organ subunit FMA distinguishes segment from zone by whether the fiat boundaries are fixed/anchored (segments) or floating (zone). It's not completely clear how to apply this distinction Organ region with one or more anchored fiat boundaries. Examples: artery, trunk of nerve, cervical part of esophagus, pelvic part of vagina, horn of thyroid cartilage, anterior segment of eyeball. A part of an organ that constitutes a distinct modular sub-unit. In some cases, the organ may also contain other sub-units of identical or similar types, in other cases this may be a distinct entity. organ segment segment of organ FMA:86140 uberon Organ region with one or more fixed or anchored fiat boundaries. Examples: artery, trunk of nerve, cervical part of esophagus, pelvic part of vagina, horn of thyroid cartilage, anterior segment of eyebal. UBERON:0000063 organ region with fixed fiat boundary organ part