ABSTRACT
The normal thyroid gland weighs 20-25 g. The functioning unit is the lobule supplied by a single arteriole and consisting of 24-40 follicles lined with cuboidal epithelium. The follicle contains colloid in which thyroglobulin is stored (Fig. 48.2). The arterial supply is rich, and extensive anastomoses occur between the main thyroid arteries and branches of the tracheal and oesophageal arteries (Fig. 48.3). There is an extensive lymphatic network within the gland. Although some lymph channels pass directly to the deep cervical nodes, the subcapsular plexus drains principally to the central compartment juxtathyroid nodes – ‘Delphian’ (level 6) –
paratracheal nodes (level 7) and nodes on the superior and inferior thyroid veins, and from there to the deep cervical (levels 2, 3, 4 and 5) and mediastinal groups of nodes.
