Thyroid Gland

Thyroid Gland

1. Location and Structure

   • Upper, anterior part of neck
   • Anteriorly wrapped around trachea
   • Inferior of larynx
   • Extends down from thyroid cartilage to 6th tracheal ring
   • 2 lobes- connected by median tissue= isthmus (2nd to 4th tracheal ring)

2. Function

   • secretes thyroid hormones which controls:
     • basal metabolic rate
     • Carb, lipid and protein metabolism
   • Produces Calcitonin
     • Ca+ and P metabolism

3. Blood supply

   • R & L superior thyroid artery branches of the R&L external carotid artery
   • R & L inferior thyroid artery branches of the R & L thyrocervical trunk
   • Thyroid ima artery (not common)
   • Venous drainage 3 pairs of veins:
     • superior and middle thyroid veins
     • inferior thyroid veins
     • Drains into superior vena cava

4. Embryology

   • Epithelial proliferation in floor of pharynx
     • Gland descends infront of pharynx
   • initially connected to tongue via narrow canal
   • descends further to below thyroid cartilage
   • final position in 7th week (2 lobes and isthmus
     • function at end of 3rd month