones directly into the blood. Endocytosis (endo-cytosis) - transport of substances into a cell. Endoderm (endo-derm) - inner germ layer of a developing embryo that forms the lining of the digestive and respiratory tracts. Endoenzyme (endo-enzyme) - an enzyme that acts internally to a cell. Endogamy (endo-gamy) - internal fertilization between flowers of the same plant. Endogenous (endo-genous) - produced, synthesized or caused by factors within an organism. Endolymph (endo-lymph) - the fluid contained within the membranous labyrinth of the inner ear. Endometrium (endo-metrium) - inner mucous membrane layer of the uterus. Endomitosis (endo-mitosis) - a form of internal mitosis in which chromosomes replicate, however the division of the nucleus and cytokinesis do not occur. It is a form of endoreduplication. Endomixis (endo-mixis) - reorganization of the nucleus that occurs within the cell in some protozoans. Endomorph (endo-morph) - an individual with a heavy body type predominated by tissue derived from the endoderm. Endophyte (endo-phyte) - a plant parasite or other organism that lives within a plant. Endoplasm (endo-plasm) - the inner portion of the cytoplasm in some cells such as protozoans. Endorphin (endo-dorphin) - a hormone produced within an organism that acts as a neurotransmitter to reduce the perception of pain. Endoskeleton (endo-skeleton) - an organism's internal skeleton. Endosperm (endo-sperm) - tissue within the seed of an angiosperm that nourishes the developing plant embryo. Endospore (endo-spore) - an inner wall of a plant spore or pollen grain. It also refers to a non-reproductive spore produced by some bacteria and algae. Endothelium (endo-thelium) - thin layer of epithelial cells that form the inner lining of blood vessels, lymphatic vessels and heart cavities. Endotherm (endo-therm) - an organism that generates heat internally to maintain constant body temperature.