Müllerian

Müllerian is an adjective derived from the German surname Müller (often written with the umlaut, Müller). In scientific usage, the term appears in several eponymous concepts named after researchers with that name, particularly in anatomy and evolutionary biology.

One of the best-known uses is Müllerian ducts, also called paramesonephric ducts. These embryonic ducts in females develop to form much of the internal reproductive tract, including the fallopian tubes, uterus, and the upper portion of the vagina. In typical male development, anti-Müllerian hormone produced by fetal Sertoli cells causes regression of these ducts. Abnormal persistence or regression of the Müllerian ducts can lead to reproductive tract anomalies.

Müllerian agenesis, also known as Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome, is a congenital condition in which Müllerian ducts fail to develop properly. Individuals with this condition usually have normal ovaries and external genitalia but absent or underdeveloped uterus and upper vagina.

In evolutionary biology, Müllerian mimicry refers to a phenomenon where two or more unpalatable or harmful species resemble each other, thereby reinforcing avoidance by predators. The concept was described by Fritz Müller in the 19th century and is distinguished from Batesian mimicry, in which a harmless species imitates a harmful one.

The term may also appear in other, less common eponyms derived from scientists named Müller. English usage sometimes drops the umlaut, producing Mullerian, though Müllerian remains standard in scientific literature.