part of endocrine system endocrine gland Endocrine glands are glands of the endocrine system that secrete their products directly into the circulatory system rather than through a duct. FMA:9602 MESH:D004702 NCIT:C1270 UMLS:C0014133 http://upload.wikimedia.org/wikipedia/commons/d/da/Illu_endocrine_system.png gland