part of part of develops_from tissue endocrine system chordate pharynx primordium thyroid primordium AAO:0011106 BTO:0004709 EHDAA2:0002033 EHDAA:952 EMAPA:16361 In all vertebrates the thyroid arises from the ventral aspect of the second pouch Note that we follow EHDAA2 in dividing this into endoderm and mesenchyme. In this ontology we place the broad developmental relationship at this level, and include specific relationships to the pharyngeal endoderm at the level of the endoderm Portion of tissue part of the pharyngeal endoderm that is fated to become thyroid follicle[ZFIN:curator]. TAO:0001081 The initial thyroid precursor, the thyroid primordium, starts as a simple midline thickening and develops to form the thyroid diverticulum. This structure is initially hollow, although it later solidifies and becomes bilobed. The 2 lobes are located on either side of the midline and are connected via an isthmus. UBERON:0003091 UMLS:C1519512 XAO:0000444 ZFA:0001081 thyroid primordia uberon endoderm-derived structure pharyngeal pouch 2