any of six small muscles that control the horizontal, vertical, and rotating movements of the eyeball.
noun, Biochemistry. 1. . extrinsic factor n. See vitamin B12.
- Extrinsic incubation period
extrinsic incubation period n. The interval between the acquisition of an infectious agent by a vector and the vector’s ability to transmit the agent to other susceptible vertebrate hosts.
- Extrinsic sphincter
extrinsic sphincter n. A sphincter formed by circular muscular fibers extraneous to the organ.
1. variant of (used to contrast with intro-, ): extrovert. word-forming element meaning “outwards,” a variant of extra- by influence of intro-. extro- pref. Variant of extra-.