The thyroid gland normally lies in relation to the upper rings of the trachea. It is composed of two lateral lobes and an isthmus. At times an additional central or pyramidal lobe is present. This central lobe is connected with the point of origin of the fetal thyroid, that is, the foramen caecum (fig. 1). The connecting anatomic structure is the obliterated thyroglossal duct. At any place along this structure accessory or aberrant thyroid tissue may be encountered (fig. 2).
About the fourth week of intra-uterine life there appears in the midline of the embryo, immediately posterior to the tuberculum impar, a diverticulum which at first is hollow, but later becomes solid. This diverticulum grows downward and eventually becomes the thyroid gland. The upper extremity forms the foramen caecum; the lower in about 40 per cent of cases is characterized by a so-called pyramidal lobe of the gland.1
ZIEGELMAN EF. LINGUAL GOITER. Arch Otolaryngol. 1932;16(4):496–505. doi:10.1001/archotol.1932.00630040508003
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