Source:http://linkedlifedata.com/resource/umls/id/C0504611
UWDA: Organ part, which is countable and consists of two or more organ components; (is divisible into organ components); is demarcated from other subdivisions of the same organ by one or more anatomical lines, anatomical surfaces or topographical references; connected to other subdivisions of the same organ, it constitutes an organ. Examples: right atrium, mitral valve, left lobe of liver, neck of femur, short head of biceps, arch of aorta.